Meniscus injury

The menisci (plural of meniscus) are c-shaped cartilage structures within each knee. They sit between the bottom of the femur (thigh bone) and the top of the tibia (shin bone). The medial meniscus is on the inside of your knee joint and the lateral meniscus is on the outer side.

As your knee flexes, the meniscus allows for a smooth gliding motion and stops the bones from rubbing together. It also acts as a shock absorber, reducing the impact on your knee joint if you're running or undertaking any other kind of physical activity.

The outer third of the meniscus has a blood supply and is known as the 'red zone'. The rest of the meniscus has no blood supply and is called the 'white zone'. If this area is damaged, it is unlikely to heal by itself.

What is a meniscal injury?

A meniscus tear is a common sports injury and can affect people of all ages. Knee arthritis can also lead to a meniscal injury, as the degeneration of the cartilage in the knee makes the menisci more susceptible to damage.

Meniscus tears are typically categorised in six ways:

• Radial tear: The most common type of meniscus injury. Radial meniscus tears are more common on the inner part of the cartilage, the medial meniscus, which is the white zone. If symptoms do not respond well to physiotherapy or rest, surgery can be performed to remove the affected cartilage.
• Horizontal tear: Running from the top to the bottom of the cartilage's C shape, horizontal tears are treated differently depending on exactly where they occur. Injuries closer to the red zone are better suited to repair procedures, while larger tears and those in the white zone may be treated with the removal of the cartilage.
• Bucket-handle tear: A common meniscus injury when a crescent-shaped cut forms in the cartilage. The resulting loose part of cartilage can, in some cases, get lodged in the knee joint and prevent a full range of movement as well as cause pain.
• Incomplete tear: This is damage that occurs over time through wear and tear and may be the result of the cartilage becoming thinner and weaker rather than a sudden impact or movement. Physiotherapy, rest and medication are commonly utilised to treat this type of tear.
• Oblique tear: Also known as a 'flap tear'. These tears are often characterised by a 'catching' sensation as the flap is agitated by the movement of your knee.
• Complex tear: A tear that features patterns and characteristics of multiple tear types. These tears carry an extra risk of further complications and the risk of developing or worsening arthritis, so surgery is typically recommended. 

Meniscus injuries can sometimes occur at the same time as other issues within the knee, such as ACL injuries in those who suffer high impact through the joint.

Causes of meniscal injuries

In younger people, menisci are tough and rubbery but can tear when the knee is twisted with force. In older people, they become less elastic and can be torn during milder activities such as squats.

Meniscal tears can typically be categorised in two ways:

• Traumatic tears: Sudden movements or changes of direction can cause your knee to hyperextend or twist unnaturally, which can result in a torn meniscus. This is common in sports such as football or dance.
• Degenerative tears: Cartilage wears down over time, so older people may sustain a meniscal injury without as much physical exertion. This experience may also affect people whose job or choice of exercise puts strain on the knee joint – for example, activities that involve heavy lifting.

How are meniscus injuries diagnosed?

Our consultants will carry out a physical assessment of your knee to see how well you can move it. They'll also ask you what you were doing when your knee began to hurt, and whether you have injured the knee in the past.

If your consultant suspects you have a meniscal tear, they may recommend an MRI scan. This will help them see the extent of the tear and whether the torn meniscus is obstructing the joint. If this is the case and your knee is locked, they may recommend surgery. Sometimes an X-ray is done if there’s a suspicion of other problems, like arthritis or fractures. 

Treatment options for a meniscus injury

It's important to reduce the pain and swelling in the knee, so your doctor will recommend anti-inflammatory medications and ice packs in the first instance. This helps to settle the symptoms of meniscal tears in most people. The size of your meniscus injury will play a significant role in how it is treated. Smaller tears in or close to the red zone of the meniscus may respond well to non-surgical options. However, tears of 2cm or more typically need surgical intervention. 

• Physiotherapy: Exercises will not heal the tear in the meniscus but strengthening the surrounding muscles can stabilise the joint, potentially reducing stiffness and pain. Physiotherapy for meniscus injuries typically focuses on improving strength and stability in the major leg muscles such as the calves, quadriceps and hamstrings.
• Meniscal repair: If you injure your meniscus in an area with a blood supply, then meniscal repair may be suitable. This keyhole surgery involves closing the tear in your meniscus using sutures and allowing it to heal over time. Physiotherapy will likely be recommended as part of your recovery process.
• Meniscus removal: If your knee is locked or other treatment options have not eased your symptoms, your doctor may recommend surgery to remove the portion of the meniscus caught in the knee joint. This procedure is known as a meniscectomy and the torn part of the meniscus is removed. 
• Meniscus transplant: In rare cases, you may be suitable for a transplant, where healthy meniscus tissue is taken from a human donor and placed into your knee joint. 
• Knee replacement: This is only appropriate if there is significant arthritis in the knee as well, together with ongoing pain, stiffness and dysfunction.