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N Am J Sports Phys Ther. 2007 May; 2(2): 81–89.
PMCID: PMC2953293

Deconditioned Knee: The Effectiveness of a Rehabilitation Program that Restores Normal Knee Motion to Improve Symptoms and Function

K. Donald Shelbourne, MD,a Angela Biggs, PT, MS,a and Tinker Gray, MA, ELSa

Abstract

Background

Knee pain can cause a deconditioned knee. Deconditioned is defined as causing one to lose physical fitness. Therefore, a deconditioned knee is defined as a painful syndrome caused by anatomical or functional abnormalities that result in a knee flexion contracture (functional loss of knee extension), decreased strength, and decreased function. To date, no published studies exist examining treatment for a deconditioned knee.

Objective

To determine the effectiveness of a rehabilitation program focused on increasing range of motion for patients with a deconditioned knee.

Methods

Fifty patients (mean age 53.2 years) enrolled in the study. Objective evaluation included radiographs, knee range of motion, and isokinetic strength testing. The International Knee Documentation Committee (IKDC) subjective questionnaire was used to measure symptoms and function. Patients were given a rehabilitation program to increase knee extension (including hyperextension) and flexion equal to the normal knee, after which patients were instructed in leg strengthening exercises.

Results

Knee extension significantly improved from a mean deficit of 10° to 3° and knee flexion significantly improved from a mean deficit of 19° to 9°. The IKDC survey scores significantly improved from a mean of 34.5 points to 70.5 points 1 year after beginning treatment. The IKDC subjective pain frequency and severity scores were significantly improved.

Conclusions

A rehabilitation program that improves knee range of motion can relieve pain and improve function for patients with a deconditioned knee.

Keywords: knee pain, flexion contracture, range of motion

INTRODUCTION

Knee pain is a common complaint and reason for people to seek medical care by a primary care physician or an orthopaedic surgeon.13 Each year over 1 million emergency room visits and 1.9 million visits to primary care physicians are for complaints of knee pain.4 Knee pain can be caused by an acute knee injury, or many times, the pain is chronic and can progressively get worse with time. Approximately 30% of adults 65 years of age and older report knee pain or stiffness in the past 30 days. Sixty percent of adults 65 years and older and 37% of young adults age 20 to 44 report pain lasting 1 year or more, with the knee joint being the most common area of pain cited.5 People who have persistent knee pain often favor the painful knee. As a result, he or she may lose knee range of motion, develop a knee flexion contracture, and lose strength, which alters the normal function of the knee. Deconditioned means causing one to lose physical fitness. Therefore, a deconditioned knee is described as a painful syndrome caused by anatomical or functional abnormalities that result in a knee flexion contracture (functional loss of knee extension), decreased strength, and decreased function.

A deconditioned knee may occur from osteoarthritis or a knee that has not been completely rehabilitated after a surgery or injury. This condition may also result from extreme overuse, failed previous knee surgery, or from favoring one knee over the other for an extended period of time. Patients who develop a knee flexion contracture experience rehabilitation difficulty because a knee with a flexion contracture is difficult to strengthen. Patients are often treated with medication, braces, foot orthotics, or knee surgery.69 However, these treatment options do not specifically address the loss of knee range of motion.

Studies of patients with knee pain and osteoarthritis have shown that rehabilitation programs that include manual therapy, strengthening exercises, hydrotherapy, or general exercise can reduce pain and improve function.1014 Other similar studies have found no benefit from exercise programs15,16 or that exercises are most helpful when conducted in a supervised setting.17,18 According to the Philadelphia Panel systematic review on rehabilitation interventions for knee pain, transcutaneous electrical nerve stimulation (TENS) and therapeutic exercise were beneficial for knee osteoarthritis.19 However, a void remains in the literature demonstrating the effectiveness of specific therapeutic exercises correlated with a valid and reliable outcome measurement tool. In addition, no published literature exists that describes the effectiveness of increasing range of motion in the treatment of a deconditioned knee

Range of motion is a critical factor in determining the clinical outcome following total knee arthroplasty.2024 It is also an important factor following anterior cruciate ligament reconstruction. Research has shown that obtaining full knee hyperextension equal to the opposite normal knee is one of the most important factors in contributing to a successful outcome after anterior cruciate ligament reconstruction.2530 Even 3° to 5° of extension loss resulted in a poorer outcome.

