Knee
The knee is the largest joint in the body
It is a very exposed joint covered mainly by skin and capsule only, and not covered by muscles or ligaments as most other joints are.
The knee joint is made up by the distal end of the femur and the proximal end of the tibia and the knee cap (patella). All the bone surfaces are covered or lined by articular cartilage forming smooth glistening white surfaces which glide over each other. A small quantity of synovial fluid is present and provides lubrication to the articular surfaces.
Between the ends of the tibia and femur are two ‘floating’ cartilages called menisci. They are often torn and are usually referred to as ‘cartilages’. Several strong ligaments are present which stabilise the knee.
The Knee is Prone to Injury
The knee is subject to unusually large mechanical forces because of its position in the body and this is especially so in athletic or sporting activities in which the knee can be under considerable strain. It follows that it is therefore the most commonly injured joint in the body.
Easily Injured
Because the knee is subject to such large lever arm forces it can easily suffer an acute injury with even the most minor movement such as a simple twist which can result in a tear of the cartilage.
1. Torn Cartilage
A torn cartilage (meniscus) is most often the result of a twisting or rotational movement of the knee joint and can occur in one’s normal daily activities as well as in strenuous athletic or sporting activities.
2. Other Knee Injuries
There are a host of other injuries that can occur in the knee, and which are more often associated with the greater forces involved in athletic activities.
When the knee is damaged in sport injuries, besides meniscal tears, the other common consequence may be a ligament injury such as anterior cruciate ligament rupture or damage to the articular cartilage which covers the ends of the bone.
Microfractures of the underlying bone can occur in a more severe injury.
Dislocation of the knee cap is another serious injury.
Consequences of a Knee Injury
Pain and swelling is the commonest early outcome of a knee injury and is caused either by an outpouring of synovial fluid or by frank bleeding, and both can result in a pressure buildup leading to pain and stiffness. This may be followed by other symptoms such as clicking or locking or giving way and are all the result of a mechanical defect which has occurred. The swelling is always the sign of damage to the knee (an ‘unhappy’ knee).
Knee Arthritis – the final common pathway
Arthritis is a very common condition in the knee but can effect any joint in the body. It is most often the result of wear and tear which comes on as one gets older, but can also result from any other type of acute injury which can trigger it off. It is characterised by pain, swelling and stiffness. Unattended knee injuries will almost certainly result in the development of arthritis, although this condition can also develop spontaneously.
Types of Arthritis
The main type of arthritis is osteoarthritis, which can come on spontaneously, or result from wear and tear.
The other common type of arthritis is caused by rheumatoid disease and is called rheumatoid arthritis and is a much more crippling condition. The cause of the condition is not known, but it is thought to be an auto-immune disease, meaning the body makes antibodies which attack its own tissues which include the muscles, ligaments, and blood vessels and especially the joint. structures.
Treatment of Knee Injuries
1. Physiotherapy
Mobilising the joints and strengthening the associated muscles can usually settle the more minor knee injuries such sprains, strains and muscle tears.
2. Keyhole Surgery
With modern arthroscopic or keyhole surgery, most of the knee injuries can be quickly attended to with minimal down time and few after effects. Recovery with the help of a physiotherapist is usually rapid.
3. Joint Replacement
As arthritis gradually causes more damage to the joint, the stage is reached which no longer responds to keyhole surgery and knee replacement surgery may be necessary. The knee joint is replaced by a metal and plastic prosthesis and the outcome is usually excellent and can dramatically improve the quality of life.
Further Information
The above is an overview of the problems involving the knee and some treatment options. Please refer to the in-depth articles and animations for further information.
Consultant: Divya Prakash