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1.  ASSOCIATION OF ISOMETRIC STRENGTH OF HIP AND KNEE MUSCLES WITH INJURY RISK IN HIGH SCHOOL CROSS COUNTRY RUNNERS 
Background
High school cross country runners have a high incidence of overuse injuries, particularly to the knee and shin. As lower extremity strength is modifiable, identification of strength attributes that contribute to anterior knee pain (AKP) and shin injuries may influence prevention and management of these injuries.
Purpose
To determine if a relationship existed between isometric hip abductor, knee extensor and flexor strength and the incidence of AKP and shin injury in high school cross country runners.
Materials/Methods
Sixty‐eight high school cross country runners (47 girls, 21 boys) participated in the study. Isometric strength tests of hip abductors, knee extensors and flexors were performed with a handheld dynamometer. Runners were prospectively followed during the 2014 interscholastic cross country season for occurrences of AKP and shin injury. Bivariate logistic regression was used to examine risk relationships between strength values and occurrence of AKP and shin injury.
Results
During the season, three (4.4%) runners experienced AKP and 13 (19.1%) runners incurred a shin injury. Runners in the tertiles indicating weakest hip abductor (chi‐square = 6.140; p=0.046), knee extensor (chi‐square = 6.562; p=0.038), and knee flexor (chi‐square = 6.140; p=0.046) muscle strength had a significantly higher incidence of AKP. Hip and knee muscle strength was not significantly associated with shin injury.
Conclusions
High school cross country runners with weaker hip abductor, knee extensor and flexor muscle strength had a higher incidence of AKP. Increasing hip and knee muscle strength may reduce the likelihood of AKP in high school cross country runners.
Level of Evidence
2b
PMCID: PMC4637921  PMID: 26618066
Lower extremity muscle strength; medial tibial stress syndrome; patellofemoral pain syndrome; running
2.  Reliability and Validity of the Anterior Knee Pain Scale: Applications for Use as an Epidemiologic Screener 
PLoS ONE  2016;11(7):e0159204.
A screening instrument’s ability to provide clinicians with consistent and reproducible information is crucial to intervention. Despite widespread acceptance and clinical use of the Kujala Anterior Knee Pain Scale (AKPS) in orthopedics and sports medicine, few studies have reported on its reliability and no such studies have concentrated on child or adolescent samples exclusively, segments of the population for which this instrument is often used. The purpose of the current study was to describe and report on the reliability and validity of the AKPS for use with high school female athletes participating in interscholastic athletics. The study was a secondary analysis of prospective epidemiologic data using established scale validation methods. The records of 414 female athletes 11.0 to 18.1 years of age (Mean 13.9 yrs, SD = 1.7 yrs) were used for analysis. Four different approaches to scoring and scale reduction of the AKPS were evaluated, including the original, ordinal 13-item form, a modified, ordinal 6-item form, a modified, dichotomous 13-item form, and a modified, dichotomous 6-item form. Three different types of reliability (internal consistency, equivalence across forms, standard error of measurement) and one type of validity (criterion-related) were estimated for the AKPS in the current sample. The four scoring formats of the AKPS scale were found to have high internal consistency (αcoef = 0.83 to 0.91), equivalence across the short and long forms (r = 0.98), acceptable standard errors of measurement (0.82 to 3.00), and moderate to high criterion related validity—as determined by physican’s diagnosis: 0.92 (13-item form), 0.90 (6-item form). The Kujala AKPS is a valid and reliable measure of anterior knee pain and appropriate for use as an epidemiologic screening tool with adolescent female athletes.
doi:10.1371/journal.pone.0159204
PMCID: PMC4956048  PMID: 27441381
3.  PAIN, FUNCTION, AND STRENGTH OUTCOMES FOR MALES AND FEMALES WITH PATELLOFEMORAL PAIN WHO PARTICIPATE IN EITHER A HIP/CORE- OR KNEE-BASED REHABILITATION PROGRAM 
Background
Hip exercise has been recommended for females with patellofemoral pain (PFP). It is unknown if males with PFP will benefit from a similar treatment strategy.
Hypotheses/Purpose
The purpose of this study was to compare improvements in pain, function, and strength between males and females with PFP who participated in either a hip/core or knee rehabilitation program. The directional hypothesis was that females would respond more favorably to the hip/core rehabilitation program and males to the knee program.
Study Design
Randomized-controlled clinical trial
Methods
Patients were randomly assigned to a six-week hip/core or knee rehabilitation program. Visual analog scale (VAS), Anterior Knee Pain Scale (AKPS), and hip and knee isometric strength were collected before and after subjects completed the rehabilitation program. Data were analyzed using an intention-to-treat basis. Separate mixed-model analyses of variance (ANOVA) with repeated measures were used to determine changes in VAS and AKPS and strength changes for subjects classified as treatment responders (successful outcome) and non-responders (unsuccessful outcome).
Results
Regardless of sex or rehabilitation group, VAS (F1,181=206.5; p<.0001) and AKPS (F1,181 = 160.4; p < 0.0001) scores improved. All treatment responders demonstrated improved hip abductor (F1,122 = 6.6; p = 0.007), hip extensor (F1,122 = 19.3; p < 0.0001), and knee extensor (F1,122 = 16.0; p < 0.0001) strength. A trend (F1,122 = 3.6; p = 0.06) existed for an effect of sex on hip external rotator strength change. Males demonstrated a 15.4% increase compared to a 5.0% increase for females. All treatment non-responders had minimal and non-significant (p > 0.05) strength changes.
Conclusion
On average, males and females with PFP benefitted from either a hip/core or knee rehabilitation program. Subjects with successful outcomes likely had hip and knee weakness that responded well to the intervention. These males and females had similar and meaningful improvements in hip extensor and knee extensor strength. Only males had relevant changes in hip external rotator strength. Clinicians should consider a subgroup of males who may benefit from hip extensor and external rotator exercise and females who may benefit from hip extensor exercise.