In many text books, knee range of motion is described as 0° of extension and 135° of flexion.31,32 According to a study by De Carlo and Sell,33 however, 96% of the population has some degree of hyperextension. They found normal knee extension to be a mean of 5° of hyperextension in males and 6° of hyperextension in females.

Given that knee extension is an important factor in the success of surgical treatment, this study was performed to determine the relevance of full knee extension in the treatment of chronic knee conditions described as a deconditioned knee. No studies exist that have examined whether an improvement of knee range of motion to normal (equal to the opposite normal knee) can reduce subjective complaints of patients with chronic knee pain. Therefore, the purpose of this study was to determine the effectiveness of a rehabilitation program that focused on improving knee range of motion to treat patients with a deconditioned knee. The hypothesis to be tested was that patients who underwent rehabilitation to improve knee range of motion would have a statistically significant improvement in subjective knee pain scores.

METHODS

A power analysis was performed before the study began. An improvement of 10 points on the subjective knee questionnaire would be considered a clinical improvement. A sample size of 41 patients was required for a = 0.05 and power = 0.80.

Patients who complained of knee pain and had a lack of knee range of motion were prospectively asked to enroll in the study. To be included in the study, the patient had to have a knee flexion contracture of at least 5°, could not be taking any narcotic pain medication, and had to have an intact anterior cruciate ligament. Exclusion criteria included patients with bilateral knee pain or who had an injury or condition that would obviously explain pain or lack of knee range of motion (i.e. meniscus tear) and required surgical intervention. Patients signed a voluntary consent approved by the Institutional Review Board at Methodist Hospital in Indianapolis.

Radiographs were obtained at the initial visit and the posterior 45° flexed weightbearing view was used to evaluate for osteoarthritis.34 Patients attended physical therapy and were given a rehabilitation program that included exercises to restore full knee extension equal to the opposite normal knee first, followed by exercises to restore normal knee flexion. Light strengthening exercises were prescribed as needed when knee range of motion was restored, and the exercises included the stationary bike, single leg press, and single leg extension.

The IKDC (International Knee Documentation Committee) subjective survey was used to evaluate pain, activity, and knee function. The IKDC is a reliable, responsive and validated instrument used to assess symptoms, function, and sports activity in patients with a variety of knee disorders.35 In addition, normative data is available to assist in the interpretation of the subjective results.36 Patients were asked to complete the questionnaire independently in a private treatment room at the initial visit and at 1 and 3 months after initial treatment. The same questionnaire was sent in the mail to patients at 6 and 12 months after the initial visit.

Range of motion measurements were taken using a goniometer as described by Norkin and White.37 Range of motion measurements were recorded as A-B-C, with A being the degrees of hyperextension, B indicating lack of extension from zero, and C documenting the degrees of flexion. Measurements were taken by the treating physical therapist. Intra-tester and inter-tester reliability measurements of the treating therapists were high (kappa > 0.8) for both flexion and extension.38 Knee range of motion was recorded at the initial visit and at 1 and 3 months after the initial visit. The IKDC objective form grades range of motion as normal, nearly normal, abnormal, or severely abnormal. Range of motion was graded according to IKDC criteria (Table 1).

Table 1.
Grading of knee range of motion according to the criteria set by the International Knee Documentation Committee (IKDC).

Quadriceps muscle strength was evaluated by the treating physical therapist with isokinetic strength testing performed at 180°/sec at the 1 month and 3 month visit. The strength test was not performed at the initial visit because most patients' knees were too painful for them to tolerate the evaluation.

