Key messages
— The evidence for using strengthening exercises to treat patellar tendinopathy (pain at the front of the knee involving the tendon) is very uncertain, making it difficult to draw firm conclusions.
— For athletes, we are very uncertain whether exercise reduces pain compared to no treatment. Strengthening exercises may make little or no difference to function compared to no treatment, and little or no difference to function and pain compared to glucocorticoid injections (anti-inflammatory medications).
— It is unclear if these exercises are better than surgery for reducing pain or improving function. Athletes reported similar treatment success and return to sport with strengthening exercises and surgery.
What is patellar tendinopathy?
People with patellar tendinopathy (jumper's knee) usually have pain and tenderness upon pressing the tendon at the front of the knee (connects muscles to bones). This frequently affects people in activities requiring repetitive jumping, braking, kicking, or running. Patellar tendinopathy can cause disability in both athletes and non-athletes, significantly impacting athletic performance and career longevity.
How is patellar tendinopathy treated?
One of the main treatments for patellar tendinopathy is exercise, especially strengthening exercises. Other options include anti-inflammatory medications (such as glucocorticoid injections) and, in some cases, surgery. Additional treatments that have been used include platelet-rich plasma injections (a concentrated component of the blood injected into the knee), ultrasound therapy (which uses sound waves to reduce pain and support healing), laser therapy (which uses focused light to decrease pain and swelling, and speed up healing), and shockwave therapy (which uses high-energy sound waves to stimulate healing and reduce pain).
What did we do?
We searched for studies comparing exercises with other treatments (such as no treatment, anti-inflammatory medicines (for example, glucocorticoid injection), and surgery) in people with patellar tendinopathy. We collected data on pain, function, treatment success, quality of life, return to sport, and unwanted effects, and assessed how confident we were in the results.
What did we find?
We found seven studies published between 1989 and 2022, and reported in English. Two studies were from Norway, and one each from Denmark, Germany, Greece, Poland, and the US.
Key findings
Pain (measured between 0 and 100, lower scores mean less pain) at end of treatment.
We are very uncertain whether exercise reduces pain compared to no treatment.
– People in the exercise group rated their pain as 27 points.
– People in the no-treatment group rated their pain as 62 points.
Exercise may make little or no difference to pain compared to glucocorticoid injection.
– People in the exercise group rated their pain as 24 points.
– People in the glucocorticoid injection group rated their pain as 18 points.
We are very uncertain whether exercise reduces pain compared to surgery.
– People in the exercise group rated their pain as 13 points.
– People in the surgery group rated their pain as 17 points.
Function (measured between 0 and 100, lower scores mean better function) at end of treatment.
Exercise may make little or no difference to function compared to no treatment.
– People in the exercise group rated their knee function as 72 points.
– People in the no-treatment group rated their knee function as 65 points.
Exercise may make little or no difference to function compared to glucocorticoid injection.
– People in the exercise group rated their knee function as 76 points.
– People in the glucocorticoid injection group rated their knee function as 82 points.
We are very uncertain whether exercise reduces function compared to surgery.
– People in the exercise group rated their knee function as 52 points.
– People in the surgery group rated their knee function as 45 points.
Treatment success (measured from −5 to +5, +5 means maximum improvement) at the end of treatment.
Exercise may make little or no difference to treatment success compared to surgery.
– People in the exercise group rated their success as 1.7 points.
– People in the surgery group rated their success as 0.2 points.
Return to sport rate measured at 12 months.
Exercise may make little or no difference to the rate of return to sport compared to surgery.
– 85 out of 100 people returned to sport after exercise treatment.
– 86 out of 100 people returned to sport after surgery.
What are the limitations of the evidence?
The effectiveness of strengthening exercises for athletes is uncertain. There were few studies of varying quality, with a small number of people. All studies only included athletes, so the results may not apply to people who are not athletes. No studies reported unwanted effects.
How up to date is this evidence?
The evidence is up to date to 5 September 2023.
We are very uncertain whether strengthening exercise reduces pain compared to no treatment. Strengthening exercise may make little or no difference to function compared to no treatment and to function or pain compared to glucocorticoid injection. Compared to surgery, we are very uncertain whether strengthening exercise reduces pain or improves function, and it may make little or no difference to treatment success and the proportion of athletes returning to sport. No trials measured adverse events. All trials analyzed in this review included participants who were athletes, limiting the findings to athletes rather than the general public.
Patellar tendinopathy is a prevalent condition that commonly affects the tendon's origin, causing pain at the front of the knee. The main treatment for patellar tendinopathy involves different types of exercise (e.g. strengthening and stretching). The most common method of strengthening exercise is eccentric (lengthening) muscle loading. Strengthening exercises can be land-based or water-based, weight-bearing or non-weight-bearing, or both. Other treatments include surgery and glucocorticoid injections.