Level of Evidence
2b
PMCID: PMC5095944  PMID: 27904794
Anterior knee pain; hip; rehabilitation; sex
4.  Effect of virgin olive oil versus piroxicam phonophoresis on exercise-induced anterior knee pain 
Objective:
The main purpose of this study was to evaluate the effects of virgin olive oil phonophoresis on female athletes' anterior knee pain (AKP).
Materials and Methods:
A double blinded randomized clinical trial was conducted. Ninety-three female athletes suffering from AKP voluntarily participated in this study. Patients were randomly assigned into olive oil (n=31), piroxicam (n=31) or base gel phonophoresis (n=31) groups. At the baseline visit, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire was filled by subjects who were then treated with olive oil, piroxicam or pure phonophoresis for 12 sessions. After 6 and 12 sessions of physiotherapy, subjects filled the questionnaire again. Main outcomes were significant improvement in pain, stiffness, physical function, and total WOMAC scores.
Results:
Although, there was a significant reduction in symptoms of AKP at the end of the therapy in all groups (p<0.05), but in olive oil group, this improvement was seen after 6 sessions of treatment (p<0.001). A significant difference between olive oil group and piroxicam and/or phonophoresis group was observed after 6 sessions of therapy (p<0.05).
Conclusion:
It could be proposed that phonophoresis with virgin olive oil is as effective as piroxicam gel on lowering WOMAC scores of AKP in female athletes and also has several beneficial properties including faster effect and shorter duration of therapy. The exact mechanism of beneficial action of virgin olive oil on AKP is not clear and requires further studies.
PMCID: PMC5052416  PMID: 27761423
Phonophoresis; Olive oil; Piroxicam; Anterior Knee Pain; Topical application
5.  KINEMATIC DETERMINANTS OF ANTERIOR KNEE PAIN IN CEREBRAL PALSY, A CASE_CONTROL STUDY 
Objective
To quantify the role patellofemoral and tibiofemoral kinematics may play in development of anterior knee pain (AKP) in individuals with cerebral palsy (CP).
Design
Case-Control
Setting
Clinical Research Center
Participants
Twenty knees from individuals diagnosed with CP and 40 control knees were evaluated. Controls were matched for sex and age based on the group average. Matching by height and weight was a secondary priority. Subjects in the control cohort were asymptomatic with no history of lower leg abnormality, surgery, or major injury. Only individuals who were physically capable of sustaining slow cyclic knee flexion-extension for 2.5 minutes and had no contraindications to MR imaging were enrolled. Both groups were samples of convenience.
Interventions
Not applicable.
Main Outcome Measure
The 3D patellofemoral and tibiofemoral joint kinematics, acquired during active leg extension, under volitional control.
Results
Participants with CP and AKP (n=8) demonstrated significantly greater patellofemoral extension, valgus rotation, superior, and posterior displacement relative to controls and to the subgroup of participants with CP and no AKP (n=12). Patellofemoral extension discriminated AKP in individuals with CP with 100% accuracy.
Conclusions
In quantifying the 3D in vivo knee joint kinematics during a volitional extension task, kinematic markers that discriminate AKP in individuals with CP were identified. This provides an ability to predict which individuals with CP are most likely to advance into AKP and could enable aggressive conservative treatment, aimed at reducing patella alta and excessive PF extension to be prescribed prior to considering surgical options. The current findings will likely lead to improved clinical diagnostics and interventions for individuals with CP, with the ultimate goal of helping maintain, if not improve functional mobility throughout the lifespan.
doi:10.1016/j.apmr.2012.03.022
PMCID: PMC3568741  PMID: 22465585
MRI; patellofemoral; tibiofemoral; dynamics
6.  Quadriceps Activation Following Knee Injuries: A Systematic Review 
Journal of Athletic Training  2010;45(1):87-97.
Abstract
Context:
Arthrogenic muscle inhibition is an important underlying factor in persistent quadriceps muscle weakness after knee injury or surgery.
Objective:
To determine the magnitude and prevalence of volitional quadriceps activation deficits after knee injury.
Data Sources:
Web of Science database.
Study Selection:
Eligible studies involved human participants and measured quadriceps activation using either twitch interpolation or burst superimposition on patients with knee injuries or surgeries such as anterior cruciate ligament deficiency (ACLd), anterior cruciate ligament reconstruction (ACLr), and anterior knee pain (AKP).
Data Extraction:
Means, measures of variability, and prevalence of quadriceps activation (QA) failure (<95%) were recorded for experiments involving ACLd (10), ACLr (5), and AKP (3).
Data Synthesis:
A total of 21 data sets from 18 studies were initially identified. Data from 3 studies (1 paper reporting data for both ACLd and ACLr, 1 on AKP, and the postarthroscopy paper) were excluded from the primary analyses because only graphical data were reported. Of the remaining 17 data sets (from 15 studies), weighted mean QA in 352 ACLd patients was 87.3% on the involved side, 89.1% on the uninvolved side, and 91% in control participants. The QA failure prevalence ranged from 0% to 100%. Weighted mean QA in 99 total ACLr patients was 89.2% on the involved side, 84% on the uninvolved side, and 98.5% for the control group, with prevalence ranging from 0% to 71%. Thirty-eight patients with AKP averaged 78.6% on the involved side and 77.7% on the contralateral side. Bilateral QA failure was commonly reported in patients.
Conclusions:
Quadriceps activation failure is common in patients with ACLd, ACLr, and AKP and is often observed bilaterally.
doi:10.4085/1062-6050-45.1.87
PMCID: PMC2808760  PMID: 20064053
arthrogenic muscle inhibition; voluntary activation; twitch interpolation; superimposed burst; central activation ratio
7.  Changes in Health-Related Quality of Life and Knee Function After Knee Injury in Young Female Athletes 
Orthopaedic Journal of Sports Medicine  2014;2(4):2325967114530988.