Patients who required surgical intervention for symptoms were considered a failure of rehabilitation treatment.

Rehabilitation Program

Patients were instructed and issued a home exercise program that focused on improving knee extension first. Patients were instructed in prone hang exercises, heel prop exercises, and towel extension stretches (Figure 1) to increase knee extension equal to the opposite normal knee. The patients were instructed to perform 10 repetitions of each exercise 3x/day. If patients were unable to achieve normal knee extension through the previous exercises, a hyperextension device (Elite Seat, Kneebourne Therapeutic, Noblesville, IN) (Figure 2) was utilized in addition to the other extension exercises. Patients were instructed to use the extension device for 10 minutes 3x/day.

Figure 1.
Towel stretch exercises. The patient holds on to the ends of a towel that is wrapped around the ball of the foot. While using one hand to hold the top part of the leg down on the table, the other hand pulls the ends of the towel so that the knee is hyperextended ...
Figure 2:
A knee extension device can be used to assist with applying downward pressure on the knee for extension. The patient places the straps across above and below the knee. The patient then lies supine to relax the hamstring muscles. A crank handle is used ...

In addition to exercises, patients were educated in daily habits to be performed throughout the day to help maintain knee extension gained by the exercises. These extension habits included performing heel prop exercises while sitting or standing on the involved extremity with the knee locked out forcing the knee into full hyperextension via an active quadriceps contraction (Figure 3). Improving knee extension remained the focus of the treatment until full hyperextension equal to the opposite knee was achieved. Patients were also encouraged to ice their knee for swelling and soreness as needed.

Figure 3:
This figure shows a good standing habit where the patient stands with full weight on the affected leg with the knee locked out into full hyperextension.

As knee extension improved towards normal, the exercise program was progressed to include flexion exercises if a deficit was present. The knee flexion exercises included heel slides while sitting and wall slides while lying supine; again, all exercises were performed at 10 repetitions 3x/day

Upon near full range of motion, patients were instructed to begin a low impact aerobic exercise such as the bike, elliptical, or stair-stepping machine. They were also instructed in light strengthening exercises including single leg press, leg extensions, quarter squats, and step down exercises. Patients were continually encouraged to maintain full range of motion while advancing their exercise program of low impact activity and leg strengthening exercises.

Data Analysis

Descriptive statistics were used to determine the mean knee range of motion at each visit and the mean IKDC subjective scores at each observation. Data analysis comparing pre-treatment and post-A knee extension device can be treatment subjective scores was The patient performed on patients who completed the study. Two-tailed t-test was used to determine whether a statistically significant difference existed between initial and final values for parametric data of IKDC total scores and isokinetic quadriceps muscle strength scores. Wilcoxon signed-rank test was used to determine whether there was a statistically significant difference between initial and final values for nonparametric data of knee extension, knee flexion, and IKDC pain frequency and severity scores. Repeated measures analysis of variance was used to determine if the IKDC total subjective scores improved through time after the initial visit. For all statistical analysis, the 0.5 level of probability was used. Due to the fact that six t tests were performed on this part of the study, a Boneferroni adjustment was performed, (0.05/6) thereby, set-ting the alpha level at p<0.008.

The IKDC subjective score of patients in this study was compared with normative IKDC data obtained by the IKDC committee.36 Anderson et al36 compiled normative data for 5,246 knees of men and women in four age groups (18-24 years, 25 to 34 years, 35 to 50 years, 51 to 65 years) and means for the groups were established. The investigators offered a formula for converting raw IKDC subjective scores to a standardized score that would give the standard deviation units above or below the population average, which was then applied to the present study group. A one sample t-test was performed to determine if the standardized IKDC score was significantly different than zero for each sex and age group. Again, the level of probability was set at p<0.05 and following a Bonneferoni correction due to four t tests (0.05/4), the alpha level was adjusted to p<0.013.

