Patella tendonitis

What is Patella Tendonitis?

Patella tendonitis is quite a common problem in which part of the patella tendon, usually the deep part just underneath the knee-cap, becomes damaged and causes localised pain. It is usually seen in sports that involve jumping and indeed is sometimes known as jumpers knee.

What is the Patella Tendon?

The patella tendon is the rope like structure that connects the patella to the tibia (shin bone). It is an extension of the quadriceps muscle of the thigh and as such is a continuation of the tendon of that muscle. The patella (kneecap) is a small bone that develops in the middle of that tendon dividing it into the quadriceps tendon above and the patella tendon below. This arrangement makes for better leverage of that tendon, with the bone holding the tendon further away from the knee joint. The patella also has a smooth undersurface like the rest of the knee joint and can act like a modified pulley, running in a groove in the femur (thigh bone) during knee flexion.

What does this tendon do?

A tendon acts as a rope, which when pulled on straightens the knee. It is the only tendon that acts to straighten the knee and is essential for everyday standing and walking. In a jumping athlete however, it is the essential tendon for transmitting the huge forces that enable the quadriceps to snap the knee straight and create a jump.

How does the tendon become damaged?

In the process of jumping huge forces can be experienced within the tendon substance. In fact, the tendon is strong enough to suspend a small car without rupture. Being this strong the normal tendon rarely ruptures due to sudden overload. Whilst it can rupture this way when the tendon substance is damaged (e.g. in chronic illness such as chronic renal failure and in patients on steroids), this situation is also uncommon.

What happens to the tendon when damage occurs?

The situation that occurs in patella tendonitis is thought to be one of a repetitive partial rupture of the microfibres of the tendon that occurs slowly like a fatigue fracture in metals. In general in the body, gradual fatigue wearing tissues is counter balanced by repair and replacement of that tissue. Overall therefore tissues tend to remain strong enough for everyday activities in any one time the old and damaged portion of a tissue is small and of no significance. Two processes can interfere with this process of renewal:

Excessive breakdown of tissue, which is generally in overuse type of injuries. This is frequently seen in the repetitive jumpers and sports such as basketball. Here the amount of breakdown exceeds the capacity for repair and hence slow deterioration of the tendon ensues.

Decreased healing of the tissues, which is generally an age dependent event. The age in which tendon repair starts to deteriorate may be as young as the early twenties. Everybody is different in this regard, but there is no doubt that some peoples tendons are more resistant to damage and also heal better than others. In other words, some tendons (in some people) are more suited to a higher level of activity than others and hence may have a longer career without significant tendon injury.

How is injury diagnosed?

The commonest place for the tendon to generate is in the deep central aspect immediately below the patella itself. Much less commonly it may occur in the tendon insertion on the tibia and rarely may involve the entire tendon. The pain from the area of tendon damage is generally localised and rarely radiates. Hence the commonest symptom is pain immediately below the kneecap. This is worse when the tendon is stressed (running and jumping etc) and better with prolonged rest. There is often associated inflammation and swelling. The pain is often worse after rather than during activity. The usual pattern is for a gradual onset of pain with use which slowly worsens with time. Initially no modification of activity is required, but gradually as the symptoms worsen, one may have to modify training and ultimately limit sporting activity.

The diagnosis is largely clinical with tenderness of the upper (or effected) part of the patella tendon. Tenderness is generally greater with the knee straight. The best tests to confirm the diagnosis are ultrasound and MRI (magnetic resonance imaging). Ultrasound is more sensitive to operated areas than MRI but when performed by a good radiologist can be relied on almost 100% to confirm or deny the presence of tendonitis. Not only can the lesion be identified but often the degree and extent of fibre damage can be noted.

Does the tendon heal?

Where the damage to the tendon is small and where the potential for healing is high (the young), there may be some healing. This is often repaired with localised scar tissue and providing that this area does not hurt, the result will be a fully functional tendon and few if any symptoms. Where the damage is more extensive, the potential for healing is not great. If rested, the area may become less painful and the function may improve but with a return to higher levels of activity the symptoms return.

How is it treated?

In the early phases a conservative programme is undertaken. This includes adequate rest, modification of training to avoid impact loading, jumping or other stimulatory factors, patella tendon strapping to support the tendon and anti-inflammatory type medication. Physiotherapy and related techniques may have some role to play in strengthening and desensitising the tendon to stress but no techniques have shown the potential to increase tendon healing. Cortisone injections have been used in the past but are very rarely used now due to the concern regarding tendon rupture.

Can surgery cure the problem?

If all of the above treatments fail or the damage to the tendon is bad enough to suggest that it may fail, then surgery may be considered. The surgery for this condition is limited to excision of the damaged area of tendon and possibly any impinging areas of bone on the patella. The problem with this treatment however, is that the outcome is not always as good as we would like and indeed sometimes does not seem to help.

The patella tendon can withstand an excision of about 40% of its fibres and patella tendon rupture following this surgery is rare. Of more concern is that the possibility that the tendon will not be significantly less painful after the procedure. If this occurs then treatment is asked for primary tendonitis with repeated conservative programmes. If ultimately this does not settle down then further excision may be undertaken though results are less satisfactory. The tendon can be made more symptomatic with surgery, but fortunately this is very uncommon.

What is the recovery rate from surgery?

The actual operation is not all that major to perform and can be done as a day case under General Anaesthetic. Usually the surgery is performed through an approximately 5cm transverse incision right over the area of tenderness. Over a 9-12 month period this heals such that in most people it becomes difficult to see. Most people can walk on the knee the same day, although this is limited to short walks around the house for the first few days. Generally by 2 weeks most people have stopped limping and the knee improves thereafter.

By 3 months most people can lightly jog albeit it with some discomfort. A few people will be able to train at that time but that would be considered better than average. Over 6-12 months most gradually get back to sport, but some take as long as 2-3 years to fully settle down. In the majority, the tendon is never clinically symptoms free and most are left with some residual ache which is tolerable, does not stop them playing sport and is not bad enough to consider further treatment. The reason for this protracted recovery is uncertain but it does not seem to relate to how bad the tendon was in the first instance or to how much tendon was removed at surgery.

Overall, surgery for this condition can be regarded as good but rarely does it provide excellent results with a totally asymptomatic knee. When the tendon damage is bad enough however, and conservative treatment has failed there is no other satisfactory alternative to excision of the damaged area.

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