KNEECAP PAIN SYNDROME PDF Print E-mail

Also known as ‘runner’s knee’, chondromalacia patellae, anterior knee pain, patellofemoral pain syndrome, retropatellar pain, patellar malalignment syndrome, patellar chondropathy, patellar arthralgia, patellalgia and various other names...

What is it?
It is a pain pattern relating to the mechanics of the kneecap: the pain occurs when the knee is moved or held in the bent (flexed) position, or afterwards. It is not the kind of injury where there is specific damage to certain tissues. That is why it has so many names. The condition is recognized by the pattern of pain, after other causes of similar pain are excluded.

Who gets it?
Kneecap pain syndrome is a very common problem which can happen to anyone at any age, although it is considered especially frequent among teenage girls. Non-sporting children and adults are as vulnerable as sports players. Many sports can give rise to the problem, especially distance running, squash, fencing, canoeing and cycling.

How does it happen?
There are three possible causes of kneecap pain syndrome.
1. A direct blow to the kneecap.
2. Activities which use or hold the knee in a bent position.
3. The after-effect of an injury involving other parts of the knee.

In all three situations, the vastus medialis obliquus (VMO) muscle, which controls the knee from the inner side and locks the knee straight, is undermined and becomes weak and/or inefficient. This leads to faulty mechanics in the joint between the kneecap and the main part of the knee (patellofemoral joint): instead of gliding up and down smoothly in its groove on the lower end of the thigh-bone, the kneecap is drawn slightly sideways, towards the outer side of the knee, when you bend and straighten your knee.

Imbalance in the knee’s controlling muscles can be caused all too easily. The many factors which can cause or contribute to kneecap pain syndrome include your normal everyday activities, your posture, sports, weakness or tightness in your thigh muscles, poor foot mechanics, lack of balance in your hips, growth spurts in the young, ageing processes in later years, injuries in any part of the leg and even the shoes you wear. One surprising cause of inhibition to the vastus medialis obliquus muscle is wearing a tubular bandage or knee support for long periods, probably because the pressure restricts the blood flow and interferes with the nerve-muscle co-ordination.

What is the pain like?
The pain can be sudden and sharp, like a stabbing or searing sensation when you put your weight on the leg and bend the knee. It can be severe enough to make you stop in your tracks or limp. More often, the pain is a dull ache, sometimes like a “gnawing” sensation in the front of the knee.

When does the pain occur?
Pain is felt over the front of the knee when the joint is held bent for long periods. The knee also hurts when it bends under the load of your bodyweight, especially going up and down stairs, kneeling or crouching, standing up after sitting for a while, walking or running on hilly or rough ground, or cycling with the saddle too low. The pain may not be immediate, but may come on after activities which put load on to the bent knee, for instance after sitting in the cinema, making a long journey by aeroplane or car, hiking in the hills, or running a marathon. Sometimes there is pain during the night.

What causes the pain?
The pain nerves in the knee are arranged in a very complicated way, so it is difficult to pinpoint exactly why the pain pattern happens as it does. What we do know is that the pain is not specifically related to any damage inside the knee or on the back of the kneecap. There may or may not be damage such as arthritic change or roughening of the bone cartilage. In the young there may be chondromalacia patellae, or softening and pitting in the cartilage surface of the bone. In older age there may be degenerative arthritis (osteoarthritis). If there is identifiable damage, it does not necessarily cause pain: it can be present without hurting. Conversely, there may be severe symptoms typical of the syndrome, without any visible damage to the joint surfaces to explain it.

Diagnosis
Kneecap pain syndrome is usually diagnosed through the history of the symptoms and pain pattern, and the physical assessment which confirms that the vastus medialis obliquus is not functioning properly. One specific test for a sensitive kneecap is ‘Clarke’s sign’: the patient sits or lies on the couch with legs straight and relaxed; the practitioner blocks the top of the kneecap with his/her hand, and asks the patient to tighten the thigh muscles. This causes a stab of pain in cases of kneecap pain syndrome. Personally, I don’t use this test, as the other parts of the assessment can identify the pain pattern perfectly adequately.
Other problems involving the kneecap have to be excluded, especially stress fractures and osteochondritis dissecans, a condition in which flakes of bone cartilage break off and obstruct the kneecap joint.

Skyline X-ray views may be taken to reveal the state of the under-surface of the kneecaps and their position when the knee is fully bent, especially if there is suspicion of damage such as flakes of bone or cartilage from trauma. Other checks, such as blood tests or magnetic resonance imaging, may be used to exclude damage in the knee related to injury or other problems, if the history and examination suggest these are a possibility.

Treatment options
The priority of treatment is to restore efficient function in the vastus medialis obliquus and the muscle groups which co-ordinate with it. One way of achieving this, which I always use, is to apply neuromuscular electrical stimulation to the vastus medialis obliquus, combined with progressive co-ordination exercises .

At first, non-weightbearing and weightbearing exercises for all the thigh muscle groups are performed with the knee held straight. The only exercises involving bending the knee are active and passive stretching for the front-thigh muscles, which are performed lying on the stomach. It is usually necessary to manipulate the kneecap gently to make it more mobile. As vastus medialis obliquus function improves, knee-bending with increasing weight resistance and eventually under bodyweight are added to the programme.

Many practitioners use taping or a small strap to keep the kneecap in better alignment. One treatment programme, known as the McConnell method after its inventor, involves taping the kneecap, and focussing on the vastus medialis obliquus through eccentric muscle work, which makes the muscles lengthen out as they contract. Most often, exercises in this treatment method are done in the standing position, bending and straightening the knee.

Surgery may be needed in cases of severe kneecap pain. One possible operation is the lateral release, in which the binding structures at the outer edge of the kneecap are cut in order to allow the kneecap the freedom to come into better alignment. Sometimes the back of the kneecap is shaved surgically to clear away degenerative material. Following surgery, rehabilitation treatment for the vastus medialis obliquus is vital. Again, I would always use electrical muscle stimulation as the main functional treatment.

In all cases, any secondary contributory factors have to be addressed. If you have poor foot mechanics, you may need special supportive insoles (orthotics). You may need to change your normal shoes: shoes which are unstable can undermine the vastus medialis obliquus by creating too much sideways movement in the leg. Sports shoes which are over-corrective and hold the foot in an excessive degree of pronation or supination will need to be swapped for more flexible footwear. Women’s shoes with very high heels are to be avoided in cases of kneecap pain.

Any kind of imbalance in the leg joints and muscles, for example hip stiffness, hamstring or calf tightness or weakness, hyperextending knee(s), should be corrected, as far as possible, with relevant rehabilitation exercises.

Recovery time
Full recovery is achieved when you have no symptoms on loading the bent knee, for instance when going up and down stairs or crouching down. A simple case of kneecap pain syndrome may be solved within one or two treatment sessions, or the problem can last for months if there is severe limitation and inhibition of vastus medialis obliquus function.

If the problem has been treated surgically, full recovery can be surprisingly slow, often taking longer than recovery from operations which seem more serious, like cartilage removal. After the lateral release operation, rehabilitation usually extends over several weeks, as it is difficult to regain control and co-ordination in the vastus medialis obliquus. If the back of the kneecap has been shaved, the muscle inhibition may be even greater, so the stages of recovery have to be progressed with patience.