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To quantify the role patellofemoral and tibiofemoral kinematics may play in development of anterior knee pain (AKP) in individuals with cerebral palsy (CP).
Clinical Research Center
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.
Not applicable.
Main Outcome Measure
The 3D patellofemoral and tibiofemoral joint kinematics, acquired during active leg extension, under volitional control.
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.
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.
PMCID: PMC3568741  PMID: 22465585
MRI; patellofemoral; tibiofemoral; dynamics
2.  Quadriceps Activation Following Knee Injuries: A Systematic Review 
Journal of Athletic Training  2010;45(1):87-97.
Arthrogenic muscle inhibition is an important underlying factor in persistent quadriceps muscle weakness after knee injury or surgery.
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.
Quadriceps activation failure is common in patients with ACLd, ACLr, and AKP and is often observed bilaterally.
PMCID: PMC2808760  PMID: 20064053
arthrogenic muscle inhibition; voluntary activation; twitch interpolation; superimposed burst; central activation ratio
3.  Is Body Composition Associated With An Increased Risk of Developing Anterior Knee Pain in Adolescent Female Athletes? 
To determine the relationship between relative body composition and body mass to height, anterior knee pain, or patellofemoral pain (PFP) in adolescent female athletes.
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.
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.
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).
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.
PMCID: PMC3398745  PMID: 22508247
patellofemoral pain; anterior knee pain; biomechanics; body mass index; BMI z-score; anthropometrics; body fat; patellofemoral pain
4.  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.
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.
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.
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.
PMCID: PMC4105776  PMID: 24954482
5.  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 
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.
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.
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.
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.
PMCID: PMC3106976  PMID: 20418523
6.  The relative timing of VMO and VL in the aetiology of anterior knee pain: a systematic review and meta-analysis 
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.
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.
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).
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.
PMCID: PMC2386790  PMID: 18452611
7.  Anterior knee pain in younger adults as a precursor to subsequent patellofemoral osteoarthritis: a systematic review 
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.
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.
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.
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.
PMCID: PMC2944218  PMID: 20828401
8.  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.
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.
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.
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.
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.
PMCID: PMC3408383  PMID: 22812375
neuromuscular training; lower limb; injuries; prevention
9.  Precise nail tip positioning after tibial intramedullary nailing prevents anterior knee pain 
International Orthopaedics  2013;37(8):1527-1531.
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.
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.
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.
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).
PMCID: PMC3728407  PMID: 23754779
10.  Neuromuscular training and muscle strengthening in patients with patellofemoral pain syndrome: a protocol of randomized controlled trial 
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.
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.
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.
PMCID: PMC4036089  PMID: 24884455
Biomechanics; Kinematics; Anterior knee pain; Hip; Knee; Neuromuscular
11.  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.
To determine the diagnostic test performance of location of pain and activity-related pain in identifying knees with patellofemoral joint (PFJ) structural damage.
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.
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.
Commonly used questions purported to identify knees with PFJ structural damage do not identify this condition with great accuracy.
PMCID: PMC4182011  PMID: 24931959
12.  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.
PMCID: PMC4095008  PMID: 25035818
Anterior knee pain; Patellofemoral pain; Total knee arthroplasty; Malrotation; Homeostasis
13.  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.
PMCID: PMC3608179  PMID: 23554815
14.  The Australia-modified Karnofsky Performance Status (AKPS) scale: a revised scale for contemporary palliative care clinical practice [ISRCTN81117481] 
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.
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.
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.
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.
PMCID: PMC1308820  PMID: 16283937
15.  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.
PMCID: PMC2565036  PMID: 18726657
16.  Hip and Knee Strength Is Not Affected in 12-16 Year Old Adolescents with Patellofemoral Pain - A Cross-Sectional Population-Based Study 
PLoS ONE  2013;8(11):e79153.
One of the rationales behind using strength training in the treatment of adolescents with Patellofemoral Pain (PFP) is that reduced strength of the lower extremity is a risk factor for PFP and a common deficit. This rationale is based on research conducted on adolescents >15 years of age but has never been investigated among young adolescents with PFP.
To compare isometric muscle strength of the lower extremity among adolescents with PFP compared to age- and gender-matched pain-free adolescents.
In 2011 a population-based cohort (APA2011-cohort) consisting of 768 adolescents aged 12–15 years from 8 local schools was formed. In September 2012, all adolescents who reported knee pain in September 2011 were offered a clinical examination if they still had knee pain. From these, 20 adolescents (16 females) were diagnosed with PFP. Pain-free adolescents from the APA2011-cohort (n = 20) were recruited on random basis as age- and gender-matched pairs. Primary outcome was isometric knee extension strength normalized to body weight (%BW) and blinded towards subject information. Secondary outcomes included knee flexion, hip abduction/adduction and hip internal/external rotation strength. Demographic data included Knee Injury and Osteoarthritis Outcome Score (KOOS) and symptom duration.
