Chondromalacia is a disorder of the cartilage at the back of the kneecap. The cartilage, normally shiny and smooth, softens and roughens, and splits may develop in the cartilage.

These changes are similar to the changes that occur to cartilage when osteoarthritis develops. Some people say chondromalacia is part of a spectrum. At the other end of the spectrum is osteoarthritis.

Causes

Chondromalacia can result from many situations where there is excess pressure on the kneecap. 

Direct trauma to the kneecap by a blow or a fall can result in damage to the cartilage or what is known as the chondral surface. Such situations generally only affect one knee.

Activities that cause the kneecap to be pressed against the knee can cause chondromalacia. The greater the level of flexion or bending of the knee, the higher the pressure off the back of the kneecap against the femur and the rest of the knee.

This includes a range of sporting activities or work tasks that require the individual to be kneeling and squatting. It can occur with lunges which may be undertaken as exercise.

Chondromalacia can occur when there is interference with normal patellofemoral movements. The kneecap sits in a groove of the femur bone - or thigh bone. Some people have kneecaps that sit in slightly different positions. The kneecap may be sitting higher than normal, sitting towards the outer aspect of the knee, or might have abnormally angled facets (surfaces) that sit at the back of the kneecap.

Chondromalacia is a common complication for people who have recurrent subluxation or dislocation of the kneecap.

A ridge may be present in the femur in some people, which presses against the back of the kneecap. There may be a fibrous band that becomes thickened and interferes with the normal movement of the kneecap.

Chondromalacia can occur with any disorder that interferes with the normal rhythm of bending the knee. If there is a cartilage tear or inflammation in the lining of the joint, abnormal movement of the knee may occur. This may cause increased pressure on the kneecap as it is forced against the femur.

Muscular abnormalities such as tight hamstrings, or deformities of the foot or leg to be rotated can contribute to chondromalacia.

The clinical picture

Chondromalacia is more common in women than men. It is common in teenage years and is common in certain occupations or sports. Long distance runners and bicycle riders are particularly vulnerable.

People who go up and down stairs repeatedly, particularly carrying loads, are vulnerable. People who sit with their knees in a very flexed position, i.e. bent more than 90°, for long periods of time, are more likely to suffer chondromalacia.

The pain is felt at the front of the knee and is described as a deep-seated ache. It is more noticeable with going up and down stairs, a lot of squatting, or keeping the knees bent for extended periods of time. The pain is not generally present at rest.

For most people this is a condition that occurs in both knees, unless there has been direct trauma to one knee only.

People with chondromalacia also often complain of stiffness, locking, swelling, grinding, catching or a sense of insecurity at the affected knee.

Treatment

People with chondromalacia occasionally have surgery, but the vast majority of cases are managed without an operation.

Key aspects of treatment include avoiding the activities that contribute to the problem and strengthening the quadriceps.

Avoid aggravating activities

Activities that have contributed to the pain, such as squatting, going up and down stairs carrying loads etc., should be avoided to allow the knee to settle.

Exercises

Exercise to strengthen the quadriceps muscle are essential and are the key aspect of conservative management.

Isometric quadriceps exercises should be used. Isometric exercises are squeeze the muscle but don’t actually move the joint.

People are often given non-isometric quadriceps exercises. For example, they may be encouraged to do partial squats and lunges to strengthen the quadriceps. While these exercises are effective at strengthening the quadriceps muscle, they involve pressure on the kneecap and are often counter-productive. Yet they are still commonly recommended for patients with chondromalacia.

A physiotherapist who is knowledgeable in this area should give the person exercises they can do regularly over the day, while standing, while sitting, and while lying down at home. Stretching the hamstrings and hip muscles can also assist.

Medication and taping

Anti-inflammatory medications help some individuals. Taping the knee into a better or more aligned position can also assist some people.

Surgery

Surgery may be necessary if the problem is recurrent. There are a number of different operations that can be performed. A so-called lateral release divides the fibres over the outer aspect of the kneecap, to assist in realigning the kneecap.

The kneecap has a tendon that inserts into the tibial tubercle, just below the knee. An operation to relocate where the patella tendon inserts into the tibial tubercle can be performed.

Shaving of the back of the kneecap is another option, although tends to be done less often and tends to be less successful.

Work activity modifications

Joel is a 36-year-old working on a navy vessel. His duties are varied, but he is up and down stairs all day.  On some of his rostered days of work Joel transfers stores from a hold to the kitchen. He develops pain at the front of both knees, with the right knee the most troublesome. Joel’s roster is six weeks on the ship followed by four weeks off. He rests for the four weeks off work and the problem seems to settle. Yet on his next roster the knee pain returns and is more troublesome.

Joel attends his doctor, who makes a diagnosis of chondromalacia. He is referred to physiotherapy and his knee is taped. His given some quadriceps strengthening exercises to do and encouraged to bike ride. He goes back to his next roster, but the knees are more troublesome.

Joel is then referred to an orthopaedic surgeon. The orthopod suggests that he has been doing the wrong type of exercises. Joel is told not to carry goods under load up and down stairs, to try going up and down stairs sideways (this takes pressure off the kneecap), and he is instructed to stop bike riding and do isometric quadriceps exercises.

At work he avoids carrying loads up and down stairs, continues his isometric quadriceps exercises, and over three months the problem gradually settles down. Joel decides to take up swimming.  He gets into a five day a week swimming routine wearing flippers. This further helps build up his muscular strength in the legs.

After three months Joel is able to gradually get back to his usual job. His soreness doesn’t fully abate but it’s manageable.