PHYS THER
Vol. 86, No. 3, March 2006, pp. 450-456
Is there evidence to support the use of eccentric strengthening exercises to decrease pain and increase function in patients with patellar tendinopathy?
Alon Rabin
Alon Rabin PT, DPT, MS, CLT is Facility Manager, Accelerated Rehabilitation Center, Farmington Hills, Mich
Submitted April 26, 2005;
Accepted December 8, 2005
| The purpose of "Evidence in Practice" is to illustrate how evidence is gathered and used to guide clinical decision making. This article is not a case report. The examination, evaluation, and intervention sections are purposely abbreviated.
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A 27-year-old man was referred to my physical therapy clinic by an orthopedic surgeon, who had given a diagnosis of right patellar tendinopathy. The patient reported local anterior knee pain in the inferior pole of his right patella. The pain was aggravated by walking, running, and stair climbing but did not prevent him from participating in any recreational activity.
The onset of symptoms was gradual 5 months earlier, and symptoms were aggravated during the 2 months before his visit to my facility. The patient reported that he had increased his running intensity before the onset of his symptoms. The patient had no previous history of right knee disorders but had a reconstruction of his left anterior cruciate ligament 6 years before the clinic visit. No diagnostic studies were performed before the surgeon established the diagnosis.
The patient rated his pain as 1/10 at best and as 5/10 at worst on an 11-point (0–10) numeric pain rating (NPR) scale where 0 represents "no pain" and 10 represents "the worst pain imaginable." Eleven-point NPR scales have been shown to yield reliable measurements of pain in people with a variety of lower-extremity musculoskeletal conditions.1 The patient experienced the pain primarily while running.
The patient scored a 73% on the Knee Outcome Survey-Activities of Daily Living Scale (KOS-ADLS).2 This scale consists of 6 questions assessing common knee symptoms (pain, stiffness, swelling, giving way, weakness, and limping). The scale also includes 8 questions that assess the effect of the knee condition on various activities (walking, going up and down stairs, standing, kneeling, squatting, sitting, and rising from a chair). Lower scores on the KOS-ADLS suggest a greater level of disability. Reliability, validity, and responsiveness for the KOS-ADLS have been established in the assessment of functional limitations that result from a wide variety of pathologies (including patellofemoral pain and knee tendinitis) and impairments of the knee.2 The patient's goal was to be able to resume all recreational activities (particularly running) with no pain or discomfort.
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Physical examination
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The patient's gait was normal, and no effusion or swelling were noted over the right knee. Range of motion was within normal limits, and manual muscle testing, based on Kendall et al,3 revealed mild weakness of the quadriceps femoris and hamstring muscles on the involved side, with a rating of 4/5.
Flexibility testing was performed as described by Magee4 and revealed bilateral hamstring muscle tightness (as measured by active knee extension with the hip bent 90 degrees in the supine position), bilateral iliotibial band tightness (as evidenced by abduction of the hip in the 2-joint hip flexors length test), and right rectus femoris muscle tightness (Ely test). Palpation revealed local tenderness in the inferior pole of the right patella. No other palpable tenderness was elicited over the right knee.
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Evaluation
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The patient appeared to have patellar tendinopathy, an overuse injury that affects athletes in many sports and at all levels of participation but particularly elite jumping athletes.5 The condition is sometimes referred to as "jumper's knee" and is associated with pain just inferior to the patella. The assessment in our patient was based on the location of the symptoms as well as the localized tenderness to palpation over the inferior pole of the patella. No patellar facet tenderness was elicited. Among people who are symptomatic, tenderness to palpation over the attachment of the patella to the patellar tendon is a moderately sensitive test for detecting patellar tendinopathy (positive predictive value 68%).6 Patellar tendinopathy is commonly believed to be resistant to treatment and recurrent in nature.5 Many authors suggest the need to exhaust conservative treatment options before proceeding with surgery.5
In the past, I have come across numerous textbooks7–9 that have advocated the use of eccentric strengthening exercises for the treatment of both patellar and Achilles tendinopathies. At the time I did not know whether these recommendations were based on clinical experience or on scientific evidence. I decided to search the literature for evidence supporting the use of eccentric exercises as an intervention for patellar tendinopathy. I was primarily looking for articles on the effectiveness of eccentric exercises in decreasing pain and improving function in patients with patellar tendinopathy.