RESULTS

Fifty patients enrolled into the study; 42 patients completed the study and 8 patients were considered a failure of treatment because they underwent a surgical procedure by other physicians for their symptoms. The mean age of patients (25 men; 25 women) at the time of enrollment into the study was 53.2 ± 9.9 years (range 25.0 to 72.4) and no significant difference in age existed between men and women. The underlying pathology in the knee was osteoarthritis in 41 patients (Table 2), previous arthroscopy without rehabilitation in seven patients, and disuse osteoporosis in two patients.

Table 2.
Grade and compartment of osteoarthritis at time of initial evaluation

A statistically significant improvement was found in knee extension, knee flexion, and quadriceps muscle strength from initial evaluation to final follow-up (Table 3). At the initial evaluation, the mean range of motion in the non-involved knee was from 4° of hyperextension to 135° of flexion, and 44 of 50 patients had some degree of hyperextension in their normal knee (range 1° to 15°). The mean deficit in knee range of motion compared with the opposite normal knee was 10° of extension and 19° of flexion. The mean deficit in knee range of motion compared with the opposite normal knee was 10° of extension and 19° of flexion. The mean deficit in knee range of motion at final follow-up was 3° of extension and 9° of flexion, which was a statistically significant improvement for both extension and flexion (p<0.008). Twenty patients achieved what is considered normal knee extension (within 2° of the uninvolved knee). Sixteen patients achieved knee extension that is considered nearly normal (within 5° of the uninvolved knee), and six patients had abnormal extension (lacking 6° to 10° of extension compared to the uninvolved knee). All patients had improvement in knee extension and all but four patients had improvement in knee flexion. The mean improvement in extension was 6° (range 1° to 11°) and the mean improvement in flexion being 10° (range 0°−40°; Table 3).

Table 3.
Results summary

Eight patients were considered a failure of rehabilitation treatment because they had subsequently undergone surgical intervention for their symptoms. Three patients had a total knee arthroplasty, four patients had a knee arthroscopy, and one patient had a meniscal transplant. All eight patients, however, had improvement in knee extension (mean 5°, range 1 to 10°) and five of eight patients had improvement in flexion (mean 5°, range −5 to 15). Furthermore, the IKDC subjective scores improved from a mean of 30.8 ± 9.5 points to 45.7 ± 18.7 points, although this improvement is not statistically significant (p=0.0675).

International Knee Documentation Committee survey scores significantly improved with treatment from a mean of 34.5 ± 14.0 points to 70.5 ± 20.6 points (p<0.008). Repeated measures analysis of variance showed that the mean IKDC subjective scores significantly improved (p<0.008) through time with the greatest increase in scores being from the initial evaluation to the one month evaluation (Figure 4).

Figure 4:
The mean subjective scores improved through time with the greatest improvement obtained between the initial evaluation and one month follow-up.

The IKDC subjective survey evaluates both severity and frequency of pain on a scale of 0 to 10, with 0 being “no pain” and frequency as “never” and 10 being “worst pain imaginable” and “constant” frequency. The mean score of pain frequency significantly improved from 8.7 ± 3.3 points to 3.3 ± 2.8 points (p<0.008). Similarly, the mean score for pain severity significantly improved from 6.0 ± 2.0 points to 2.5 ± 2.3 points (p<0.008).

The final total IKDC subjective scores for the study group compared with normative data is shown in Table 4, which include the mean IKDC standardized score showing the standard deviation above or below the population average. The one sample t-test comparing the IKDC scores between the study group and normative data36 showed that no statistically significant difference existed for men or women in the different age groups (Table 4).

Table 4.
Final IKDC total scores compared with normative data .

DISCUSSION

The results of this study show the effectiveness of a rehabilitation program that focused on increasing range of motion equal to the opposite normal knee to improve subjective symptoms in patients with deconditioned knees. The results demonstrate the effectiveness of non-operative rehabilitation in treating a deconditioned knee. This particular study shows that knee pain and function can significantly improve by increasing knee range of motion and, in particular, knee extension.