Adolescents with PFP reported long symptom duration and significantly worse KOOS scores compared to pain-free adolescents. There were no significant differences in isometric knee extension strength (Δ0.3% BW, p = 0.97), isometric knee flexion strength (Δ0.4% BW, p = 0.84) or different measures of hip strength (Δ0.4 to 1.1% BW, p>0.35).
Young symptomatic adolescents with PFP between 12 and 16 years of age did not have decreased isometric muscle strength of the knee and hip. These results question the rationale of targeting strength deficits in the treatment of adolescents with PFP. However, strength training may still be an effective treatment for those individuals with PFP suffering from strength deficits.
PMCID: PMC3827322  PMID: 24236101
17.  Patellar Taping, Patellofemoral Pain Syndrome, Lower Extremity Kinematics, and Dynamic Postural Control 
Journal of Athletic Training  2008;43(1):21-28.
Context: Patellar taping has been a part of intervention for treatment of patellofemoral pain syndrome (PFPS). However, research on the efficacy of patellar taping on lower extremity kinematics and dynamic postural control is limited.
Objective: To evaluate the effects of patellar taping on sagittal-plane hip and knee kinematics, reach distance, and perceived pain level during the Star Excursion Balance Test (SEBT) in individuals with and without PFPS.
Design: Repeated-measures design with 2 within-subjects factors and 1 between-subjects factor.
Setting: The University of Toledo Athletic Training Research Laboratory.
Patients or Other Participants: Twenty participants with PFPS and 20 healthy participants between the ages of 18 and 29 years.
Intervention(s): The participants performed 3 reaches of the SEBT in the anterior direction under tape and no-tape conditions on both legs.
Main Outcome Measure(s): The participants' hip and knee sagittal-plane kinematics were measured using the electromagnetic tracking system. Reach distance was recorded by hand and was normalized by dividing the distance by the participants' leg length (%MAXD). After each taping condition on each leg, the participants rated the perceived pain level using the 10-cm visual analog scale.
Results: The participants with PFPS had a reduction in pain level with patellar tape application compared with the no-tape condition (P = .005). Additionally, participants with PFPS demonstrated increased %MAXD under the tape condition compared with the no-tape condition, whereas the healthy participants demonstrated decreased %MAXD with tape versus no tape (P = .028). No statistically significant differences were noted in hip flexion and knee flexion angles.
Conclusions: Although patellar taping seemed to reduce pain and improve SEBT performance of participants with PFPS, the exact mechanisms of these phenomena cannot be explained in this study. Further research is warranted to investigate the effect of patellar taping on neuromuscular control during dynamic postural control.
PMCID: PMC2231393  PMID: 18335009
anterior knee pain; McConnell taping
18.  Preoperative easily misdiagnosed telangiectatic osteosarcoma: clinical–radiologic–pathologic correlations 
Cancer Imaging  2013;13(4):520-526.
Purpose: To describe the clinical, imaging, and pathologic characteristics and diagnostic methods of telangiectatic osteosarcoma (TOS) for improving the diagnostic level. Materials and methods: The authors retrospectively reviewed patient demographics, serum alkaline phosphatase (AKP) levels, preoperative biopsy pathologic reports, pathologic materials, imaging findings, and treatment outcomes from 26 patients with TOS. Patient images from radiography (26 cases) and magnetic resonance (MR) imaging (22 cases) were evaluated by 3 authors in consensus for intrinsic characteristics. There were 15 male and 11 female patients in the study, with an age of 9–32 years (mean age 15.9 years). Results: Eighteen of 26 patients died of lung metastases within 5 years of follow-up. The distal femur was affected more commonly (14 cases, 53.8%). Regarding serum AKP, normal (8 cases) or mildly elevated (18 cases) levels were found before preoperative chemotherapy. Radiographs showed geographic bone lysis without sclerotic margin (26 cases), cortical destruction (26 cases), periosteal new bone formation (24 cases), soft-tissue mass (23 cases), and matrix mineralization (4 cases). The aggressive radiographic features of TOS simulated the appearance of conventional high-grade intramedullary osteosarcoma, though different from aneurysmal bone cyst. MR images demonstrated multiple big (16 cases) or small (6 cases) cystic spaces, fluid-fluid levels (14 cases), soft-tissue mass (22 cases), and thick peripheral and septal enhancement (22 cases). Nine of 26 cases were misdiagnosed as aneurysmal bone cysts by preoperative core-needle biopsy, owing to the absence of viable high-grade sarcomatous cells in the small tissue samples. Conclusion: The aggressive growth pattern with occasional matrix mineralization, and multiple big or small fluid-filled cavities with thick peripheral, septal, and nodular tissue surrounding the fluid-filled cavities are characteristic imaging features of TOS, and these features are helpful in making the correct preoperative diagnosis of TOS.
