Jumpers Knee Explained

Jumper's Knee is the common term for Patella Tendonitis. Typically knee pain comes on gradually if running, jumping and landing activities are practised too much, because the strain on the Patella Tendon becomes too great and microscopic damage develops in the tissue that makes up the tendon. Patella Tendinopathy is usually characterised by degeneration of the tendon, whereas Patella Tendonitis is characterised by inflammation of the Patella Tendon, the latter of which is much less frequent.

The Patellar Tendon is located just below the knee cap (Patella) and is approximately two finger-breadths wide. The tendon is where the Quadriceps (thigh) muscles at the front of the thigh converge and attach to the shin bone. The function of the Patellar Tendon is to transfer the force of the Quadriceps muscles, the contraction of which results in the extension (straightening) of the knee. The Quadriceps muscles are involved in most activities during football, including running and kicking the ball.

The greatest amount of stress is put through the Patella Tendon during jumping and, just as importantly, during landing. During jumping, a player develops an explosive spring by forceful contraction of the Quadriceps muscles, which straighten the knees. Together with the Calf muscles, the Quadriceps push the player up into the air. As the player lands, the Quadriceps help to control the landing by allowing a small amount of knee bending to take place.

If this type of activity is practised too much, the strain on the Patella Tendon becomes too great and there is microscopic damage to the tissue that makes up the tendon. The medical term for this is Patella Tendinopathy. At first, this damage may be too small to cause the player any problems but, if the player continues to over-do jumping activities, the damage will become progressively worse.

Patella tendinopathy is usually characterised by degeneration of the tendon if the tissue is ever examined following surgical removal. This degeneration is a breakdown in the tendon, characterised by small, focal lesions within the tendon without an inflammatory response. The degeneration means that the tendon does not possess its normal tensile strength and is liable to further damage or rupture with continued sporting activity. Apart from sporting overuse, this condition is also associated with ageing. As we get older, our ability to regenerate damaged tissue decreases and the quality of the tendon deteriorates.

Jumpers Knee Signs & Symptoms

Patella Tendinopathy usually comes on gradually. There is pain in the tendon which is worsened by activity. The focal areas of degeneration feel tender to touch. Often the tendon feels very stiff first thing in the morning. The affected tendon may appear thickened in comparison to the unaffected side.

Jumpers Knee Treatment

Patellar Tendinopathy is usually degenerative, and infrequently due to an inflammatory response. Therefore, the use of anti-inflammatory medication (NSAIDs ) is not appropriate. The action of the NSAIDs can actually be counter-productive, as these drugs inhibit the action of naturally occurring chemicals that mediate a healing response, thus dulling the body's ability to regenerate the damaged tissue. Ice Packs can be applied for periods of twenty minutes every couple of hours (never apply ice directly to the skin as it can cause an ice burn).

Early recognition by a doctor or Chartered Physiotherapist helps greatly, because the outcome is better if treatment is initiated early. In minor cases of Patella Tendinopathy, a Patella Tendon Strap can be effective in relieving symptoms by reducing the cross sectional area of the tendon, the pressure applied by the Patella Tendon strap prevents maximal force being transmitted through the tendon. This reduces the strain on the Patella Tendon and helps to alleviate symptoms.

The key to fully recovering from Patellar Tendinopathy is in trying to elicit a healing response without overloading the tendon. This may require rest from sporting activities for up to three months. This is because the collagen tissue, which the body produces to repair the tissue damage, takes three months to lay down and mature. This process may be assisted by treatments that increase the temperature of the tendon, increasing the metabolic activity and thus the healing process in the tendon.

As the tendon is healing, a Chartered Physiotherapist may gently mobilise the soft tissue by providing gentle stress, to help the tendon to adapt and gain tensile strength. Running, jumping and impact activities should be avoided as they can make the knee pain worse. Pool running using a Buoyancy Aid and exercises in water are an excellent method of maintaining cardiovascular fitness without aggravating the injury.

Research has suggested that recovery is optimised by using a programme that uses what is called 'eccentric muscle work'. Eccentric muscle work refers to a muscle that is lengthening while contracting - a contraction that occurs during movements such as landing and decelerating. Maximal tension is generated in the muscle during the eccentric contraction and this causes the tendon to adapt and get stronger.

Eccentric Strengthening Program

In persistent cases of Patella Tendinopathy, an injection of Aprotinin around the tendon helps to prevent further tendon degeneration. Aprotinin is a protein which inhibits the enzyme 'Metalloprotease' that breaks down protein that makes up tendon tissue. This drug is useful as it has been shown that in tendinopathies there is an imbalance between different types of Metalloprotease, and Aprotinin addresses this imbalance. Also, Aprotinin does not have the serious side effects of corticosteroids, and, if necessary, can be injected several times.

Another approach, which is currently being pioneered in Scandinavia, is based on the theory that new blood vessels growing into the diseased tendon are the source of pain. The treatment, which has shown very promising results from the initial studies, is to inject a 'Sclerosant' drug into these blood vessels under the control of an ultrasound scanner which shows the blood vessels. Sclerosant drugs destroy the new blood vessels and hence the proposed source of pain. However, if there is tendon degeneration there may still be a mechanical weakness in the tendon, so there is a lot of research yet to be done on this approach.

In severe cases of Patella Tendinopathy, which have failed to respond to six months of supervised rehabilitation with a chartered physiotherapist, then surgery should be considered. However, this is very much a last resort because the success of surgery, even with the best surgeons, is not 100%.

Surgery involves removing degenerate tendon tissue and trying to restore a tendon to a good level of tensile strength. This means that following surgery the tendon still doesn't have its normal strength and careful rehabilitation is essential. The eccentric program under the supervision of a chartered physiotherapist is indicated. As mentioned earlier, the slow rate of collagen tissue production means that it takes three months to produce new healthy tendon tissue and at least six months before a return to sporting activities can be resumed.

Jumpers Knee Prevention

Training errors should be avoided. The intensity, duration and frequency of training should be carefully monitored and gradually progressed, and sudden increases avoided. Muscle strength and flexibility should be maintained through regular strengthening and stretching sessions. The surface should be appropriate to the sport and it is important to wear the correct footwear. Shock Absorbing Insoles can be helpful, as they reduce the stress on the Patella Tendon during running.

We'd like to thank Professor Nicola Maffulli for his contribution to this article.

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