Background:
Recent literature has called for greater attention to evidence-based practice in sports medicine with the documentation of overall status and impairments following injury. The prospective documentation of impairments associated with knee injuries in female athletes regarding their health-related quality of life (HRQoL) and knee function (KF) of high school and collegiate athletes is limited. Assessing the effect knee injuries have on young female athletes may allow clinicians to better understand the perspectives of the athletes who sustain these injuries.
Purpose:
To document the changes over 12 months in self-reported HRQoL and KF in young females who have sustained a knee injury.
Study Design:
Case series; Level of evidence, 4.
Methods:
A convenience sample of 242 females (mean age, 17.4 ± 2.4 years) who injured their knee participating in sport or recreational activities was utilized. Injuries were categorized as anterior cruciate ligament tears (ACL), anterior knee pain (AKP), patellar instability (PAT), meniscus tear (MNT), iliotibial band syndrome (ITB), collateral ligament sprain (COL), and other (OTH). HRQoL was assessed with the Short Form–12 v 2.0 survey (SF-12) physical component summary (PCS) and mental component summary (MCS). KF was assessed with the 2000 International Knee Documentation Committee survey (IKDC). Dependent variables included the paired differences in the 2000 IKDC as well as SF-12 composite scores from preinjury through 12 months postdiagnosis. Paired differences were assessed with repeated-measures analyses of variance (P ≤ .05).
Results:
IKDC scores were lower through 12 months for ACL, AKP, and PAT; through 6 months for MNT; and through 3 months for COL and OTH. HRQoL PCS and MCS scores were lower through 3 to 12 months depending on the type of injury classification.
Conclusion:
Knee injuries can negatively affect KF and HRQoL for up to 12 months in young females. Sports medicine providers need to be aware of these impacts as they work to effectively treat individuals with these injuries.
doi:10.1177/2325967114530988
PMCID: PMC4555590  PMID: 26535324
female; knee injury; knee function; quality of life
8.  Is Body Composition Associated With An Increased Risk of Developing Anterior Knee Pain in Adolescent Female Athletes? 
Objective
To determine the relationship between relative body composition and body mass to height, anterior knee pain, or patellofemoral pain (PFP) in adolescent female athletes.
Background
Patellofemoral pain is common in female athletes and has an undefined etiology. The purpose of this study was to examine whether there was an association among higher body mass index (BMI), BMI z-scores, and relative body fat percentage in the development of PFP in an adolescent female athlete population. We hypothesized that female athletes who developed PFP over the course of a competitive basketball season had higher relative body mass or body fat percentage compared with those who did not develop PFP.
Methods
Fifteen middle school basketball teams that consisted of 248 basketball players (mean age, 12.76 ± 1.13 years; height, 158.43 ± 7.78 cm; body mass, 52.35 ± 12.31 kg; BMI, 20.73 ± 3.88 kg/m2) agreed to participate in this study over the course of 2 basketball seasons, resulting in 262 athlete-seasons. Testing included the completion of the Anterior Knee Pain Scale (AKPS), International Knee Documentation Committee (IKDC) form, standardized history, physician-administered physical examination, maturational estimates, and anthropometrics.
Results
Of the 262 athlete-seasons monitored, 39 athletes developed PFP over the course of the study. The incidence rate of new PFP was 1.57 per 1000 athlete-exposures. The cumulative incidence of PFP was 14.9%. There was no difference in BMI between those who developed PFP (mean body mass, 20.2 kg/m2; 95% CI, 18.9–21.4) and those who did not develop PFP (mean body mass, 20.8 kg/m2; 95% CI, 20.3–21.3; P > 0.05). Body mass index z-scores were not different between those who developed PFP (mean, 0.3; 95% CI, 0.7–0.6) and those who did not develop PFP (mean, 0.4; 95% CI, 0.3–0.6; P > 0.05). A similar trend was noted in relative body fat percentage, with mean scores of similar ranges in those who developed PFP (mean body fat percentage, 22.2%; 95% CI, 19.4–24.9) to the referent group who did not (mean body fat percentage, 22.9%; 95% CI, 21.8–24.1; P > 0.05).
Conclusions
Our results do not indicate a relationship between relative body composition or relative body mass to height to the propensity to develop PFP in middle school–aged female basketball players. Although previous data indicate a relationship between higher relative body mass and overall knee injury, these data did not support this association with PFP specifically. These data suggest the underlying etiology of PFP may be neuromuscular in nature. Further research is needed to understand the predictors, etiology, and ultimate prevention of this condition.
doi:10.3810/psm.2012.02.1947
PMCID: PMC3398745  PMID: 22508247
patellofemoral pain; anterior knee pain; biomechanics; body mass index; BMI z-score; anthropometrics; body fat; patellofemoral pain
9.  Anterior knee pain following total knee replacement correlates with the OARSI score of the cartilage of the patella 
Acta Orthopaedica  2014;85(4):427-432.
Background
Attempts to relate patellar cartilage involvement to anterior knee pain (AKP) have yielded conflicting results. We determined whether the condition of the cartilage of the patella at the time of knee replacement, as assessed by the OARSI score, correlates with postsurgical AKP.
Patients and methods
We prospectively studied 100 patients undergoing knee arthroplasty. At surgery, we photographed and biopsied the articular surface of the patella, leaving the patella unresurfaced. Following determination of the microscopic grade of the patellar cartilage lesion and the stage by analyzing the intraoperative photographs, we calculated the OARSI score. We interviewed the patients 1 year after knee arthroplasty using the HSS patella score for diagnosis of AKP.