PMCID: PMC3864225  PMID: 24334494
Telangiectatic osteosarcoma; magnetic resonance imaging; radiography; pathology; biopsy
19.  The Patella Pro study — effect of a knee brace on patellofemoral pain syndrome: design of a randomized clinical trial (DRKS-ID:DRKS00003291) 
Patellofemoral pain syndrome (PFPS) is a frequent cause of anterior knee pain predominantly affecting young female patients who do not have significant chondral damage. Development of PFPS is probably multifactorial, involving various knee, hip, and foot kinematic factors. Biomechanical studies have described patellar maltracking and dynamic valgus (functional malalignment) in patients with patellofemoral pain syndrome. The literature provides evidence for short-term use of nonsteroidal anti-inflammatory drugs; short-term medially directed taping; and exercise programs focusing on the lower extremity, hip, and trunk muscles. Evidence supporting the use of patellar braces is limited because previous studies have been low quality. The aim of this article is to publish the design of a prospective randomized trial that examines the outcomes of patients with PFPS after treatment with a new patellar brace (Patella Pro) that applies medially directed force on the patella.
For this multicenter trial, 156 patients (adolescents and young adults) with PFPS were recruited from orthopedic practices and orthopedic hospitals and randomly allocated to 3 months of supervised physiotherapy in combination with the Patella Pro brace or supervised physiotherapy alone. The primary outcome measures are pain (numerical analog scale); knee function (Kujala score and Knee Injury and Osteoarthritis Outcome Score); and self-reported perception of recovery at baseline, 6 weeks, 3 months, and 1 year.
Only limited evidence for the use of a patellar brace for the treatment of PFPS exists in the literature. Disputable evidence for the use of orthoses for PFPS patients has been presented in one meta-analysis, in which only one of three studies found the effect of a medially directed patellar brace to be significant. Because of these low-quality studies, the authors concluded that this evidence should be regarded as limited, and we feel there is a need for further well-designed studies to evaluate the effect of patellar bracing on PFPS-related pain. The Patella Pro study is a prospective randomized trial in which supervised physiotherapy in combination with a patellar brace is compared with supervised physiotherapy alone. This trial started in April 2012 and finished in October 2013.
Trial registration
DRKS-ID:DRKS00003291, January 3rd, 2012
PMCID: PMC4089925  PMID: 24917049
Patellar maltracking; Dynamic valgus; Anterior knee pain; Functional malalignment; Chondromalacia patellae; Patellar orthosis; Patellar tape
20.  Reduced functional performance in the lower extremity predicted radiographic knee osteoarthritis five years later 
Annals of the Rheumatic Diseases  2004;63(4):402-407.
Background: Reduced quadriceps strength is an early finding in subjects with knee osteoarthritis, but it is not clear whether it is a cause or a consequence of knee osteoarthritis.
Objective: To determine whether reduced functional performance in the lower extremity predicts the incidence or progression of radiographic knee osteoarthritis.
Design: Prospective, epidemiological, population based cohort study.
Patients: 148 subjects (62 women), aged 35–54 (mean 44.8), with chronic knee pain from a population based cohort.
Measurements: Predictors analysed were age, sex, body mass index, baseline knee pain, and three tests of lower extremity functional performance: maximum number of one-leg rises from sitting, time spent walking 300 m, and timed standing on one leg. Weightbearing tibiofemoral knee radiographs were obtained at baseline and after 5 years (median 5.1, range 4.2–6.1), and classified according to Kellgren and Lawrence as no osteoarthritis (Kellgren and Lawrence = 0, n = 94) or prevalent osteoarthritis (Kellgren and Lawrence ⩾1, n = 54).
Results: Fewer one-leg rises (median 17 v 25) predicted incident radiographic osteoarthritis five years later (OR 2.6, 95% CI 1.1 to 6.0). The association remained significant after controlling for age, sex, body mass index, and pain. No significant predictor of radiographic progression in the group with prevalent osteoarthritis was found.
Conclusion: Reduced functional performance in the lower extremity predicted development of radiographic knee osteoarthritis 5 years later among people aged 35–55 with chronic knee pain and normal radiographs at baseline. These findings suggest that a test of one-leg rises may be useful, and interventions aimed at improving functional performance may be protective against development of knee osteoarthritis.
