University of Groningen

Patellar tendinopathyZwerver, Johannes

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Chapter 2

Patellar tendinopathy (jumper’s knee):

a common and difficult-to-treat sports injury

J. Zwerver

This chapter is a translated and adapted version of:Patellatendinopathie (‘jumper’s knee’); een veelvoorkomende

en lastig te behandelen sportblessure

Ned Tijdschr Geneeskd. 2008;152:1831-7

16 Chapter 2

Abstract

Patellar tendinopathy is a common and difficult-to-treat overuse injury of the patellar tendon with a very negative impact on the careers of many athletes. It appears to involve a failed healing process in the tendon – not inflammation – and has consequences for the treatment strategy. Rehabilitation programs are based on the principles of load reduction and an eccentric exercise program to improve muscle-tendon function and optimise the kinetic chain. Prolonged rehabilitation is necessary because of slow tendon recovery. Anti-inflammatory treatment is often unsuccessful. Surgery does not guarantee a quick symptom-free return to sport at the original level either. Extracorporeal shockwave therapy, ultrasound-guided sclerosing of new vessels and tendinous and peri-tendinous injections of aprotinin and autologous growth factors seem to be promising new treatment options.

Patellar tendinopathy (jumper’s knee) 17

2

Introduction

Jumper’s knee, also called patellar tendinopathy, is a common condition among both rec-reational and professional athletes,1 and can influence the athlete’s career. In elite basket-ball and volleyball players its prevalence is very high – 32 and 45% respectively.2 It is a chronic injury of the patellar tendon, which is clinically characterised by load-dependent pain at the inferior pole of the patella.1 The high prevalence, the impairment of function and the chronic character of this condition mean that jumper’s knee might have at least as much impact on an athlete’s career as an acute knee injury.2 For some athletes it is even a reason to end their career.3 More than half of athletes with patellar tendinopathy still has some symptoms even 10 years after their career ended.3 General practitioners, physical therapists, sports medicine physicians, sports and reha-bilitation physicians and orthopaedic surgeons frequently see athletes with this typical sports-related knee injury. They use many different treatments, often empirically based, but results are often frustrating for both athlete and doctor or physical therapist.4,5 The poor results can be partly explained by the fact that until recently most treatments were targeted at reducing inflammation in the tendon. In recent years it has been demonstrated that the underlying pathology of patellar tendinopathy, just as in other tendinopathies, is not a tendinitis but rather a failed healing response, tendinosis.6,7 In clinical practice – when no histopathology is available – it is better to speak of patellar tendinopathy. Patel-lar apexitis or patellar tendinitis are also used. This article starts by reviewing the new insights on etiological factors and histopathology of patellar tendinopathy, because they have consequences for the treatment strategy to follow. This is followed by a description of the clinical characteristics and the conservative and surgical treatment of this typical sports injury.

Etiology

The multifactorial etiology of patellar tendinopathy has not yet been completely clari-fied. Men appear to be at a greater risk of getting this condition. Estrogens might protect tendons from getting injured.8 Genetic predisposition seems to be an important factor as well.9

OverloadA disturbed balance between load and loading capacity probably plays an important role. Because this injury is more common among elite than among recreational athletes, a link between training volume and frequency and the prevalence of patellar tendinopathy seems logic.2,10

Reduced loading capacityA reduced loading capacity is also important. If an athlete is less capable of generating or absorbing forces this can result in a wrong jumping and/or landing technique, which gives an increased load on the patellar tendon. Bisseling et al. recently demonstrated

18 Chapter 2

that a stiffer landing strategy, with less motion in knee and ankle, increases the risk for patellar tendinopathy.11 Risk factors associated with this condition are reduced strength of calf, quadriceps and gluteal muscles, inadequate core stability, reduced hamstring and quadriceps flexibility, and hyperpronation of the foot.12,13 Reduced dorsiflexion of the ankle, for example remaining after an ankle distortion which frequently occurs in jump-ing athletes, can play a role.4,14

Pathology

In chronic tendinopathy a failed healing process results in a painful and weakened ten-don, which is then less capable of performing its most important functions, namely ab-sorbing and transducing forces. Repetitive microtrauma caused by overuse give rise to degenerative abnormalities in the tendon like changes in collagen structure and neuro-vascular proliferation.7 There is no inflammatory process. The histopathology is a tendi-nosis, not a tendinitis. Vasculoneural ingrowth might play a role in the concomitant pain in tendinopathies.15