Results
57 of 95 patients examined had AKP. The average OARSI score of painless patients was 13 (6–20) and that of patients with AKP was 15 (6–20) (p = 0.04). Patients with OARSI scores of 13–24 had 50% higher risk of AKP (prevalence ratio = 1.5, 95% CI: 1.0–2.3) than patients with OARSI scores of 0–12.
Interpretation
The depth and extent of the cartilage lesion of the knee-cap should be considered when deciding between the various options for treatment of the patella during knee replacement.
doi:10.3109/17453674.2014.931198
PMCID: PMC4105776  PMID: 24954482
10.  Treatment of refractory anterior knee pain using botulinum toxin type A (Dysport) injection to the distal vastus lateralis muscle: a randomised placebo controlled crossover trial 
Objectives
This randomised controlled crossover trial examined the efficacy of botulinum toxin type A (BoNT-A) injection, plus an exercise programme, to remediate chronic anterior knee pain (AKP) associated with quadriceps muscle imbalance.
Methods
24 individuals with refractory AKP received either BoNT-A (500 U Dysport) or the same volume saline injection to the vastus lateralis (VL) muscle and performed home exercises focusing on re-training the vastus medialis (VM) muscle. All subjects were offered open-label injection at 12 weeks. Knee-related disability (anterior knee pain scale; AKPS) and activity-induced pain (10 cm visual analogue scale) at 12 weeks were the primary outcomes. Peak isometric extensor force was recorded and normalised VL:VM ratios were derived from simultaneous surface electromyography. Selfreported pain and disability measures were collected at six time points to a mean of 20±8 months.
Results
14 subjects received BoNT-A and 10 placebo injection. Improvement at 12 weeks was significantly greater for BoNT-A compared with placebo-injected subjects for the AKPS (p<0.03), pain on kneeling (p<0.004), squatting (p<0.02) and level walking (p<0.04). At week 12, five placebo subjects crossed over to open-label injection. At 24 weeks, 16 of 19 BoNT-A-injected and two of the remaining five placeboinjected subjects were either satisfied or very satisfied with treatment outcomes. Improvements were maintained in 11 of 14 BoNT-A-injected and two of five placebo subjects available at longer-term follow-up.
Conclusion
BoNT-A injection produced a greater reduction in pain and disability than placebo injection in carefully selected patients with chronic AKP related to quadriceps muscle imbalance.
doi:10.1136/bjsm.2009.069781
PMCID: PMC3106976  PMID: 20418523
11.  The relative timing of VMO and VL in the aetiology of anterior knee pain: a systematic review and meta-analysis 
Background
Anterior knee pain (AKP) is a common musculoskeletal complaint. It has been suggested that one factor that may contribute to the presence of AKP is a delay in the recruitment of the vastus medialis oblique muscle (VMO) relative to the vastus lateralis muscle (VL). There is however little consensus within the literature regarding the existence or nature of any such delay in the recruitment of the VMO within the AKP population. The purpose of this systematic review and meta-analysis was to examine the relative timing of onset of the VMO and VL in those with AKP in comparison to the asymptomatic population.
Methods
The bibliographic databases AMED, British Nursing Index, CINAHL, EMBASE, Ovid Medline, PEDro, Pubmed and the Cochrane Library were searched for studies comparing the timing of EMG onset of the VMO and VL in those with AKP versus the asymptomatic population. Studies fulfilling the inclusion criteria were independently assessed. Heterogeneity across the studies was measured. A meta-analysis of results was completed for those studies where adequate data was supplied. Where comparable methodologies had been used, results were pooled and analysed.
Results
Fourteen studies met the inclusion criteria; one prospective and thirteen observational case control. Eleven compared VMO and VL EMG onset times during voluntary active tasks while four investigated reflex response times. All used convenience sampling and did not state blinding of the assessor. Study methodologies/testing and assessment procedures varied and there was considerable heterogeneity within individual samples. Whilst a trend was identified towards a delay in onset of VMO relative to the VL in the AKP population during both voluntary active tasks and reflex activity, a substantial degree of heterogeneity across the pooled studies was identified (I2 = 69.9–93.4%, p < 0.01).
Conclusion
Findings are subject to substantial and unexplained heterogeneity. A trend was demonstrated towards a delayed onset of VMO relative to VL in those with AKP in comparison to those without. However not all AKP patients demonstrate a VMO-VL dysfunction, and this is compounded by normal physiological variability in the healthy population. The clinical and therapeutic significance is therefore difficult to assess.
doi:10.1186/1471-2474-9-64
PMCID: PMC2386790  PMID: 18452611
12.  Anterior knee pain in younger adults as a precursor to subsequent patellofemoral osteoarthritis: a systematic review 
Background
Patellofemoral osteoarthritis (PFOA) is a common form of knee OA in middle and older age, but its relation to PF disorders and symptoms earlier in life is unclear. Our aim was to conduct a systematic review to investigate the strength of evidence for an association between anterior knee pain (AKP) in younger adults and subsequent PFOA.
Methods
The search strategy included electronic databases (Pubmed, EMBASE, AMED, CINAHL, Cochrane, PEDro, SportDiscus: inception to December 2009), reference lists of potentially eligible studies and selected reviews. Full text articles in any language, - identified via English titles and abstracts, were included if they were retrospective or prospective in design and contained quantitative data regarding structural changes indicative of PFOA, incident to original idiopathic AKP. Eligibility criteria were applied to titles, abstracts and full-texts by two independent reviewers. Data extraction included study location, design, date, sampling procedure, sample characteristics, AKP/PFOA definitions, follow-up duration and rate, and main findings. Foreign language articles were translated into English prior to examination.
Results
Seven articles satisfied eligibility (5 English, 2 German). Only one case-control study directly investigated a link between PFOA and prior AKP, providing level 3b evidence in favour of an association (OR 4.4; 95%CI 1.8, 10.6). Rough estimates of the annual risk of PFOA from the remaining six small, uncontrolled, observational studies (mean follow-up range: 5.7 to 23 years) ranged from 0% to 3.4%. This was not the primary aim of these studies, and limitations in design and methodology mean this data should be interpreted with caution.