PMCID: PMC1754965  PMID: 15020334
21.  Hydronephrosis due to pelviureteric junction narrowing: Utility of urinary enzymes to predict the need for surgical management and follow-up 
To study the role of urinary enzymes N-acetyl-β-glucosaminidase (NAG), alkaline phosphatase (AKP) and gamma glutamyl transferase (GGT) in the diagnosis and follow-up of patients with suspected pelviureteric junction obstruction (PUJO).
Materials and Methods:
A total of 70 patients, 29 managed conservatively (group A) and 41 managed by pyeloplasty (group B), were studied prospectively. A serial measurement of urinary enzymes NAG, AKP and GGT level was performed in both the groups. The mean levels of these urinary enzymes were compared between the two groups and among the patients of the same group at presentation as well as during follow-up.
There was a significant fall in the mean AKP level in patients managed conservatively at 8 months of follow-up. Similarly, in the operated group, there was a significant fall in the AKP levels at both 3 months and 8 months of follow-up. The mean level of GGT also showed a significant fall after 3 months of surgery but did not show further significant change at 8 months after surgery. The mean levels of NAG and GGT in the conservatively managed group were significantly low compared with that of patients requiring pyeloplasty at presentation as well as in the follow-up. The mean level of AKP was significantly low in the conservatively managed group when compared with the patients requiring surgery, but did not differ significantly in both the follow-ups after surgery.
The level of urinary enzymes NAG, AKP and GGT are significantly high in the patients with hydronephrosis (HDN) requiring pyeloplasty when compared with the patients managed conservatively. The level of AKP significantly falls after pyeloplasty in the patients of HDN due to PUJO. There is a negative correlation with the preoperative level of enzyme NAG with split renal function in the patients of HDN requiring pyeloplasty.
PMCID: PMC3263031  PMID: 22279355
Alkaline phosphatase; gamma glutamyl transferase; N-acetyl-β-glucosaminidase; pelviureteric junction obstruction; urinary biomarkers; urinary enzymes
22.  Sex Differences in Valgus Knee Angle During a Single-Leg Drop Jump 
Journal of Athletic Training  2006;41(2):166-171.
Context: Sex differences in lower extremity landing mechanics and muscle activation have been identified as potential causative factors leading to the increased incidence of anterior cruciate ligament injuries in female athletes. Valgus knee alignment places greater strain on the anterior cruciate ligament than a more neutral alignment. Gluteus medius (GM) activation may stabilize the leg and pelvis during landing, limiting valgus knee motion and potentially preventing anterior cruciate ligament injury.
Objective: To determine if frontal-plane knee angle and GM activation differ between the sexes at initial contact and maximal knee flexion during a single-leg drop landing.
Design: Between-groups design.
Setting: Motion analysis laboratory.
Patients or Other Participants: Thirty-two healthy subjects between the ages of 18 and 30 years.
Intervention(s): The independent variables were sex (male or female) and position (initial contact or maximal knee flexion).
Main Outcome Measure(s): Frontal-plane knee angle and GM average root mean square (aRMS) amplitude.
Results: At initial contact, women landed in knee valgus and men landed in knee varus ( P < .025). At maximal knee flexion, both men and women were in a position of knee varus, but the magnitude of varus was less in women than in men ( P < .025). The GM aRMS amplitude was greater at maximal knee flexion than at initial contact ( P < .025); however, male GM aRMS did not differ from female GM aRMS amplitude at either position ( P > .025).
Conclusions: Women tended to land in more knee valgus before and at impact than men. The GM muscle activation did not differ between the sexes and, thus, does not appear to be responsible for the sex differences in knee valgus. The excessive valgus knee angles displayed in women may help to explain the sex disparity in anterior cruciate ligament injury.
PMCID: PMC1472649  PMID: 16791301
biomechanics; kinematics; landing; electromyography; anterior cruciate ligament
23.  Expected Prevalence From the Differential Diagnosis of Anterior Knee Pain in Adolescent Female Athletes During Preparticipation Screening 
Journal of Athletic Training  2012;47(5):519-524.
Anterior knee pain is a common disorder in female athletes with an undefined cause. The relative prevalence of specific patellofemoral disorders associated with anterior knee pain in adolescent females remains undetermined.
To determine the prevalence of specific patellofemoral disorders obtained using the differential diagnosis of anterior knee pain in adolescent female athletes during preparticipation screening.
Descriptive epidemiology study.
Preparticipation screening evaluations at a county public school district in Kentucky.
Patients or Other Participants
A total of 419 unique middle and high school–aged female athletes.