Clinical information

HistoryAthletes with patellar tendinopathy experience pain at the inferior pole of the patella. Pain usually starts insidiously and increases with activities like jumping, sprinting and landing. Symptoms often start after a period of increased training load. In the ini-tial phase symptoms disappear during the warm-up. Athletes tend to keep on going ‘through the pain’ and don’t seek medical help. When they continue to compete at the same level, the pain gradually increases and also remains during sporting activities; eventually, sport performance declines. Finally, there is even pain during daily activities and at rest.To quantify the severity of the patellar tendinopathy during the treatment period one can use the Victorian Institute of Sport Assessment (VISA) score (see Appendix B). For a Dutch translation see Appendix C.16 This questionnaire consisting of eight questions was specifically designed for patellar tendinopathy and evaluates pain, function and sports participation, with a score of 100 reflecting an optimal symptom-free knee. VISA scores of athletes with patellar tendinopathy looking for medical help are around 50–70 points.

Patellar tendinopathy (jumper’s knee) 19

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Physical examinationCircumscript palpation tenderness at the tendon insertion at the inferior pole of the pa-tella is the most characteristic finding during physical examination. The patellar tendon can be thickened. A common finding is atrophy of the quadriceps muscle, especially the M. vastus medialis.As mentioned before, it is important to evaluate potential etiological factors like reduced muscle-tendon function, inappropriate core stability and limited ranges of motion of sev-eral joints. The single leg decline squat is a functional test that loads the patellar tendon and can provoke pain. In this test the athlete, standing on one leg on a decline board at an angle of approximately 25 degrees, gradually flexes the knee (figure 2.1).17 The test can be used to substantiate the diagnosis, but there is no gold standard.

Imaging techniques Although MRI and ultrasound can increase the likelihood of a diagnosis of patellar tendi-nopathy, their value is limited (figures. 2.2 and 2.3).18-22 Patellar tendons of asymptomatic athletes often show sonographic abnormalities, and symptoms and abnormalities can vary during the sports season.23,24 The prognostic and follow-up value of MRI and ultra-sound are also limited because of the poor correlation between clinical symptoms and imaging abnormalities in the tendon.21,25 There may be a correlation between neovascu-larisation (figure 2.3b) on Doppler ultrasound and experienced pain.26,27

Figure 2.1 ‘Single leg decline squat’ test: pain-provoking test to increase the likelihood of patellar tendinopathy.

20 Chapter 2

Figure 2.2. Ultrasound characteristics of patellar tendinopathy: (a) thickened tendon with hypo-echogenic zones and calcifications; (b) colour-Doppler appearance of neovascularisation in the tendon.

femur

tibia

patellaFigure 2.3. MRI of patellar tendinopathy, with increased signal intensity in the proximal part of the tendon; (b) in MRI using a fat-suppression technique.

femur

tibia

patella

Patellar tendinopathy (jumper’s knee) 21

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Conservative treatment

Several, mostly not evidence-based treatment options are used in the management of patellar tendinopathy.4,5 With the current understanding that the underlying pathology in tendinopathies is a tendinosis and not a tendinitis, one should reconsider the treatment strategy. A treatment program for patellar tendinopathy should aim mainly at restor-ing the balance between load and loading capacity and stimulating tendon regeneration rather than reducing the inflammatory process.28

Explanation Athletes with patellar tendinopathy need to get an explanation about the overuse and chronic character of their injury, and should be informed about the fact that a rehabilita-tion program often takes more than three months to achieve full recovery.

Pain reduction Reduction of tendon load can reduce the pain to a tolerable level for the athlete. This does not mean that athletes should completely refrain from tendon-loading activities. Complete rest or even stronger complete immobilisation leads to further weakening of the muscle-tendon unit. It is better to load the tendon very carefully, thereby enabling the athlete to perform pain-free daily activities, participate in a rehabilitation program and adjust sporting activities. Ice packs, taping and bracing (patellar strap) and electrophysical mo-dalities sometimes give some short-term pain relief, but did not evidence a pain-reducing or regenerative effect at longer follow-up.

Exercise therapy to increase loading capacity If strength and endurance of calf, quadriceps and gluteal muscles are weakened one should prescribe strength-training exercises to improve muscle performance. Core stabil-ity should also be optimised. Limitations in joint movements and other causal factors should be corrected. Sport-specific exercises should be included in the final part of the rehabilitation program.