To evaluate the benefits and harms of exercise for the treatment of patellar tendinopathy.
We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and two trials registers to 5 September 2023, with no restrictions by language.
We included randomized controlled trials of strengthening exercise interventions compared to placebo or sham intervention; no treatment, usual care, or minimal intervention; or other active intervention. Strengthening exercises include concentric, eccentric, eccentric-concentric, and isometric exercises designed to enhance the strength and power of muscles.
Two review authors independently selected studies for inclusion, extracted data, and assessed risk of bias and certainty of evidence using GRADE. Major outcomes included pain, function, participant-reported global assessment of treatment success, quality of life, return to sport, proportion of participants with adverse events, and proportion of participant withdrawals.
We included seven trials (211 participants with chronic patellar tendinopathy) comparing strengthening exercises with no treatment (3 trials, 93 participants), glucocorticoid injection (1 trial, 38 participants), surgery (1 trial, 40 participants), stretching exercise (1 trial, 15 participants), or pulsed ultrasound and transverse friction (1 trial, 30 participants). All trials included athletes (88% males, mean age 26 years) with a mean duration of symptoms of 41.6 months. Most trials were susceptible to bias, particularly selection bias/random sequence (57.1%), selection bias/allocation concealment (42.8%), detection bias (28.5%), attrition bias (71.4%), and selective reporting biases (28.5%). Given the nature of the intervention, neither participants nor investigators were blinded to group allocation in any trials (performance bias).
We did not find any studies that compared exercise with placebo or sham intervention.
Strengthening exercise versus no treatment
We are very uncertain whether strengthening exercise reduces pain compared to no treatment. Mean pain with no treatment was 62.00 points on a 0 to 100 scale (0 = no pain) compared to 27.06 points with exercise (mean difference (MD) 34.94 points better, 95% confidence interval (CI) 20.94 better to 48.94 better; 1 study, 39 participants; very low-certainty evidence (downgraded twice for imprecision and once for bias)). Strengthening exercise may make little or no difference to function compared to no treatment at the end of treatment. Mean function with no treatment was 65.00 points on a 0 to 100 scale (100 = best function) compared to 72.04 points with exercise (MD 7.04 points better, 95% CI 6.94 points worse to 21.02 points better; 2 studies, 95 participants; low-certainty evidence (downgraded once for imprecision and once for bias)).
The studies reported none of the other outcomes.
Strengthening exercise versus glucocorticoid injection
Strengthening exercise may make little or no difference to pain compared to glucocorticoid injection at the end of treatment. Mean pain with glucocorticoid injection was 18.00 points on a 0 to 100 scale (0 = no pain) compared to 24.04 points with exercise (MD 6.04 points worse, 95% CI 8.19 better to 20.26 better; 1 trial, 38 participants; low-certainty evidence (downgraded twice for imprecision)).
Strengthening exercise may make little or no difference to function compared to glucocorticoid injection at the end of treatment. Mean function with no treatment was 82.00 points on a 0 to 100 scale (100 = best function) compared to 76.25 points with exercise (MD 5.75 points worse, 95% CI 17.41 worse to 5.93 better; 1 trial, 38 participants; low-certainty evidence (downgraded twice for imprecision)).
The trial reported none of the other outcomes.
Strengthening exercise versus surgery
We are very uncertain whether strengthening exercise reduces pain compared to surgery at 12-month follow-up. Mean pain with surgery was 13.00 points on a 0 to 100 scale (0 = no pain) compared to 17.00 points with exercise (MD 4.00 points worse, 95% CI 4.06 better to 12.06 worse; 1 trial, 40 participants; very low-certainty evidence).
We are very uncertain whether strengthening exercise improves function compared to surgery. Mean function in the surgery group at the end of treatment was 45.10 points on a 0 to 100 scale (100 = best function) compared to 52.4 points in the exercise group (MD 7.30 points better, 95% CI 5.02 worse to 19.62 better; 1 trial, 40 participants; very low-certainty evidence (downgraded once for bias and twice for serious imprecision)).
Strengthening exercise may make little or no difference to treatment success compared to surgery at the end of treatment. The mean global assessment of treatment success with surgery was 0.2 points on a −5 to +5 scale (+5 maximum was improvement) compared to 1.76 points with exercise (MD 1.56 points better, 95% CI 0.52 worse to 3.64 better; 1 trial, 40 participants; low-certainty evidence (downgraded once for bias and once for imprecision)).
Strengthening exercise may make little or no difference to the rate of participants who returned fully or partially to sport when compared to surgery at 12-month follow-up. The return to sport rate with surgery was 86% compared to 85% with exercise (risk ratio 1.02, 95% CI 0.78 to 1.34; 1 trial, 40 participants; low-certainty evidence (downgraded once for bias and once for imprecision)).
The trial reported none of the other outcomes.