The underlying knee pathology causing pain in many of the patients in this study was osteoarthritis. Most of these patients had been told by other physicians that they needed a total knee arthroplasty or arthroscopic procedure to alleviate their pain. However, 84% of the patients in this study improved with non-operative treatment. These results demonstrate that physical therapy can improve knee pain and function with non-operative treatment, which is an important factor considering rising health care costs. Non-operative treatment can be more effective and cost efficient to the patient and insurance companies.

Forty-two of 50 patients completed the study and 38 of 42 patients had improvement in knee extension, knee flexion, and subjective outcome measures. Only eight of the 50 patients (16%) dropped out of the study to undergo a surgical procedure. These eight patients all had some degree of improvement in knee extension, which is an important factor in determining the success after surgery. So, although eight patients underwent surgery, the improvement in range of motion obtained pre-operatively may help minimize post-operative range of motion complications.

When comparing the mean IKDC score from the study group to the normative data, there was no statistical difference for patients of the same sex and age group. This fact indicates that the rehabilitation program was effective for returning patients back to a normal level of function for their age group.

The loss of knee extension is common after knee surgery, knee injury, or knee pain. While recovering, it is a person's natural tendency to favor the involved extremity and stand with the involved knee bent, unless otherwise instructed to do so. Within a short period of time, even days, a person can develop a flexion contracture resulting in a loss of motion and subsequent loss of leg strength. Many times, the patient is unaware that a loss of knee extension has occurred because the deficit has come on gradually. A typical scenario is one where the patient has seen a physician for knee pain and has been told to reduce activities to accommodate the pain. While this habit can temporarily make the knee feel better, it does nothing to assist the patient with functioning normally with every day activities.

A thorough and accurate knee evaluation is critical to recognizing knee asymmetry. During evaluation, a flexion contracture can often be observed when the patient is lying supine on the table. When the patient is unable to fully extend the knee, he or she must externally rotate the hip (Figure 5). Another way to observe the patient is during standing. Patients with a flexion contracture will typically stand with the involved knee bent and most of their weight is placed on the non-involved leg. These observation techniques alert the clinician to the possible presence of a flexion contracture. In addition to taking goniometric measurements, it is important to asses the passive end feel of knee extension (Figure 6). Examining the normal knee first will help identify what is normal for that individual.

Figure 5:
Flexion contracture sign. Observe the position of the leg when you ask patients to lie supine and relax their legs. A person who has a flexion contracture in one knee compared with an opposite normal knee will lie with the hip externally rotated because ...
Figure 6:
To evaluate knee extension, the examiner places a hand on top of the thigh to push the back of the knee flat onto the examining table. The other hand is used to lift up on the foot of the patient to evaluate hyperextension. The patient's normal knee has ...

Regaining full knee hyperextension can provide long lasting relief. The mean IKDC subjective score improved significantly between the initial and the 1 month follow-up evaluation, and patients continued to have subjective improvement through the latest evaluation at 1 year after receiving treatment. While rehabilitation sessions can be successful for improving knee extension, the patient must change daily habits to be able to maintain the gains achieved. Educating the patient regarding normal gait and how to stand and properly use the involved extremity is an important factor in maintaining the improvements gained.

CONCLUSION

A rehabilitation program that focuses on increasing range of motion, in particular knee extension, can relieve symptoms and improve function for patients diagnosed with a deconditioned knee. Physical therapy and non-operative treatment should be considered as a primary treatment objective in the treatment of a deconditioned knee regardless of the underlying pathology. As shown in this study, most patients with a deconditioned knee can be treated effectively through non-operative management.

ACKNOWLEDGMENT:

The authors would like to thank The Methodist Health Foundation, Indianapolis, Indiana for their generous and continued contribution to their research.

Footnotes

FINANCIAL DISCLOSURE: K. Donald Shelbourne, MD is a consultant to Kneebourne Therapeutics, Inc.