Eccentric exercises Eccentric, slightly painful exercises like the aforementioned single-leg decline squat ap-pear to be effective in the treatment of tendinopathies.6,29-31 During an eccentric contrac-tion the muscle-tendon unit becomes elongated while the muscle contracts, in contrast to isometric and concentric contractions, in which the length respectively stays the same or becomes shorter. For example, during the single-leg decline squat the quadriceps muscle contracts while the patellar tendon-quadriceps unit elongates. Using this eccentric treat-ment strategy VISA scores improved by about 30 points.A practical recommendation for athletes is to perform single-leg decline squats on the in-jured leg once or twice a day, in three series of 15 repetitions for a period of 12 weeks. The precise working mechanism is still unclear but it is likely that these exercises stimulate regeneration in the tendon. The old adage that exercise therapy should be painless is thus open to debate. Some pain during exercise therapy can lead to good treatment results when pain settles within 24 hours and does not increase day by day.32

22 Chapter 2

Extracorporeal shockwave therapyExtracorporeal shockwave therapy seems to be an appropriate additional treatment. Some randomised placebo-controlled studies demonstrate the effectiveness of ESWT on pain and function in patellar tendinopathy.5,33 After ESWT treatment, athletes showed 30 to 40 points higher VISA scores than the control group. The beneficial effect of ESWT might be the result of an analgetic process, destruction of calcifications and stimulation of regeneration processes in the tendon. Unlike ESWT, low-intensity pulsed ultrasound showed no additional benefit over an eccentric training program.34

Anti-inflammatory medication Treatments aimed at reducing inflammation, like the commonly used NSAIDs and injec-tions with corticosteroids, seem to be illogic for degenerative tendons without inflamma-tion. At best, they give short-term pain relief, however their effectiveness in the long run has not been demonstrated. Because of their pain-reducing effect they can mask under-lying problems, resulting in even more extensive tendon abnormalities. Injections with corticosteroids have been controversial in recent decades since they influence collagen synthesis negatively and reduce tendon strength.

Ultrasound guided sclerotherapy An interesting new treatment method is ultrasound-guided sclerosis of the neovessels in the tendon with polidocanol, a well-known sclerosant to treat varices. It is presumed that tendinopathy pain is caused by neurovascular ingrowth in the tendon.35 The effectiveness of this treatment method was recently demonstrated in a randomised clinical trial.36

Figure 2.4. Different types of

muscle contractions:

(a) isometric contraction;

(b) concentric contraction;

(c) eccentric contraction (arrows

indicate direction of movement).

Patellar tendinopathy (jumper’s knee) 23

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Other injection techniques Tendinous and peritendinous injections with aprotinin, a protease inhibitor, or with autol-ogous blood or platelet-rich plasma and growth factors seem to be successful, but further research into the effectiveness of these treatments is necessary.37,38

Surgical treatment

Surgical treatment can be an option when despite a comprehensive and extensive reha-bilitation program conservative treatment fails. Several surgical procedures have been described. Success rates in the literature vary between 60 and 100% and are inversely correlated with methodological quality.39 A recent clinical trial demonstrated that open tenotomy has no advantage over eccentric training.40 Surgery does not guarantee a quick, symptom-free return to sports at the original level. Also, after surgery a prolonged reha-bilitation period according the aforementioned guidelines is necessary.

Conclusion

Patellar tendinopathy is a common overuse injury of the patellar tendon with a very negative impact on the career of an athlete. Up to now no single treatment exists that guarantees a quick and symptom-free return to the original sports level. Therefore, a pro-longed rehabilitation program to restore the balance between load and loading capacity and to promote regeneration of the tendon is the best treatment.

24 Chapter 2

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39. Coleman BD, Khan KM, Kiss ZS, Bartlett J, Young DA, Wark JD (2000). Open and arthroscopic patellar tenotomy for chronic patellar tendinopathy. A retrospective outcome study. Victorian Institute of Sport Tendon Study Group. Am J Sports Med; 28:183-90.

40. Bahr R, Fossan B, Loken S, Engebretsen L (2006). Surgical treatment compared with eccentric training for patellar tendinopathy (Jumper’s Knee). A randomized, controlled trial. J Bone Joint Surg Am; 88:1689-98.