Main Outcome Measure(s)
Participants were evaluated by physicians for anterior knee pain over 3 consecutive basketball seasons. Given the longitudinal nature of this study, some participants were tested longitudinally over multiple years.
Over the course of 3 basketball seasons, 688 patient evaluations were performed. Of these, 183 (26.6%) were positive for anterior knee pain. A statistically significant difference was noted in the prevalence of anterior knee pain by school level, with 34.4% (n = 67) in high school–aged athletes versus 23.5% (n = 116) in middle school–aged athletes (P < .05). In the 1376 knees evaluated, patellofemoral dysfunction was the most common diagnosis, with an overall prevalence of 7.3% (n = 100). The only diagnosis shown to be statistically different between age levels was Sinding-Larsen-Johansson disease or patellar tendinopathy, with 38 cases (9.7%) in high school–aged and 31 (3.1%) in middle school–aged athletes (P < .05).
Anterior knee pain was present in 26.6% of the adolescent female athletes screened over 3 years. Symptoms of anterior knee pain likely persist after middle school–aged onset and reach peak prevalence during the high school years.
PMCID: PMC3465032  PMID: 23068589
patellofemoral disorders; biomechanics; plica; Osgood-Schlatter disease; patellar tendinopathy
24.  Effects of Mild and Severe Knee Joint Pain on Various Activities of Daily Living in the Female Elderly 
Pain Research and Treatment  2013;2013:989508.
This study aimed to examine the differences in the ability to perform various activities of daily living (ADLs) among groups with various knee problems. The participants consisted of 328 elderly females (age 60–94; mean age 76.1 years; standard deviation 6.2). The subjects were classified into three groups: those without knee pain, those with mild knee pain, and those with severe knee pain. ADLs with markedly higher (>97%) and lower (<38%) achievement rates in the group without knee pain were not significantly different among the three groups. Achievement rates of 40%–97% for ADLs were significantly lower in the group with severe knee pain than in the group without knee pain. In addition, the groups with mild and severe knee pain demonstrated significantly lower achievement rates of ascending and descending stairs and sitting up than the group without knee pain. In conclusion, regardless of the presence of absence of mild or severe knee pain, some ADLs are difficult to achieve, while others are easy. The elderly with severe knee pain find it difficult to achieve many ADLs. In addition, it is difficult for the elderly with mild and severe knee pain to ascend and descend stairs and to sit up.
PMCID: PMC3809357  PMID: 24224088
25.  High knee abduction moments are common risk factors for patellofemoral pain (PFP) and anterior cruciate ligament (ACL) injury in girls: Is PFP itself a predictor for subsequent ACL injury? 
Identifying risk factors for knee pain and anterior cruciate ligament (ACL) injury can be an important step in the injury prevention cycle.
We evaluated two unique prospective cohorts with similar populations and methodologies to compare the incidence rates and risk factors associated with patellofemoral pain (PFP) and ACL injury.
The ‘PFP cohort’ consisted of 240 middle and high school female athletes. They were evaluated by a physician and underwent anthropometric assessment, strength testing and three-dimensional landing biomechanical analyses prior to their basketball season. 145 of these athletes met inclusion for surveillance of incident (new) PFP by certified athletic trainers during their competitive season. The ‘ACL cohort’ included 205 high school female volleyball, soccer and basketball athletes who underwent the same anthropometric, strength and biomechanical assessment prior to their competitive season and were subsequently followed up for incidence of ACL injury. A one-way analysis of variance was used to evaluate potential group (incident PFP vs ACL injured) differences in anthropometrics, strength and landing biomechanics. Knee abduction moment (KAM) cut-scores that provided the maximal sensitivity and specificity for prediction of PFP or ACL injury risk were also compared between the cohorts.
KAM during landing above 15.4 Nm was associated with a 6.8% risk to develop PFP compared to a 2.9% risk if below the PFP risk threshold in our sample. Likewise, a KAM above 25.3 Nm was associated with a 6.8% risk for subsequent ACL injury compared to a 0.4% risk if below the established ACL risk threshold. The ACL-injured athletes initiated landing with a greater knee abduction angle and a reduced hamstrings-to-quadriceps strength ratio relative to the incident PFP group. Also, when comparing across cohorts, the athletes who suffered ACL injury also had lower hamstring/quadriceps ratio than the players in the PFP sample (p<0.05).
In adolescent girls aged 13.3 years, >15 Nm of knee abduction load during landing is associated with greater likelihood of developing PFP. Also, in girls aged 16.1 years who land with >25 Nm of knee abduction load during landing are at increased risk for both PFP and ACL injury.
PMCID: PMC4182160  PMID: 24687011

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