Knee Arthritis

The pain in the knee tends to be aggravated by activity and, as the condition progresses, the affected individual finds that he, or she, experiences increasing difficulty in walking. This is not only due to the discomfort which this causes in the joint but because the knee becomes stiff. The knee begins to swell at times, this being due to two factors; enlargement of the bones about the knee and the development of an effusion i.e. ‘water on the knee’. In some cases the knee develops an angular deformity and people with the problem commonly develop ‘bow legs’.

X-rays of the knee, in the advanced case, show the typical signs of arthritis in the joint, specifically narrowing of the radiological ‘joint space’ with some whitening (sclerosis) of the adjacent bones.

 

When the condition is far advanced the cause for the pain in the knee becomes very obvious during the clinical examination and on examining the x-rays. However, in the early stages, it may not be easy to identify arthritis from the many other causes for pain in the knee and further investigations may be necessary before a diagnosis may be made with confidence.

A radionucleotide scan of the knee will demonstrate inflammation within the knee but this, nevertheless, is a relatively non-specific investigation.

A Magnetic Resonance Imaging scan of the knee will demonstrate many abnormalities within the knee and may serve to differentiate arthritis from the other common causes for pain in this joint.

One of the most satisfactory investigations is to look inside the joint itself. This method is called ‘arthroscopy’ and consists of inserting a small telescope into the knee. This allows the surgeon to directly visualise any damage or other abnormality which may be present.

The aim of treatment of arthritis of the knee is to relieve the pain which is present and to maintain function, specifically walking. In many instances various non-surgical measures can help.

• Analgesic tablets, specifically non-steroidal anti-inflammatory tablets can ease the pain.

• The use of a walking aid such as a walking stick to reduce the pressure through the joint is usually of some assistance.

• Reducing body mass also serves to reduce the pressure through the knee and thus reduce the pain on walking.

• If an adequate Orthotic service is available various wedges or inserts into the shoes can sometimes bring about a marked reduction pain by redistributing the forces which pass through the joint.

• Sometimes the weight of the bedclothes cause pain in the knee while trying to sleep. In this case a cage over the leg makes sleeping more comfortable.

• It is important to maintain the movement of the knee. Gentle exercises are advised and, in this respect, the assistance of a Physiotherapist is of great assistance.

• If the condition continues to deteriorate despite using the measures outlined above, some surgical procedure may be unavoidable.

Arthroscopy – arthroscopic assessment of the knee, in itself, has been shown to be of assistance in many people. The procedure removes many of the inflammatory products which accumulate in the joint as the result of the arthritis and, in doing so, reduces the pain. It is also often possible to deal with some of the factors within the joint which have contributed to the arthritis and, in this way, reduce the discomfort which is being experienced.

Osteotomies – the knee is especially susceptible to the adverse effects of a mal-alignment of the leg, whether the deformity is due to a previous injury or to some other cause. The arthritis in this case is due to an abnormal distribution of stress across the knee while standing and walking. Cutting and reshaping the bones of the leg will allow correction of the deformity and, by correcting the distribution of stress across the knee will relieve the pain in the joint.

Total knee arthroplasty – the procedures described above are often effective when the arthritis is localised to a small area of the knee. In cases where the arthritis is widespread and there is significant destruction of the articular cartilage of the joint some form of artificial joint may be the only way to obtain relief. Essentially there are two types of artificial knee joints which are inserted; a unicondylar knee arthroplasty, where only one side of the knee joint is replaced by a prosthesis; and a total knee joint, in which case both sides of the knee joint are replaced.

The total knee arthroplasty is designed to emulate the action and function of the normal knee joint. In this operation the knee joint is opened through an anterior incision to expose the damaged articular cartilage on the surfaces of the femur and tibia. The cartilaginous menisci between them are removed. The articular surfaces of the femur and tibia are trimmed to size, using jigs specific for the specific design of prosthesis which is being used. The artificial components are inserted to replace the excised surfaces. These components are bonded to the bone either by orthopaedic ‘cement’ or by a special coating which encourages bone to grow into it. To enhance the articulation between the components a shaped plate of dense polyethylene is placed between them. After surgery the knee may swell for a while and has a tendency to become stiff. In order to regain movement of the leg and derive maximum benefit from the new prosthesis, it is important to begin movement of the joint as soon as possible after the operation. Weight bearing is usually encouraged as soon after the operation as possible.

Again there are the caveats with respect to these operations:

The operations themselves are not without their hazards. Various complications can ensue which include:

• Continuing pain
• infection of the knee
• deep vein thrombosis
• pulmonary embolism
• damage to nerves or blood vessels
• loosening of the prosthesis
• malalignment of implants
• in the case of an osteotomy, non-union of the bony fragments.

The artificial knees have a finite life and may have to be revised at some stage. It may, however, be many years before this is necessary.

The risk, however, of developing any one of these complications is relatively low and there are many hundreds of thousands of people who will attest to the benefits to be obtained from these procedures by way of reduced pain and greater freedom of movement.