Patellar Tendinopathy

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Definition/Description

Patellar tendinopathy, also called Jumper’s knee, is a clinical condition of gradually progressive activity-related pain resulting from overuse of the knee.It is a syndrome with micro tears and collagen degeneration in the patellar tendon also due to overuse but non- inflammatory . The term tendinosis should be used as a histopathological and not a symptomatic description. It affects both recreational and elite athletes who run and jump as p.e. in volleyball and basketball. Patellar tendinopathy occurs more frequently in those mature adolescents or adults, ranging from ages 16-40 years. 

• Patellar tendinitis should also be distinguished from Osgood-Schlatter’s disease which is a form of osteochondritis.
• Adolescents growing fast in a short time can be affected by the Sinding-Larsen-Johansson disease.

Clinically Relevant Anatomy

 The knee joint consists three bones, the femur, the tibia, the fibula and also the patella which is a sesamoid. The quadriceps muscles are connected to the patella with a shared tendon and there is also a tendon that connects the bottom of the patella to the tibia, called the patellar tendon. This tendon is extremely strong and allows the quadriceps muscle group to straighten the leg. The patellar tendon is made of tough string-like bands. These bands are surrounded by a vascular tissue lining providing nutrition to the tendon. The patellar tendon is also a ligament.

Epidemiology /Etiology

 These are the most common causes of patellar tendinitis:

• a rapid increase in the frequency of training,
• sudden increase in the intensity of training,
• transition from one training method to another,
• repeated training on a rigid surface,
• improper mechanics during training,
• genetic abnormalities of the knee joint, and/or
• poor base strength of the quadriceps muscles.
  

Physiological background

Acute tendinitis involves an active inflammatory process, often occurring following an injury, which if treated, properly heals in 3-6 weeks. 
Chronic patellar manifest itself after 6 weeks – 3months. These changes include absence of inflammatory cells in the tendon, a tendency toward poor healing, and decreased quality and disorganization of collagen fibers, both of which may lead to decreased tensile strength. Additonally, neovascularization, the growth of new vasculature in areas of poor blood supply, is common in chronic tendinopathy and may contribute to pain perception. The relationship between pain perception and neovasularization is not clearly understood, it is believed that increased levels of the neurotransmitter glutamate may play a role.    

Causes 

There is a higher prevalence noted in sports with high impact ballistic loading to the knee extensors. Microtrauma can occur when the patellar tendon is subjected to extreme forces such as rapid acceleration – decelaration, jumping, and landing.  Drastic changes in frequency and or intensity of training may also lead to overuse training errors. Intrinsic factors such as strength or flexibility may play a role. However the primary causes appear to relate to the extrinsic factors of overuse, improper training surfaces, insufficient foot-wear or inappropriate equipment.  

Characteristics/Clinical Presentation

Pain is the first symptom of patellar tendinitis. The pain usually is located in the section of the patellar tendon . During physical activity, it may feel sharp especially when running or jumping. After the workout it will feel like a dull ache. There is swelling and tenderness in and around the patellar tendon. The knee will often feel ‘tight’ when moved towards flexion.

The purpose of the evaluation is to differently diagnose between condition affecting the patella. We can use the Kennedy Scale to evaluate a chronic patellar tendinopathy  :

1. Phase 1: pain after activity
2. Phase 2: pain at the beginning and after activity
3. Phase 3: pain at the beginning, during and after activity, but the performance is not affected
4. Phase 4: Pain at the beginning, during and after activity, and the performance is affected

Thickness of the tendon may be noted also in all stages. Pain in the patellar tendon may be reproduces with resisted knee extension.
The symptomatic evaluation should include history, age and any recent growth spurts, location of pain, and special tests.

Diagnostic Procedures

The signs and symptoms of patellar tendinitis are fairly easy to detect. The athlete will complain of:

• pain in the area of the tendon,
• the knee will often feel "tight,"
• pain will be experienced early in the workout and after the workout is completed,
• there may be some subtle swelling of the tendon, and
• the athlete may feel that the tendon is "squeaking."

The key physical finding in patellar tendinopathy is tenderness at the inferior pole of the
patella or in the main body of the tendon when the knee is fully extended and the quadriceps relaxed. When the knee is flexed to 90 degrees, thus putting the tendon under tension, tenderness significantly decreases and often disappears altogether.

Differential Diagnosis

Knee pain is a common presenting complaint with many possible causes. Therefore it is important to identify the different disorders. Each have a different patterns that can help to identify the underlying cause more efficiently.