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Database used for search
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I decided to use MEDLINE because it contains more than 11 million citations from more than 4,600 biomedical journals. I accessed MEDLINE through OVID Online*
(www.ovid.com), which was available for free at my academic institution. The search process is summarized in Table 1. The search was performed on October 30, 2005.
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First group of keywords
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"Tendinopathy" describes a painful disorder involving a tendon without implying the type of underlying pathology. "Tendinosis" is more recently recognized as a degenerative condition affecting tendons that results in pain. This is in contrast to the previously accepted term "tendonitis," which suggests an underlying inflammatory condition. I also included the term "jumper's knee" as it is commonly used to describe patellar tendinopathy.6 These terms yielded 279, 236, 289, and 91 citations respectively. I decided to combine these keywords using the "OR" operator in order to create one group of all the citations. This can be done by clicking on the Combine icon immediately below the search history table. I then checked the box corresponding to each of the keywords in the search history and selected OR from the dropdown list at the top of the page. This resulted in one group of 828 citations.
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Second group of keywords
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In order to maximize the chances of finding all citations dealing with eccentric exercise, I used the keyword "eccentric" alone. I hoped this would include all citations dealing with eccentric exercises. I also chose the term "exercise" because this is a more general term that may include all exercise interventions, including eccentric exercises. These keywords yielded 5,012 and 129,909 citations respectively.
I decided to combine these keywords using the "OR" operator again. This resulted in 133,937 citations.
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Combining groups of keywords
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I used the Combine feature again, this time to identify all of the citations that dealt with the scope of conditions that I previously selected (ie, tendon disorders) as well as the intervention I was interested in (ie, eccentric, exercise). This time I used the "AND" operator to create one group of citations that included both groups of keywords. A total of 84 citations were found.
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Limits
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Human subjects, English language, articles with abstracts, and the past 10 years.
I decided to limit my search to articles dealing with human subjects, articles in the English language, articles with abstracts, and articles published in the past 10 years. This step limited my search to 56 citations.
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Selection of articles for review
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As I read through my list of citations, I looked for clinical trials on patellar tendinopathy that reported outcome measures such as pain and functional ability. I therefore eliminated literature reviews and clinical commentary articles. I was able to find 6 citations10–15 that seemed to deal with my topic. I checked the box to the left of each of these citations and then clicked on the Selected Citations option in the Citation Manager. The selected citations are listed in the Figure
.
After reading through the abstracts of all 6 citations, I found that these articles dealt with eccentric exercises as a treatment for patellar tendinopathy and reported outcome measures such as pain, function, and return to previous level of activity. I retrieved the articles through the medical library at my academic institution. The 6 articles are discussed below in chronological order.
Panni et al 10: The study is summarized in Table 2.
The researchers classified each participant in the study (N=42) by their stage of patellar tendinopathy, which was based on the scheme of Blazina et al16: - Stage 1: Pain present only after athletic participation, no apparent functional impairment (n=0).
- Stage 2: Pain during and after activity, performance is still at a satisfactory level (n=26).
- Stage 3: Pain is present during and after activity but is more prolonged, progressive difficulties with performing at a satisfactory level (n=16).
Eccentric training may have played a role in the favorable outcome of this study. However, because multiple nonsurgical interventions were used, it is not possible to attribute the results of nonsurgical treatment to eccentric training alone. Moreover, the eccentric exercise protocol was not described in the article. I therefore felt that more solid evidence was needed to justify the use of eccentric exercises in the management of my patient.
Cannell et al 11: The article is summarized in Table 3.
This is a randomized controlled study, with relevant outcome measures. The exercise protocols were described in more detail than in the study by Panni et al.10 However, I could not be certain that the drop squat did not include a concentric component because the authors did not describe how each subject returned to the starting position after each repetition. Similarly, the leg extension exercise may have included an eccentric component on the return to the starting position after each repetition. The outcome of each group may not be attributed strictly to eccentric or concentric loading, but rather to a combination of the two. Finally, although the findings of this investigation suggest that eccentric exercises can reduce pain and help increase function, they were not significantly better than concentric exercises or no exercise at all (because no true control group was used, it could be argued that the outcome of both groups may be attributed to the natural history of the condition). I was hoping to find more solid evidence to justify the use of eccentric exercises in the treatment of patellar tendinopathy.
Stasinopoulos and Stasinopoulos12: The study is summarized in Table 4.