Conclusions
There is a paucity of high-quality evidence reporting a link between AKP and PFOA. Further, well-designed cohort studies may be able to fill this evidence gap.
doi:10.1186/1471-2474-11-201
PMCID: PMC2944218  PMID: 20828401
13.  The effectiveness of neuromuscular warm-up strategies, that require no additional equipment, for preventing lower limb injuries during sports participation: a systematic review 
BMC Medicine  2012;10:75.
Background
Lower limb injuries in sport are increasingly prevalent and responsible for large economic as well as personal burdens. In this review we seek to determine which easily implemented functional neuromuscular warm-up strategies are effective in preventing lower limb injuries during sports participation and in which sporting groups they are effective.
Methods
Seven electronic databases were searched from inception to January 2012 for studies investigating neuromuscular warm-up strategies and injury prevention. The quality of each included study was evaluated using a modified version of the van Tulder scale. Data were extracted from each study and used to calculate the risk of injury following application of each evaluated strategy.
Results
Nine studies were identified including six randomized controlled trials (RCT) and three controlled clinical trials (CCT). Heterogeneity in study design and warm-up strategies prevented pooling of results. Two studies investigated male and female participants, while the remaining seven investigated women only. Risk Ratio (RR) statistics indicated 'The 11+' prevention strategy significantly reduces overall (RR 0.67, confidence interval (CI) 0.54 to 0.84) and overuse (RR 0.45, CI 0.28 to 0.71) lower limb injuries as well as knee (RR 0.48, CI 0.32 to 0.72) injuries among young amateur female footballers. The 'Knee Injury Prevention Program' (KIPP) significantly reduced the risk of noncontact lower limb (RR 0.5, CI 0.33 to 0.76) and overuse (RR 0.44, CI 0.22 to 0.86) injuries in young amateur female football and basketball players. The 'Prevent Injury and Enhance Performance' (PEP) strategy reduces the incidence of anterior cruciate ligament (ACL) injuries (RR 0.18, CI 0.08 to 0.42). The 'HarmoKnee' programme reduces the risk of knee injuries (RR 0.22, CI 0.06 to 0.76) in teenage female footballers. The 'Anterior Knee Pain Prevention Training Programme' (AKP PTP) significantly reduces the incidence of anterior knee pain (RR 0.27, CI 0.14 to 0.54) in military recruits.
Conclusions
Effective implementation of practical neuromuscular warm-up strategies can reduce lower extremity injury incidence in young, amateur, female athletes and male and female military recruits. This is typically a warm-up strategy that includes stretching, strengthening, balance exercises, sports-specific agility drills and landing techniques applied consistently for longer than three consecutive months. In order to optimize these strategies, the mechanisms for their effectiveness require further evaluation.
doi:10.1186/1741-7015-10-75
PMCID: PMC3408383  PMID: 22812375
neuromuscular training; lower limb; injuries; prevention
14.  EVALUATION OF A TREATMENT ALGORITHM FOR PATIENTS WITH PATELLOFEMORAL PAIN SYNDROME: A PILOT STUDY 
Background:
Treatment of patellofemoral pain syndrome (PFPS) has been extensively studied in physical therapy literature. Patients with PFPS demonstrate quadriceps and hip musculature weakness, altered lower extremity (LE) kinematics, and decreased LE flexibility. Psychosocial factors have also been identified as an important factor in patients with PFPS. The authors hypothesize that an ordered approach addressing each of these impairments sequentially will result in greater improvement in PFPS symptoms. The purpose of this pilot study was to assess the feasibility of performing a randomized trial and to determine the sample size necessary to examine the validity of this hypothesis.
Methods:
Patients received a sequential treatment approach using a PFPS treatment algorithm (PFPS Algorithm) designed by the authors. Patients were evaluated assessing psychosocial factors, flexibility, LE kinematics, and LE strength. Impairments that were found in the evaluation were addressed sequentially over the episode of care. Patients were prescribed therapy two times per week for six weeks. Pain, Anterior Knee Pain Scale (AKPS), and Global Rating of Change (GROC) were measured at evaluation and discharge.
Results:
Thirty consecutive patients with PFPS who were referred to physical therapy were enrolled in the pilot study. All phases of the feasibility study including recruitment, treatment protocols and data collection were effectively carried out. One hundred percent of patients treated with the PFPS algorithm who completed the prescribed treatment had a clinically significant improvement in the AKPS and GROC. A floor effect was noted with NPRS with 38% of patients unable to achieve clinically significant improvement.
Conclusions:
With minor changes to the protocol and outcome measures used, a full randomized trial is feasible and merited. Steps must be taken to reduce the high drop‐out rate among both groups.
Level of Evidence:
1b
PMCID: PMC4387725  PMID: 25883866
Patellofemoral pain; knee pain; physical therapy
15.  Precise nail tip positioning after tibial intramedullary nailing prevents anterior knee pain 
International Orthopaedics  2013;37(8):1527-1531.
Purpose
Anterior knee pain (AKP) is a common complication following intramedullary nailing of tibial shaft fractures. Our aim was, by analysing the postoperative lateral knee X-rays and clinical status (VAS score), to find the best intramedullary tip position of a non protruded nail that will provide the best postoperative outcome avoiding AKP.
Methods
We evaluated the postoperative outcome of 221 patients, from the last four years, with healed fractures initially treated with intramedullary reamed nails with two or three interlocking screws proximally and distally through a medial paratendinous incision for nail entry portal. Our aim was to analyse a possible relationship between AKP according to the VAS scale, and nail position marked as a distance from tip of nail to tibial plateau (NP) and to tibial tuberosity (NT), measured postoperatively on lateral knee X-rays.
