Patellar Tendinopathy

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Description

Patellar tendinopathy is a source of anterior knee pain, characterised by pain localised to the inferior pole of the patella. Pain is aggravated by loading and increased with the demand on the knee extensor musculature, notably in activities that store and release energy in the patellar tendon.

Clinically Relevant Anatomy

Anatomy of the knee joint

The quadriceps muscles are connected to the inferior pole of the patella by the common quadriceps tendon through the sesmoid bone, the patella. The patellar ligament then connects the bottom of the patella to the tibial tuberosity. The force generated from the quadriceps muscles acts through the patellar by acting as a pulley, causing the knee to extend

A healthy tendon is composed mostly of parallel collagen fibers closely packed together (86%). Collagen is predominantly type I. Other components of the tendon matrix are  elastin (2%), proteoglycans (1–5%), and inorganic components (0.2%).

Pathological Process

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. 

Physiological background

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. 

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.    

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.

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.

Outcome Measures

• Pain provocation
• Tendon swelling
• Return to activity

Medical Management

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. NSAIDs have been reported to impede soft tissue healing. Although pain may be reduced, they have a negative effect on tendon repair. In reactive tendinopathy, this may be a preferred effect, as this may inhibit proteins responsible for tendon swelling.

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

Surgery for chronic painful tendons has produced varied outcomes, with 50–80% of athletes able to return to sport at their previous level. Surgery in nonathletic people produced poorer results than in active people. Surgery is considered a reasonable option in those who have failed all conservative interventions.

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

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

Protocol

Protocol as suggested by Malliaris et al. (2015)
Stage	Indication to initiate	Dosage
1. Isometric loading	More than minimal pain during isometric exercise	5 repetitions of 45 seconds, 2 to 3 times per day; progress to 70% maximal voluntary contraction as pain allows
2. Isotonic loading	Minimal pain during isotonic exercise	3 to 4 sets at a load of 15RM, progressing to a load of 6RM, every second day; fatiguing load
3. Energy-storing loading	(A) Adequate strength and consistent with other side (B) Load tolerance with initial-level energy storage exercise (ie, minimal pain during exercise and pain on load tests returning to baseline within 24 h)	Progressively develop volume and then intensity of relevant energy-storage exercise to replicate demands of sport
4. Return to sport	Load tolerance to energy-storage exercise progression that replicates demands of training	Progressively add training drills, then competition, when tolerant to full training

Differential Diagnosis

• Infrapatellar bursitis
• Fat pad impingement
  
• Patellofemoral pain
  
• Plica injuries
  
• Osgood-Schlatter syndrome
• Sinding-Larsen-Johansson syndrome
  

Key Evidence

• Isometric exercise induces analgesia and reduces inhibition in patellar tendinopathy. (Rio 2015)
• Patellar Tendinopathy: Clinical Diagnosis, Load Management, and Advice for Challenging Case Presentations. (Malliaris 2015)
• Physiotherapy management of patellar tendinopathy (jumper's knee). (Rudavsky 2014)
• Achilles and patellar tendinopathy loading programmes. (Malliaris 2013)

Case Studies

• High jumper

Recent Related Research (from Pubmed)

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