This is another randomized controlled trial. The eccentric exercise was described in detail, and an effort was made to load the quadriceps femoris muscle in a strictly eccentric mode. There were several limitations to this study, however. The study groups were fairly small. In addition, the outcome measure was not previously validated and did not address function. Finally, the eccentric training group also performed flexibility exercises of the quadriceps femoris and hamstring muscles. The outcome of this group, therefore, cannot be attributed to eccentric exercises alone.
Nevertheless, this study suggests that an exercise program consisting of eccentric strengthening and flexibility exercises of the quadriceps femoris muscle results in a superior outcome than other interventions that are commonly used in everyday clinical practice such as ultrasound and deep friction massage. This is the first article I found that suggests that eccentric exercises may yield a better outcome than other interventions.
Purdam et al 13: The article is summarized in Table 5.
Two different exercises were compared in this investigation. Both exercises loaded the knee extensor mechanism in a strictly eccentric mode. The standard one-legged squat appeared fairly similar to the exercise used by Stasinopoulos and Stasinopoulos.12 The authors of this investigation speculated that by performing the same exercise on a declined surface, calf muscle tension would be reduced, allowing a better isolation of the knee extensor mechanism.
The outcome measures of this study were very relevant to my clinical question and the findings of this study suggest that a more isolated eccentric loading of the knee extensor mechanism may yield a better clinical outcome in patients with patellar tendinopathy. The main limitation of this study is the lack of randomization of the subjects to the different intervention groups.
Young et al 14: The article is summarized in Table 6.
This study was a randomized controlled trial that compared the same 2 eccentric exercises that were described by Purdam et al.13 The study used an outcome measurement that was previously validated specifically for patellar tendinopathy and, therefore, was very relevant to my clinical question. The study suggests that (1) both exercises are associated with reduced pain and improved function and (2) a more isolated eccentric load of the knee extensor mechanism may provoke more pain in the short term but is associated with a better likelihood for improved functional outcome in the long term. This study provides more credible evidence for the need to stress the knee extensor mechanism fairly aggressively in order to achieve a better functional outcome.
Visnes et al 15: The article is summarized in Table 7.
The study by Visnes et al made use of a decline squat exercise similar to the exercise that was described by Purdam et al13 and Young et al.14 The study used the same outcome measurement that was used by Young et al,14 which was previously validated specifically for patellar tendinopathy. This is the first study that found no benefit to the use of eccentric exercises in the treatment of patellar tendinopathy. Although this was a randomized controlled trial with a true (no intervention) control group, several confounding factors may have influenced its outcome. First, participants in this study did not independently seek medical intervention for their patellar tendinopathy. Rather, it was the investigators who approached the participants' teams seeking possible study subjects. The study population, therefore, may not truly represent the patient population likely to be seen in everyday physical therapist practice. Second, the intervention was applied while the participants were active with their respective teams during in-season volleyball games and practices. The authors of the study acknowledge that this is a possible explanation for the failure of the protocol to yield positive results. The load on the tendons of the participants may have been too great.
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Clinical decision related to the treatment approach of my patient
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Five of the 6 articles I retrieved suggested that reduction of pain and return to previous level of activity, which were my patient's primary goals, were associated with the use of eccentric exercises. Each of these studies either had methodological shortcomings10,12–14 or did not find eccentric strengthening to be more beneficial than other forms of exercises.11 Nevertheless, when viewed as a group, I thought these articles justified a trial use of eccentric exercises in the management of my patient's condition. Moreover, the one study15 that did not find eccentric exercises to be beneficial dealt with elite volleyball players during in-season participation. This population was quite different from my patient.
I explained the treatment rationale to my patient and emphasized that the intervention was probably going to cause a certain amount of discomfort. I also explained to my patient that this discomfort should not be disabling. Discomfort associated with the performance of eccentric strengthening exercises is a common side effect. Eccentric loading places the highest tensile loads through the tendon and, therefore, is associated with pain.17 In the majority of the studies that I reviewed, subjects were instructed to perform the exercises through pain (but not through pain that is disabling, however).12–15 In fact, loads were increased once pain was no longer felt.
My patient was willing to try this approach. I therefore prescribed an exercise protocol consisting of exercises that stressed the knee extensor mechanism in an eccentric mode only. The patient was encouraged to perform these exercises despite feeling a moderate amount of pain but to discontinue if the pain became disabling.
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Follow-up
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Week 1: After 1 week of therapy, the patient reported a reduction of his pain to 4/10 at worst on the NPR scale. The patient did report knee pain over the patellar tendon while performing his exercises. This pain did not exceed an intensity of 5/10 and did not last very long after exercise.
