ACL injury and osteoarthritis: causes, symptoms and treatment

Posted: 29/10/2020

Anterior cruciate ligament, or ACL, injuries are one of the most common types of knee injury and occur particularly in athletes or people who exercise and play sport regularly. ACL injuries can be treated surgically or non-surgically, depending on the patient, but may lead to an increased risk of osteoarthritis in later life. A new study, published in October 2020 in Scientific Reports, suggests that production of a certain protein in the knee joint following ACL injury may indicate an increased risk of osteoarthritis in future, allowing clinicians to better predict and treat this condition at an earlier stage.

What is ACL injury?

The ACL is one of the ligaments in the knee, and helps to move the joint back and forward. It is most commonly injured during running or playing sport: injuries to the ACL are known as ‘sprains’ or ‘tears’. They can range from being mild, where the ligament is just stretched, to severe, where it is completely torn in two.

Patients may become aware of their knee making a popping noise, suddenly giving way, being painful, swelling and/or not moving properly. ACL injury can usually be diagnosed on examination by a doctor, but imaging may be required to ascertain the severity of the injury.

Treatment of ACL injury

If the patient wishes to return to full mobility, ACL injuries tend to require surgery as the ligament cannot repair itself. This can usually be done via arthroscopy (commonly known as ‘keyhole’ surgery), which is less invasive and has a quicker recovery time compared to open surgery. For some elderly or very inactive patients, who do not need to return to great knee mobility, surgery may not be required and they may be able to use a brace and/or have physiotherapy instead if the injury is not very severe.

ACL injury and osteoarthritis

Unfortunately, patients who suffer an ACL injury also have a higher risk of developing arthritis, and in particular osteoarthritis, in the knee as they grow older. Osteoarthritis, also known as ‘wear-and-tear’ arthritis, is common in elderly people, and occurs when the surface of the joint wears away, causing pain, swelling and loss of mobility.

Osteoarthritis cannot be cured but can be treated and prevented from worsening through medications, lifestyle changes such as diet and exercise, and, in some cases, surgery.

The recent study in Scientific Reports has suggested that production of a specific protein that helps lubricate the knee joint may be a predictor of future arthritis in patients with ACL injury. The study was conducted on dogs that had suffered ACL injury but the protein, called lubricin, is present in healthy knee joints in all mammals, including humans. The results may therefore be useful in treating human patients as well, and further studies are taking place to confirm if this is the case.

The study found that levels of lubricin significantly increased in those dogs that had suffered an ACL tear, before any other signs of arthritis were detected. The researchers concluded that increased levels of this protein may therefore be a marker for predicting osteoarthritis earlier, thus allowing patients to seek treatment more promptly and to make the lifestyle changes that could prevent their osteoarthritis from deteriorating.

This study is an encouraging example of how research can aid the development of treatment for common injuries and prevent subsequent and damaging side-effects later on in life.

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