Results
Two groups of patients were formed on the basis of presence of pain related to AKP (the level of pain was neglected): group A were patients with pain and group B without pain. The difference between the two groups concerning NP and NT measurements appeared to be statistically significant concerning NT measurement (p < 0.05), with high accuracy according to the classification tree.
Conclusions
We presume that the position of the proximal tip of the nail and its negative influence on the innervation pattern of the area dorsal to patellar tendon could be the key factor of AKP. We conclude that the symptoms of AKP will not appear if the tip of the nail position is more than 5.5 mm from the tibial plateau (NP) and more than 2.5 mm from the tibial tuberosity (NT).
doi:10.1007/s00264-013-1944-z
PMCID: PMC3728407  PMID: 23754779
16.  Neuromuscular training and muscle strengthening in patients with patellofemoral pain syndrome: a protocol of randomized controlled trial 
Background
Patellofemoral pain syndrome (PFPS) is a common musculoskeletal condition, particularly among women. Patients with PFPS usually experience weakness in the gluteal muscles, as well as pain and impaired motor control during activities of daily living. Strengthening the hip muscles is an effective way of treating this disorder. Neuromuscular training has also been identified as a therapeutic tool, although the benefits of this intervention in patients with PFPS patients remain inconclusive.
Design
This is a protocol of randomized controlled trial with a blind assessor. Thirty-four women with a clinical diagnosis of PFPS participated. These participants were allocated into two groups (experimental and control). The experimental group performed twelve sessions to strengthen the knee extensors, hip abductor and lateral rotator muscles in association with neuromuscular training of the trunk and lower extremities. The control group performed the same number of sessions to strengthen the muscles of the hip and knee. The primary outcome was functional capacity (Anterior Knee Pain Scale – AKPS) at 4 weeks. Pain intensity, muscle strength and kinematic changes were also measured during the step down test after four weeks of intervention. Follow up assessments were conducted after three and six months to assess functional capacity and pain. The effects of the treatment (i.e. between-group differences) were calculated using mixed linear models.
Discussion
The present study was initiated on the 1st of April 2013 and is currently in progress. The results of this study may introduce another effective technique of conservative treatment and could guide physical therapists in the clinical decision-making process for women with PFPS.
Trial registration
Current Controlled Trials NCT01804608.
doi:10.1186/1471-2474-15-157
PMCID: PMC4036089  PMID: 24884455
Biomechanics; Kinematics; Anterior knee pain; Hip; Knee; Neuromuscular
17.  The Diagnostic Performance of Anterior Knee Pain and Activity-related Pain in Identifying Knees with Structural Damage in the Patellofemoral Joint: The Multicenter Osteoarthritis Study 
The Journal of rheumatology  2014;41(8):1695-1702.
Objective
To determine the diagnostic test performance of location of pain and activity-related pain in identifying knees with patellofemoral joint (PFJ) structural damage.
Methods
The Multicenter Osteoarthritis Study is a US National Institutes of Health-funded cohort study of older adults with or at risk of knee osteoarthritis. Subjects identified painful areas around the knee on a knee pain map and the Western Ontario and McMaster Universities Osteoarthritis Index was used to assess pain with stairs and walking on level ground. Cartilage damage and bone marrow lesions were assessed from knee magnetic resonance imaging. We determined the sensitivity, specificity, positive and negative predictive values for presence of anterior knee pain (AKP), pain with stairs, absence of pain while walking on level ground, and combinations of tests in discriminating knees with isolated PFJ structural damage from those with isolated tibiofemoral joint (TFJ) or no structural damage. Knees with mixed PFJ/TFJ damage were removed from our analyses because of the inability to determine which compartment was causing pain.
Results
There were 407 knees that met our inclusion criteria. “Any” AKP had a sensitivity of 60% and specificity of 53%; and if AKP was the only area of pain, the sensitivity dropped to 27% but specificity rose to 81%. Absence of moderate pain with walking on level ground had the greatest sensitivity (93%) but poor specificity (13%). The combination of “isolated” AKP and moderate pain with stairs had poor sensitivity (9%) but the greatest specificity (97%) of strategies tested.
Conclusion
Commonly used questions purported to identify knees with PFJ structural damage do not identify this condition with great accuracy.
doi:10.3899/jrheum.131555
PMCID: PMC4182011  PMID: 24931959
OSTEOARTHRITIS; PAIN; MAGNETIC RESONANCE IMAGING
18.  Anterior knee pain after a total knee arthroplasty: What can cause this pain? 
World Journal of Orthopedics  2014;5(3):163-170.
Total Knee Arthroplasty has been shown to be a successful procedure for treating patients with osteoarthritis, and yet approximately 5%-10% of patients experience residual pain, especially in the anterior part of the knee. Many theories have been proposed to explain the etiology of this anterior knee pain (AKP) but, despite improvements having been made, AKP remains a problem. AKP can be described as retropatellar or peripatellar pain, which limits patients in their everyday lives. Patients suffering from AKP experience difficulty in standing up from a chair, walking up and down stairs and riding a bicycle. The question asked was: “How can a ‘perfectly’ placed total knee arthroplasty (TKA) still be painful: what can cause this pain?”. To prevent AKP after TKA it is important to first identify the different anatomical structures that can cause this pain. Greater attention to and understanding of AKP should lead to significant pain relief and greater overall patient satisfaction after TKA. This article is a review of what pain is, how nerve signalling works and what is thought to cause Anterior Knee Pain after a Total Knee Arthroplasty.
doi:10.5312/wjo.v5.i3.163
PMCID: PMC4095008  PMID: 25035818
Anterior knee pain; Patellofemoral pain; Total knee arthroplasty; Malrotation; Homeostasis
19.  A Novel Association between Femoroacetabular Impingement and Anterior Knee Pain 
Pain Research and Treatment  2015;2015:937431.
