The glenoid labrum is a donut shaped ring of gristle that serves to deepen the socket on the scapula for the shoulder joint. It helps to stabilise and strengthen the function of the shoulder joint.

The glenoid fossa is the name given to the "socket" area of the ball and socket joint.

The glenoid labrum varies in size in different people and - a bit like a cartilage or meniscus in the knee - it has a wedge like shape in cross section.

The attachment of the labrum is usually continuous with the edge of the socket or fossa and blends directly into the joint surface.

The labrum is a primary site for the attachment of the shoulder joint capsule and for ligaments inside the joint. A healthy labrum is vital for the normal function of the shoulder joint. A tear in the labrum is a relatively common cause of shoulder pain in the younger athletic population.

At the top aspect of the glenoid labrum lies the attachment for the long head of the biceps muscle. This attachment site is vulnerable to injury and to age related degenerate changes.

Injury to the glenoid labrum is divided into SLAP or Non SLAP lesions.

SLAP stands for "Superior labrum (tear) Anterior to Posterior"

 SLAP tears are either stable or unstable and this depends on how much of the labrum has been torn free from the joint - and also on whether the biceps tendon is still attached.

The commonest cause of a SLAP tear is an acute traction or acute compression injury - with downward force on the shoulder.

Traction injury is common in athletes who use the arm in the overhead position and are seen in those who perform repeated tasks in this position.

Weight lifters, swimmers, pitchers, cricketers and tennis players are among those most at risk.

Compression injury to the labrum is often caused due to a fall onto an outstretched arm with the shoulder forward flexed. SLAP lesions can occur in isolation or in association with dislocation or subluxation of the joint.

People who have sustained a SLAP tear complain of pain in the shoulder made worse by overhead or behind the back movements.

SLAP tears often produce a sense of popping or sticking in the shoulder joint - along with feelings of something grinding or rubbing.

In older patients a chronic SLAP tear can mimic the presentation of a frozen shoulder

On examination the doctor often finds tenderness over the front of the shoulder joint capsule and pain on resisted contraction of the biceps muscle. Several "special examination tests" have been devised for SLAP tears but none of them are very reliable on their own, although they are better if used in combination with each other.

A normal x-ray will often show no abnormality even when a large SLAP tear is present. MRI with contrast arthrogram is the investigation of choice to pick up the problem

 All patients with a proven SLAP tear will need surgery. Some doctors in the past advocated trying conservative and physical therapy based treatments first but the evidence is now very convincing that these don't work.

Unstable SLAP tears need arthroscopic surgery to reattach the torn labrum and to repair the biceps tendon.

Stable SLAP tears respond well just to arthroscopic tidying up of the damaged tissues.

The surgeon doing the operation needs to carefully check for shouder instability because surgery may also be required to correct this or the SLAP tear repair will not work.