• The hip socket is called the ‘acetabulum’
• Around the rim of the socket there is a little lip of cartilage – the ‘labrum’
• An acetabular labral tear is where this lip of cartilage around the rim tears
• It causes sharp catching pains in the hip – often felt in the groin or thigh
• If symptoms fail to settle with rest / physiotherapy then you need to see a specialist surgeon
• The best investigation is a 3T (a high-res 3-Tesla) MRI scan
• Treatment can be rehabilitation or hip arthroscopy (keyhole surgery of the hip)

What is the acetabular labrum?

The acetabulum is the socket of the hip joint, within the bones of the pelvis. The acetabular socket is lined with a layer of smooth articular cartilage, which is extremely low friction and which also provides some degree of shock absorbency. The peripheral rim of the acetabulum is surrounded by a lip of fibrocartilage (elastic cartilage, like the cartilage of the outer ear), called the acetabular labrum. This labrum deepens the socket and also helps to provide a suction effect, aiding in the lubrication of the joint.

The acetabular labrum is a rim of elastic cartilage around the edge of the socket of the hip, and, just like the knee cartilages, can tear causing symptoms in the joint.

Why and how do labral tears occur?

The acetabular labrum can tear through sudden major trauma to the hip joint, or through repeated minor trauma (such as high impact sports). Alternatively, the labrum can suffer ‘wear and tear’ as part of a slow onset of degeneration within the hip, either with or without evidence of more general arthritis in the joint. A labral tear can also occur with an abnormally shaped femoral head, which causes femoroacetabular impingement.

What are the symptoms?

Tears of the acetabular labrum often cause:-

• Activity-related sharp groin or anterior thigh pain
  pain that may be worse with internal rotation and/or flexion of the hip. This pain may be sharp, with catching sensations.
• Deep clicking within the hip joint (normally felt deep within the groin).
• Feeling of giving way within the hip.

How is it investigated?

Traditional investigations such as X-rays, CT-scans, Ultrasound or even basic MRI are notoriously bad at diagnosing acetabular labral tears. The best way to confirm the presence of a clinically suspected tear is to have a high-resolution 3-Tesla MRI scan.  An MR-arthrogram, which is an MRI scan combined with injecting the hip joint with a special dye, may sometimes be required – this has a diagnostic accuracy of about 90%.

MR-arthrogram showing a labral tear (the white blob, highlighted by the yellow arrow).

What is the treatment?

Labral tears may be treated with physiotherapy. Evidence suggests that this can often provide good long-term benefits. However, hip arthroscopy (keyhole surgery of the hip) may provide better longer-term benefits for acetabular labral tears. It is a technique that enables labral tears to either be trimmed or repaired, as appropriate, depending on how ragged or severe the tear might be.

Intra-operative view of a labral tear (white flap coming from the top right of the image) seen at the time of hip arthroscopy.