University of Groningen
Patellar tendinopathy
Zwerver, Johannes
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Zwerver, J. (2010). Patellar tendinopathy: Prevalence, ESWT treatment and evaluation Groningen: s.n.
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Chapter 2
Patellar tendinopathy
(jumper’s knee):
a common and difficultto-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 symptomfree return to sport at the original level either. Extracorporeal shockwave
therapy, ultrasound-guided sclerosing of new vessels and tendinous and peritendinous injections of aprotinin and autologous growth factors seem to be
promising new treatment options.
Patellar tendinopathy (jumper’s knee)
17
Introduction
Jumper’s knee, also called patellar tendinopathy, is a common condition among both recreational and professional athletes,1 and can influence the athlete’s career. In elite basketball 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 rehabilitation 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. Patellar 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 clarified. 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
Overload
A 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 capacity
A 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
2
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 jumping athletes, can play a role.4,14
Pathology
In chronic tendinopathy a failed healing process results in a painful and weakened tendon, which is then less capable of performing its most important functions, namely absorbing and transducing forces. Repetitive microtrauma caused by overuse give rise to
degenerative abnormalities in the tendon like changes in collagen structure and neurovascular proliferation.7 There is no inflammatory process. The histopathology is a tendinosis, not a tendinitis. Vasculoneural ingrowth might play a role in the concomitant pain
in tendinopathies.15
Clinical information
History
Athletes 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 initial 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
Figure 2.1 ‘Single leg decline
squat’ test: pain-provoking
test to increase the likelihood of
patellar tendinopathy.
2
Physical examination
Circumscript palpation tenderness at the tendon insertion at the inferior pole of the patella 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 several 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 tendinopathy, 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 ultrasound 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 neovascularisation (figure 2.3b) on Doppler ultrasound and experienced pain.26,27
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 femur
Figure 2.3. MRI of patellar tendinopathy,
with increased signal intensity in the
proximal part of the tendon; (b) in MRI
tibia
using a fat-suppression technique.
patella patella
tibia
Patellar tendinopathy (jumper’s knee)
21
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 restoring 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 rehabilitation 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 muscletendon 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 modalities 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 stability 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 appear to be effective in the treatment of tendinopathies.6,29-31 During an eccentric contraction 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 treatment strategy VISA scores improved by about 30 points.
A practical recommendation for athletes is to perform single-leg decline squats on the injured 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
2
22
Chapter 2
Figure 2.4. Different types of
muscle contractions:
(a) isometric contraction;
(b) concentric contraction;
(c) eccentric contraction (arrows
indicate direction of movement).
Extracorporeal shockwave therapy
Extracorporeal 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 injections with corticosteroids, seem to be illogic for degenerative tendons without inflammation. 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 underlying 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
Patellar tendinopathy (jumper’s knee)
23
Other injection techniques
Tendinous and peritendinous injections with aprotinin, a protease inhibitor, or with autologous 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 rehabilitation 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 rehabilitation 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 prolonged rehabilitation program to restore the balance between load and loading capacity
and to promote regeneration of the tendon is the best treatment.
2
24
Chapter 2
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25
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Chapter 2
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