Background. For a long time it has been accepted that the main problem in the anterior knee pain (AKP) patient is in the patella. Currently, literature supports the link between abnormal hip function and AKP. Objective. Our objective is to investigate if Cam femoroacetabular impingement (FAI) resolution is related to the outcome in pain and disability in patients with chronic AKP recalcitrant to conservative treatment associated with Cam FAI. Material and Methods. A retrospective study on 7 patients with chronic AKP associated with FAI type Cam was performed. Knee and hip pain were measured with the visual analogue scale (VAS), knee disability with the Kujala scale, and hip disability with the Nonarthritic Hip Score (NAHS). Results. The VAS knee pain score and VAS hip pain score had a significant improvement postoperatively. At final follow-up, there was significant improvement in all functional scores (Kujala score and NAHS). Conclusion. Our finding supports the link between Cam FAI and AKP in some young patients. Assessment of Cam FAI should be considered as a part of the physical examination of patients with AKP, mainly in cases with pain recalcitrant to conservative treatment.
doi:10.1155/2015/937431
PMCID: PMC4584218  PMID: 26451254
20.  Does patellofemoral congruence following total knee arthroplasty correlate with pain or function? Intraoperative arthroscopic assessment of 30 cases 
Background
Anterior knee pain (AKP) is observed in total knee arthroplasty (TKA) both with and without patellar resurfacing, and neither patellar denervation nor secondary resurfacing are effective for treating the symptoms. The exact causes for pain remain unclear, though abnormal patellofemoral forces due to patellar malalignment or inadequate implant design can play an important role. The purpose of this study was to arthroscopically evaluate patellofemoral congruence after wound closure following TKA without patellar resurfacing and correlate it to patellar morphology and postoperative pain and function.
Methods
The authors prospectively studied 30 patients that received uncemented mobile-bearing TKA. Patellofemoral congruence was assessed arthroscopically after wound closure by estimating the contact area between the native patella and the prosthetic trochlea (> two-thirds, > one-third, < one-third). The findings were correlated to preoperative assessments of patellar geometry (Wiberg classification using X-rays) and clinical outcomes [Knee Society Score (KSS), AKP on Visual Analogic Scale (VAS), and patient satisfaction].
Results
Knees of 22 women and 8 men aged 69.8 years (range, 61–84 years) were analyzed at 16 months (range, 12–23 months). Preoperative patellar geometry was Wiberg type A in 11, type B in 12 and type C in 7 knees. Postoperative KSS was 79.1 (range, 50.0–94) and the VAS for AKP was 1.6±1.3 (median, 1; range, 0–5). Patellar congruence was correlated with patellar morphology (P<0.001) but not correlated with any clinical outcomes (KSS, VAS or satisfaction). There were also no statistical correlations between patellar morphology or patellofemoral congruence and patient characteristics.
Conclusions
While patellar morphology and patellofemoral congruence are strongly related, they are not associated with clinical outcomes or patient demographics. Considering that numerous incongruent patellofemoral joints were pain-free, and conversely, many perfectly congruent patellofemoral joints had anterior pain, the authors suppose that pain is probably caused by mechanisms other than patellofemoral pressures.
doi:10.21037/atm.2016.07.21
PMCID: PMC4980378  PMID: 27570773
Total knee arthroplasty (TKA); patellar morphology; Wiberg type; patellofemoral congruence; anterior knee pain (AKP)
21.  Patellar Osteoid Osteoma as a Cause of Anterior Knee Pain in Adolescents: A Case Report and Literature Review 
Case Reports in Medicine  2013;2013:746472.
Anterior Knee Pain (AKP) is an important cause of complaint in adolescents which can suggest many possible diseases. Scientific literature concerning this complex symptom is wide and diversified. We report a rare case of patellar osteoid osteoma which affected a thirteen-year-old female who had suffered from anterior left knee pain for almost six months. The diagnosis was suspected from an accurate anamnesis, a careful clinical examination, and confirmed by imaging. Several minimally invasive techniques can be employed to treat osteoid osteoma. However, we consider CT-guided percutaneous drilling the safest and most effective procedure in case of patellar location. Despite its rarity, patellar osteoid osteoma ranges in the differential diagnosis for all patients suffering from AKP.
doi:10.1155/2013/746472
PMCID: PMC3608179  PMID: 23554815
22.  The incidence of trochlear dysplasia in anterior cruciate ligament tears 
International Orthopaedics  2014;38(6):1269-1275.
Purpose
The purpose of the present epidemiologic study is to record the radiographic presence of trochlear dysplasia and patella alta in patients who undergo anterior cruciate ligament (ACL) reconstruction as a potential underlying factor for post-operative anterior knee pain (AKP).
Methods
All consecutive cases of skeletally-mature ACL-deficient knees that would undergo ACL reconstruction in three different hospitals were prospectively included during a six-month period. Inclusion criteria were acute and sub-acute ACL injury with no previous ipsilateral knee operation. Patients with chronic ACL tears, prior-to-ACL-injury history of patellar instability or other PF disorders were excluded from the study.
Results
A total of 299 knees were included (mean age 32 ± ten years). Forty-four (14.7 %) knees had a positive ‘crossing sign’ in the lateral X-rays and 255 (85.3 %) had no sign of trochlear dysplasia (p < 0.01). Among the cases with trochlear dysplasia, 41 (93 %) had type A trochlear dysplasia with the presence only of the ‘crossing sign’ and three (7 %) had type C trochlear dysplasia. Patellar height results included a mean Caton-Deschamps index of 1.0 ± 0.14 (0.5–1.4). Twenty (6.6 %) knees had an index of less than 0.8, and two (0.6 %) knees had an index less than 0.6. In contrast, 15 (5.0 %) knees had an abnormal value of more than 1.2, indicating patella alta.