REFERENCES

1. Andersen RE, Crespo CJ, Ling SM, et al. Prevalence of significant knee pain among older Americans: Results from the Third National Health and Nutrition Examination Survey. J Am Geriatr Soc. 1999;47:1435–8 [PubMed]
2. Knee pain in older adults: the latest musculoskeletal “epidemic.” Ann Rheum Dis. 2001;60:89–90 [PMC free article] [PubMed]
3. Pain in the knee 2005;131–7 Available at http://www.jr2.ox.ac.uk/bandolier/band131/b141-7.html Accessed 12/13/06
4. Jackson JL, O'Malley PG, Kroenke K. Evaluation of acute knee pain in primary care. Ann Intern Med. 2003;139:575–591 [PubMed]
5. National Centers for Health Statistics, Chartbook on trends in the health of Americans. Health. United States: 2006. Available at http://www.cdc.gov/nchs/data/hus/hus06.pdf Accessed 1/5/07
6. Buckwalter JA, Stanish WD, Rosier RN, et al. The increasing need for nonoperative treatment of patients with osteoarthritis. Clin Orthop Related Res. 2001;385:36–45 [PubMed]
7. Divine JG, Hewett TE. Valgus bracing for degenerative knee osteoarthritis. Phys Sportsmed. 2005;33 [PubMed]
8. Lindenfeld TN, Hewett TE, Andriacchi TP. Joint loading with valgus bracing in patients with varus gonarthrosis. Clin Orthop. 1997;344:290–97 [PubMed]
9. Rubin R, Menz HB. Use of laterally wedged custom foot orthoses to reduce pain associated with medial knee osteoarthritis. J Am Podiatric Med Ass. 2005;95:347–352 [PubMed]
10. Deyle GD, Henderson NE, Matekel RL, et al. Effectiveness of manual physical therapy and exercise in osteoarthritis of the knee. A randomized, controlled trial. Ann Intern Med. 2000;132:173–181 [PubMed]
11. Ettinger WH, Jr, Burns R, Messier SP, et al. A randomized trial comparing aerobic exercise and resistance exercise with a health education program in older adults with knee osteoarthritis. The fitness Arthritis and Seniors Trial (FAST). JAMA. 1997;277:25–31 [PubMed]
12. Foley A, Halbert J, Hewitt T, et al. Does hydrotherapy improve strength and physical function in patients with osteoarthritis - a randomized controlled trial comparing a gym based and a hydrotherapy based strengthening programme. Ann Rheum Dis. 2003;62:1162–1167 [PMC free article] [PubMed]
13. Huang MH, Lin YS, Yang RS, et al. A comparison of various therapeutic exercises on the functional status of patients with knee osteoarthritis. Semin Arthritis Rheum. 2003;32:398–406 [PubMed]
14. Thomas KS, Muir KR, Koherty M, et al. Home based exercise programme for knee pain and knee osteoarthritis; randomized controlled trial. BMJ. 2002;325:752. [PMC free article] [PubMed]
15. Ravaud P, Giraudeau B, Logeart I, et al. Management of osteoarthritis (OA) with an unsupervised home based exercise programme and/or patient administered assessment tools. A cluster randomized controlled trial with a 2x2 factorial design. Ann Rheum Dis. 2004;63:703–708 [PMC free article] [PubMed]
16. Thorstensson CA, Roos EM, Petersson IF, et al. Six week high-intensity exercise program for middle-aged patients with knee osteoarthritis: A randomized controlled trial. BMC Musculoskelet Disord. 2005;6:27–29 [PMC free article] [PubMed]
17. Deyle GD, Allison SC, Matekel RL, et al. Physical therapy treatment effectiveness of osteoarthritis of the knee: A randomized comparison of supervised clinical exercise and manual therapy procedures versus a home exercise program. Phys Ther. 2005;85:1301–1317 [PubMed]
