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​How a knee injury can increase your risk of Osteoarthritis

20th September 2018

According to the NHS, osteoarthritis affects about 8 million people in the UK. While in many cases, the condition develops as a result of the slow degeneration of joints brought on by ageing, your susceptibility for developing osteoarthritis in the knee may increase if you have previously suffered an injury to the joint.

What is osteoarthritis?

Osteoarthritis is a subcategory of arthritis and is characterised by the wearing away of the cartilage lining around a joint, which leads to the joint being able to move less smoothly. As a result, the tendons and ligaments around the joint have to work harder to maintain mobility, leading to swelling, stiffness and pain. As the condition progresses, the bones of the joint may start to rub against each other (leading to the formation of bony projections known as osteophytes) and may become misaligned (leading to visible deformity of the joint area).

Osteoarthritis in the knee

Generally, the condition develops in older adults as a result of wear and tear, and it’s most common in women and people who have a family history of the condition. In addition, osteoarthritis can develop following an injury or as a result of other joint conditions, such as rheumatoid arthritis.

One of the most common places to develop osteoarthritis is the knee, and this can be exacerbated if the knee suffers a major injury. The knee is a complex area of the body where a number of ligaments, bones, muscles and tendons interact to provide movement and bear weight. In addition, unlike many other joints, the knee is only really designed to move forwards and backwards, so is more prone to injuries from impacts and torsion.

Post-traumatic osteoarthritis can develop in the knee in three main cases:

Repetitive stress of the knee joint (usually as a result of hard physical activity, such as mining and farming)

Trauma to the knee joint (usually as a result of an impact, tear or breakage from playing sports, or being involved in an accident)

Previous surgery on the knee joint

The two most common injuries that can lead to osteoarthritis are the tearing of the anterior cruciate ligament (ACL) or the posterior cruciate ligament (PCL), and the tearing of the meniscus cartilage.

ACL and PCL tears

The ACL and the PCL are two of the most important components of the knee joint: they are the ligaments that connect the thigh bone to the shin bone and help stabilise the knee. The ACL and PCL provide forward and backward motion for the knee, so injuries to these ligaments often occur as a result of sudden changes in speed or direction, such as in football or basketball, or a strong impact or wrong landing, such as in gymnastics, or martial arts.

ACL and PCL injuries are usually easy to spot, as they result in sudden pain and swelling, an inability to bear weight, and the joint can feel loose. In addition, it is common to hear a popping or snapping sound at the time of the injury.

An ACL or PCL injury means that the affected knee is less able to bear weight, and the forward and backward action of the knee joint becomes less smooth. Both these factors contribute to increased risk of developing osteoarthritis in the long-term, especially since the recovery period is very long in the case of such injuries. Even with corrective surgery, those with ACL injuries are at a higher risk of developing osteoarthritis. According to one study, as many as 80% of people with an ACL injury went on to develop osteoarthritis within 5-15 years following the injury. This high incidence is due to the fact that ACL tears rarely occur in isolation (they are frequently accompanied by damage to the meniscus and other areas of the knee), and the key role that the ACL plays in the makeup of the knee means that such an injury compromises knee function in the long term.

Meniscal tears

The meniscus is a layer of cartilage that sits between the shin and thigh bones, preventing the bones from rubbing against each other, and facilitating movement by allowing the two leg bones to slide smoothly within the knee joint. It also acts as a shock absorber when walking and helps to bear weight by distributing stress evenly down the knee. The meniscus is comprised of two parts - one lateral and one medial.

Damage to this area commonly occurs as a result of activities that put increased pressure or rotation on the knee joint, such as fast-paced sports like football and basketball, as well as dancing and gymnastics. However, a larger segment of the population is prone to meniscal tears in comparison to ACL tears, as injury to the cartilage can also happen simply as a result of getting up too quickly from a sitting or squatting position, and it can therefore affect children and the elderly, in addition to those who play sports or engage in other physically demanding activity.

The danger with meniscus tears is that they may not be picked up on until some time after the injury has occurred, as it is possible to maintain knee function, albeit with some pain and stiffness, despite the injury, and therefore dismiss it as a less severe injury. However, it is important to obtain an accurate diagnosis as early as possible, as a damaged meniscus can lead to the development of osteoarthritis in the long term. A torn meniscus affects the weight-bearing ability of the knee, so the other ligaments and tendons need to compensate, placing extra stress on the knee joint. In addition, the ease of movement of the shin and thigh bones against each other can become less smooth, causing them to rub against each other. Both of these conditions contribute to the development of osteoarthritis.

Treatment of osteoarthritis

Unfortunately, there is no real cure for osteoarthritis, so minimising the risk of injury is key. In order to decrease the chance of osteoarthritis developing, it is important to maintain a healthy weight, as being overweight places extra stress on the knee. In addition, engaging in regular and safe physical activity will help strengthen the muscles and ligaments of the knee.

If any injury has occurred, there are measures that can be implemented in order to avoid further degeneration of the joint. Treatments to ease symptoms include surgical and non-surgical routes. Generally, surgery is only offered to those for whom non-surgical options have not been successful, but each case will be assessed individually by a GP. Common non-surgical interventions include lifestyle changes to improve fitness and maintain a healthy weight, in order to ease unnecessary stress on joints, physiotherapy, and wearing specialised footwear and braces to help distribute weight more evenly. Meanwhile, surgical interventions range from injections through to knee replacement therapies.

Despite the fact that osteoarthritis is a long-term degenerative condition, with the right treatment plan, it is possible to slow down or even reverse the condition to some extent. Therefore, if you have suffered an injury to the knee, it is very important to obtain a full diagnosis and to explore treatment options as early as possible, so that the injury can be properly managed to decrease the likelihood of osteoarthritis developing.

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