Conclusions
The most important finding of the study is the increased prevalence of trochlear dysplasia and patella alta in patients with ACL injury, when compared to the incidence of trochlear dysplasia and patella alta in the general population in the literature. This finding could sound as an alert of a possible additional risk factor for post-operative anterior knee pain after ACL reconstruction.
doi:10.1007/s00264-014-2291-4
PMCID: PMC4037506  PMID: 24515227
Anterior cruciate ligament; Trochlear dysplasia; Patella alta; Anterior knee pain; Patellofemoral
23.  Study protocol: a randomised controlled trial comparing the long term effects of isolated hip strengthening, quadriceps-based training and free physical activity for patellofemoral pain syndrome (anterior knee pain) 
Background
Patellofemoral pain syndrome (PFPS), also known as Anterior Knee Pain, is a common cause of recurrent or chronic knee pain. The etiology is considered to be multifactorial but is not completely understood. At the current time the leading theory is that pathomechanics in the patellofemoral joint leads to PFPS. Traditionally, conservative treatment has focused on improving strength and timing in the quadriceps muscles. In recent years, evidence has been accumulating to support the importance of hip control and strengthening in PFPS. Two recent studies have shown promising results for hip strengthening as an isolated treatment for PFPS. The aim of this randomised contolled trial (RCT) is to compare isolated hip strengthening to traditional quadriceps-based training and a control group with free physical activity.
Methods/Design
An observer-blinded RCT will be performed. We intend to include 150 patients aged 16–40 years, referred from primary care practitioners to the department of Physical Medicine and Rehabilitation in Kristiansand, Norway for PFPS with more than three months duration. Patients meeting the inclusion criteria will be randomised using opaque sequentially numbered sealed envelopes to one of three groups: isolated hip strengthening, quadriceps based training, or a control group (free physical activity). All groups will receive standardized information about PFPS formulated with the intention to minimize fear avoidance and encourage self-mastery of symptoms. Standardized exercises will be performed under supervision of a study physiotherapist once per week in addition to home training two times per week for a total of six weeks. The primary outcome measure will be the Anterior Knee Pain Score (AKPS) at three and 12 months. Secondary outcome measures will include Visual analogue scale (VAS) for pain, hip abductor and quadriceps strength, the generic EuroQol (EQ-5D), Hopkins Symptom Checklist (HSCL), Knee self-efficacy score and Tampa score for Kinesiophobia.
Discussion
This trial will help to elucidate the role of hip and quadriceps strengthening in the treatment of PFPS. Information as to the role of anxiety and depression, kinesiophobia and self-efficacy will be collected, also as regards prognosis and response to exercise therapy.
Trial registration
ClinicalTrials.gov reference: NCT02114294.
doi:10.1186/s12891-015-0493-6
PMCID: PMC4342827  PMID: 25879452
Patellofemoral pain syndrome; Anterior knee pain; Exercise therapy; Hip strengthening
24.  The Australia-modified Karnofsky Performance Status (AKPS) scale: a revised scale for contemporary palliative care clinical practice [ISRCTN81117481] 
Background
The Karnofsky Performance Status (KPS) is a gold standard scale. The Thorne-modified KPS (TKPS) focuses on community-based care and has been shown to be more relevant to palliative care settings than the original KPS. The Australia-modified KPS (AKPS) blends KPS and TKPS to accommodate any setting of care.
Methods
Performance status was measured using all three scales for palliative care patients enrolled in a randomized controlled trial in South Australia. Care occurred in a range of settings. Survival was defined from enrollment to death.
Results
Ratings were collected at 1600 timepoints for 306 participants. The median score on all scales was 60. KPS and AKPS agreed in 87% of ratings; 79% of disagreements occurred within 1 level on the 11-level scales. KPS and TKPS agreed in 76% of ratings; 85% of disagreements occurred within one level. AKPS and TKPS agreed in 85% of ratings; 87% of disagreements were within one level. Strongest agreement occurred at the highest levels (70–90), with greatest disagreement at lower levels (≤40). Kappa coefficients for agreement were KPS-TKPS 0.71, KPS-AKPS 0.84, and AKPS-TKPS 0.82 (all p < 0.001). Spearman correlations with survival were KPS 0.26, TKPS 0.27 and AKPS 0.26 (all p < 0.001). AKPS was most predictive of survival at the lower range of the scale. All had longitudinal test-retest validity. Face validity was greatest for the AKPS.
Conclusion
The AKPS is a useful modification of the KPS that is more appropriate for clinical settings that include multiple venues of care such as palliative care.
doi:10.1186/1472-684X-4-7
PMCID: PMC1308820  PMID: 16283937
25.  To Resurface or Not to Resurface the Patella in Total Knee Arthroplasty 
The management of the patellar articular surface at the time of primary total knee arthroplasty (TKA) is controversial. We used expected-value decision analysis to determine whether the patella should be resurfaced in TKA, and also whether secondary resurfacing on an unresurfaced patella is worthwhile. Outcome probabilities and utility values were derived from randomized controlled trials only. A decision tree was constructed and fold-back analysis was performed to ascertain the best treatment path. Sensitivity analyses were performed to determine the effect on decision-making of varying outcome probabilities and utilities. Our model showed patellar resurfacing is the best management strategy for the patella at the time of primary TKA. This decision is robust to changes in the specific data: the best path would remain the same as long as the incidence of persistent anterior knee pain (AKP) with resurfacing remains less than 29% (current mean, 12%) or the incidence of AKP after nonresurfacing falls below 12% (current mean, 26%). Delayed (ie, secondary) patellar resurfacing for ongoing patellar pain provides inferior results for the majority of patients.
Level of Evidence: Level II, decision analysis. See the Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-008-0420-3
PMCID: PMC2565036  PMID: 18726657

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