18. McCarthy CJ, Mills PM, Pullen R, et al. Supplementation of a home-based exercise programme with a class-based programme for people with osteoarthritis of the knees: A randomized controlled trial and health economic analysis. Health Technol Assess. 2004;8:1–61 [PubMed]
19. Philadelphia panel evidence-based clinical practice guidelines on selected rehabilitation interventions for knee pain. Phys Ther. 2001;81:1675–1700 [PubMed]
20. Kolisek FR, Gilmore KJ, Peterson EK. Slide and flex, tighten, extend (SAFTE): A safe, convenient, effective, and no-cost approach to rehabilitation after total knee arthroplasty. J Arthroplasty. 2000;15:1013–1016 [PubMed]
21. Maloney WJ, Schurman DJ. The effects of implant design on range of motion after total knee arthroplasty. Clin Orthop Related Res. 1992;278:147–152 [PubMed]
22. Parsley BS, Engh GA, Dwyer KA. Preoperative flexion: Does it influence postoperative flexion after posterior-cruciate-retaining total knee arthroplasty? Clin Orthop Related Res. 1992;275:204–210 [PubMed]
23. Ritter MA, Stringer EA. Predeictive range of motion after total knee replacement. Clin Orthop Related Res. 1979;143:115–119 [PubMed]
24. Sultan PG, Most E, Schule S, et al. Optimizing flexion after total knee arthroplasty: Advances in prosthetic design. Clin Orthop Related Res. 2003; 416:167–173 [PubMed]
25. Aglietti P, Buzzi R, De Felice R, et al. Results of surgical treatment of arthorfibrosis after ACL reconstruction. Knee Surg Sports Traumatol Athrosc. 1995;3:83–88 [PubMed]
26. Fisher SE, Shelbourne KD. Arthroscopic treatment of symptomatic extension block complicating anterior cruciate ligament reconstruction. Am J Sports Med. 1993;21:558–564 [PubMed]
27. Millet PJ, Wickiewicz TL, Warren RF. Motion loss after ligament injuries to the knee. Am J Sports Med. 2001;29:664–674 [PubMed]
28. Shelbourne KD, Patel DV, Martini DJ. Classification and management of arthrofibrosis of the knee after anterior cruciate ligament reconstruction. Am J Sports Med. 1996;24:857–862 [PubMed]
29. Shelbourne KD, Johnson GE. Outpatient surgical management of arthrofibrosis after anterior cruciate ligament surgery. Am J Sports Med. 1994;22:192–197 [PubMed]
30. Shelbourne KD, Wilkens JH, Mollabashy A, et al. Arthrofibrosis in acute anterior cruciate ligament reconstruction: The effect of timing of reconstruction and rehabilitation. Am J Sports Med. 1991;19:332–336 [PubMed]
31. Hoppenfeld S. Physical Examination of the Spine and Extremities. Norwalk, Connecticut:Appleton and Lange, 1976
32. Rothstein JM, Roy SH, Wolf SL. The Rehabilitation Specialist's Handbook. 2nd ed.Philadelphia: F.A. Davis Company, 1998
33. DeCarlo MS, Sell KE. Normative data for range of motion and single-leg hop in high school athletes. J Sport Rehabilitation. 1997;6:246–255
34. Rosenberg TD, Paulos LE, Parker RD, et al. The forty-five degree posteroanterior flexion weight bearing radiographs of the knee. J Bone Joint Surg Am. 1988;70:1479–1483 [PubMed]
35. Irrgang JJ, Anderson AF, Boland AL, et al. Development and validation of the International Knee Documentation Committee subjective knee form. Am J Sports Med. 2001;29:600–613 [PubMed]
36. Anderson AF, Irrgang JJ, Kocher MS, et al. The International Knee Documentation Committee subjective knee evaluation form. Normative Data. Am J Sports Med. 2006;34:128–135 [PubMed]
37. Norkin CC, White DJ. Measurement of Joint Motion: A Guide to Goniometry. Third Edition.FA Davis, Co.Philadelphia, 2003
38. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics. 1977;33:159–174 [PubMed]

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