Meniscal injuries of the knee are, by far, one of the more common injuries I encounter as an orthopaedic surgeon. In fact, the surgical procedure to treat these injuries i.e. knee arthroscopy is the most common operative intervention carried out in an orthopaedic theatre. Here in Malta, around 500 of these surgeries are carried out yearly.

There are two menisci. They are called the medial and lateral meniscus. These are made of fibrocartilage. They are semicircular in shape and their function is to act as buffers or shock absorbers. This cartilage structure needs to be distinguished from the glistening cartilage that covers the bones in the joints called hyaline cartilage.

Injuries to these menisci occur when the knee sustains a twisting force causing the menisci to be caught between the bones of the knee, femur and tibia, and then tear.

These injuries commonly occur in contact sports especially football but even after a simple fall or stumble. The medial meniscus is much more commonly injured than the lateral meniscus.

Meniscal tears are not visible on an X-ray as they are radiolucent

Meniscal tears are however also common in degenerate or arthritic knees. The meniscus becomes soft and frail with age, and easily tears with minimal force. This is normally on the background of worn joint surfaces.

The shape of the tear varies from a small radial or parrot beak tear to a tear of the whole meniscus, called a bucket handle tear. The tear may appear in the inner part of the meniscus or the outer rim.

A knee with a torn meniscus

A patient who sustains a meniscal tear typically has a painful swollen knee and difficulty weight bearing. Later symptoms include mechanical symptoms, notably locking and giving way. There may be associated injuries in the knee, including collateral ligament or cruciate ligament tears.

Meniscal tears are not visible on an X-ray as they are radiolucent. The investigation of choice to diagnose meniscal tears is an MRI scan. This investigation may also pick up any other associated injuries including ligament injuries.

The problem with most meniscal tears is that they do not heal in view of the paucity of blood supply, particularly on the inner parts of the meniscus. In view of this, they may keep causing mechanical problems if left untreated.

Conservative treatment – such as rest, ice and medication – is sometimes enough to relieve the pain of a torn meniscus and give the injury time to heal on its own. In other cases, however, a torn meniscus requires surgery.

Historically this was performed via an open total resection, but this eventually results in increased degeneration of the knee cartilage surfaces and hence arthritis. Nowadays, only the tear is resected leaving the majority of the meniscus behind. This is performed with minimally invasive keyhole or arthroscopic surgery.

This is normally performed as a day case and recovery is within three weeks. Some large meniscal tears particularly peripheral ones where the blood supply is intact may actually be repairable using sutures, particularly in younger patients.

Alistair Melvyn Pace, Consultant orthopaedic surgeon