Cartilage damage

Cartilage is an essential part of every joint. In the knee joint the thigh bone, the top of the shin bone and the back of the kneecap are covered with cartilage. Healthy cartilage not only allows the joint surfaces to glide without friction, it also spreads the transfer of force evenly between the parts of the joint. This protects the bone beneath.

Cartilage damage arises either through an injury or as a consequence of chronic overloading, and leads to locally limited damage to the cartilage. This can stay superficial or reach as far as the bone.

As cartilage has only a very limited capacity to heal, damage of this kind generally does not heal without targeted treatment and can grow over time. Cartilage damage is therefore considered a risk factor for developing osteoarthritis.

What happens with cartilage damage?

Definition

Cartilage damage means that the joint cartilage is damaged in one place while the remaining cartilage in the joint is still in good condition. This is to be distinguished from osteoarthritis, in which the cartilage is broken down across the whole joint.

How serious is it?

Cartilage damage can be of different depths. Damage that reaches into the bone beneath is particularly painful – this is known as full-thickness cartilage damage.

Potential for healing

As cartilage tissue has only a very limited capacity to heal, damage of this kind generally does not heal on its own. If the affected areas continue to be loaded, the damage can grow and contribute to the development of osteoarthritis. The aim of non-surgical and surgical measures is therefore to support the healing of the cartilage and encourage the formation of replacement cartilage.

Causes

The causes of cartilage damage are varied: injuries, chronic abnormal loading, metabolic disorders or instability in the knee joint can all play a part. Malalignment that has been present for a longer time – bow legs or knock knees – also increases the load on particular parts of the joint and so encourages cartilage damage. In many cases such damage develops as a consequence of other joint problems, for instance a cruciate ligament tear or an unstable kneecap. Excess weight adds to the load. It is therefore important to identify the cause of the damage as part of the assessment – only then can treatment be successful in the long term.

Diagnostics

The assessment comprises a thorough clinical examination and imaging such as X-ray and magnetic resonance imaging (MRI). Cartilage is not directly visible on X-ray, but the method gives important information about the state of the bone and any signs of osteoarthritis. An X-ray of the whole leg is often taken in addition, in order to identify any malalignment of the axis. MRI allows cartilage damage to be assessed directly, particularly its depth and extent.

Symptoms

The symptoms of cartilage damage can vary considerably. Typical are pain that depends on load – during sport, for example – and swelling of the knee after activity. In advanced cases the symptoms occur at rest or at night as well. The swelling usually arises through irritation of the joint lining, which responds by producing more joint fluid.

Pain

Pain under load is typical

Catching

Uneven surfaces or detached pieces of cartilage can make the joint catch.

Effusion

Irritation of the joint lining makes the joint produce more fluid, and it swells.

The knee joint in detail

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Treatment options for cartilage damage

Non-surgical measures cannot heal the cartilage, but they can relieve pain and swelling markedly. The focus is on building muscle, movement therapy and, where appropriate, injections (with hyaluronic acid or the patient's own blood, for example).

An operation is generally recommended for symptomatic, full-thickness cartilage damage (from a depth of more than 75 %). Depending on the size, depth and position of the damage, different procedures are used. The aim of all surgical treatment is to fill the defective area of cartilage with the patient's own tissue, as close as possible to the original cartilage. This replacement cartilage does not fully restore the original structure, but it can bring a marked improvement in symptoms – often as far as a return to sport.