Anterior knee pain

• Patellar subluxation or dislocation
• Tibial apophysitis (Osgood shlatter)
• Jumpers knee (patellar tendonitis)
• Patellofemoral pain syndrome (chondromalacia patellae)

Medial knee pain

• Medial collateral ligament strain
• Medial meniscal tear
• Pes anserine bursitis
• Medial plica syndrome

Lateral knee pain

• Lateral collateral ligament sprain
• Lateral meniscal tear
• Iliotibial band tendonitis

Posterior knee pain

• Popliteal cyst (Baker’s cyst)
• Posterior cruciate ligament injury
  

Examination

Two clinical signs can be performed to assess patellar tendinitis  .

In the “passive extension – flexion sign” the patient lies supine on the examination table. The anterior aspect of the extended knee is palpated to define the point of maximal tenderness.

In the case of patellar tendinitis, tenderness to palpation of the tendon is most often located at the origin of the tendon at the inferior pole of the patella. Once the point of maximal tenderness is identified, the knee is flexed to 90° and pressure is again applied to the tendon.

For the “standing active quadriceps sign”, the patellar tendon is palpated along its course while the patient stands. The point of maximal tenderness identified. The patient is then asked to stand only on the involved extremity with 30° of knee flexion and the tendon was re-palpated.

In both these tests, the patient should note a marked reduction of tenderness to palpation when the knee is flexed or the quadriceps contract, in order to confirm the diagnosis of patellar tendinitis.

Medical Management

There are different types of treatment used in the medical management of tendon disorders.
Unfortunately, few have a strong evidence base.

Non-steroidal anti-inflammatory drugs The use of non-steroidal anti-inflammatory drugs (NSAID’s) in the treatment of tendinopathy remains controversial both in the acute stage and in the chronic stage. NSAID’s do, however, have an analgesic effect possibly independent of the anti-inflammatory action.

Corticosteroid injections Corticosteroid injections are a commonly administered treatment for tendon disorders. All the usual side-effects of corticosteroids are possible (such as skin atrophy, skin hypopigmentation, postinjection flare of symptoms, infection and possible effects from systemic absorption particularly after multiple injections). There is also the possible effect on the mechanical integrity of the
tendons themselves.

Surgical treatment Very good results were achieved. In the chronic stage the lesions are irreversible and constitute permanent intratendinous lesions. It thus seems logical to excise these lesions from their origin at the apex of the patella and entry into the adjacent tendon.

Physical Therapy Management

Advice regarding selective rest should be provided to allow appropriate tendon healing following a period of acute overloading or unaccustomed exercise. There should be a focus on an early return to activities.

Pain relief

Isometrics have been suggested as a possible analgesic exercise where isotonic exercises are not possible due to fatigue and high SIN.

In a small randomised control trial, Rio et al. used a protocol of isometric quadriceps contractions for 5×45 seconds at 70% of participants 1RM.

In a systematic review by Naugle et al. isometric exercise has been found to be superior to aerobic and resistance exercises at reducing pain.

Other therapy adjuncts such as cryotherapy, electrotherapy, patella taping and orthotics have been historically used however there is a lack of evidence to support efficacy. These approaches should not be considered routine and a decision to utilise them would be based on clinician and patient preference.

Rehabilitation

A variety of loading programs have been suggested for the treatment of patella tendinopathy with the main types being:

1. Eccentric loading
   
2. Eccentric-concentric loading
   

Adapted from Malliaras et al. 2013

Program	Exercise type	Sets & reps	Frequency	Progression	Pain
Alfredson	Eccentric	3x15	Twice daily	Load	Enough load to achieve up to moderate pain
Stanish and Curwin/Silbernagel	Eccentric-concentric	3x10-20	Daily	Speed then load, type of exercise	Enough load to be painful in third set
Heavy slow resistance training	Eccentric-concentric	4x6-15	3x/week	6-15RM	Acceptable if was not worse after

Eccentric loading has been the most dominant approach for rehab. Evidence suggests that loading is beneficial in reducing pain and returning function however eccentrics have lower patient subjective satisfaction. This is perhaps due to time commitment and pain required from eccentric programs.

Imaging studies suggest that heavy load training may be more likely to achieve tendon adaptation.

Gym machines such as leg press or knee extension provides control to the amount of loading.

Sports and activity specific

As strength and movement efficacy returns exercises should become specific to the activities the patient would like to return to.Graded approaches are appropriate when returning to activities that are dynamic such as running, jumping and sport.

Suggested rehab protocol

• Selective rest and reduce pain
• Individualised loading program
• Activity specific exercises
  
  

Recent Related Research (from Pubmed)

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