Week 3: The patient reported a reduction of his pain to 2/10 at worst on the NPR scale. The patient scored his KOS-ADLS at 80%.
Week 5: The patient reported his pain level to be 4/10 at worst on the NPR scale, and the KOS-ADLS was scored at 76%.
Week 10: The patient reported his worst pain to be 2/10 on the NPR scale and scored his KOS-ADLS at 83%. This was in comparison to 5/10 on the NPR scale and 73% on the KOS-ADLS before initiating treatment.
At this time formal physical therapy was discontinued because the patient's third-party provider would not cover additional sessions. I instructed the patient to continue his current exercise regimen for 1 or 2 additional months. The patient was discharged and was asked to call if he experienced any aggravation of his symptoms.
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Footnotes
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The author would like to acknowledge Anthony Delitto, PT, PhD, FAPTA, for providing guidance and consultation throughout this project.
* Ovid Technologies, 100 River Edge Dr, Norwood, MA 02062. 
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References
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- Stratford PW, Spadoni G. The reliability, consistency and clinical application of a numeric pain rating scale. Physiother Can 2001;53:88–91, 114.
- Irrgang JJ, Snyder-Mackler L, Wainner RS, et al. Development of a patient-reported measure of function of the knee. J Bone Joint Surg Am 1998;80:1132–1145.[Abstract/Free Full Text]
- Kendall FP, McCreary EK, Provance PG. Muscles: Testing and Function, With Posture and Pain 4th ed. Baltimore, Md: Williams & Wilkins; 1993.
- Magee DJ. Orthopedic Physical Assessment 3rd ed. Philadelphia, Pa: WB Saunders Co; 1997.
- Cook JL, Khan KM. What is the most appropriate treatment for patellar tendinopathy? Br J Sports Med 2001;35:291–294.[Free Full Text]
- Cook JL, Khan KM, Kiss ZS, et al; Victorian Institute of Sport Tendon Study Group. Reproducibility and clinical utility of tendon palpation to detect patellar tendinopathy in young basketball players. Br J Sports Med 2001;35:65–69.[Abstract/Free Full Text]
- Greenfield BH. Rehabilitation of the Knee: A Problem-Solving Approach Philadelphia, Pa: FA Davis Co; 1993.
- Albert A. Eccentric Muscle Training in Sports and Orthopaedics 2nd ed. New York, NY: Churchill Livingstone Inc; 1995.
- Brotzman BS. Clinical Orthopaedic Rehabilitation Philadelphia, Pa: Mosby; 1996.
- Panni AS, Tartarone M, Maffulli N. Patellar tendinopathy in athletes: outcome of nonoperative and operative management. Am J Sports Med 2000;28:392–397.[Abstract/Free Full Text]
- Cannell LJ, Taunton JE, Clement DB, et al. A randomised clinical trial of the efficacy of drop squats or leg extension/leg curl exercises to treat clinically diagnosed jumper's knee in athletes: pilot study. Br J Sports Med 2001;35:60–64.[Abstract/Free Full Text]
- Stasinopoulos D, Stasinopoulos I. Comparison of effects of exercise programme, pulsed ultrasound and transverse friction in the treatment of chronic patellar tendinopathy. Clin Rehabil 2004;18:347–352.[Abstract/Free Full Text]
- Purdam CR, Jonsson P, Alfredson H, et al. A pilot study of the eccentric decline squat in the management of painful chronic patellar tendinopathy. Br J Sports Med 2004;38:395–397.[Abstract/Free Full Text]
- Young MA, Cook JL, Purdam CR, et al. Eccentric decline squat protocol offers superior results at 12 months compared with traditional eccentric protocol for patellar tendinopathy in volleyball players. Br J Sports Med 2005;39:102–105.[Abstract/Free Full Text]
- Visnes H, Hoksrud A, Cook J, Bahr R. No effect of eccentric training on jumper's knee in volleyball players during the competitive season: a randomized clinical trial. Clin J Sport Med 2005;15:227–234.[Medline]
- Blazina ME, Kerlan RK, Jobe FW, et al. Jumper's knee. Orthop Clin North Am 1973;4:665–678.[Medline]
- Fyfe I, Stanish WD. The use of eccentric training and stretching in the treatment and prevention of tendon injuries. Clin Sports Med 1992;11:601–624.[ISI][Medline]
Copyright © 2006 by the American Physical Therapy Association.
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