• Hip impingement is also called ‘femoroacetabular impingement’
• It occurs when the edge of the ball of the hip joint rubs against the edge of the socket
• It causes pain in the hip, groin, thigh or even knee
• There may be sudden sharp pains or catching sensations
• If symptoms fail to settle with rest or physiotherapy then you need to see a surgeon
• An MRI scan with dye injected into the hip may be required
• Treatment can be performed with a hip arthroscopy (keyhole surgery of the hip)

What is hip impingement?

Femoroacetabular Impingement (FAI) is a condition whereby the bone at the front of the ball part of the hip joint (the femoral head) rubs against the edge of the socket (the acetabulum) when the hip is flexed up (i.e. when the knee is brought up towards the chest).

There are generally two types of FAI:

Cam – this is where the femoral head is not entirely round, and the edge of the head is therefore prominent.

Pincer – this is where the edge of the hip socket catches on the femoral head/neck.

A lot of the time, these two forms exist together.

Normal hip shape (ball and socket).

Cam-type FAI caused by bony ‘bump’ at front of femoral head/neck.

Pincer-type FAI caused by deep socket or spikes of bone (osteophytes) at front of socket.

What causes FAI?

It is not yet clear whether FAI is something that is congenital (people are born with it) or acquired (after birth) due to other factors, such as significant athletic activity before children’s bones have become mature. Symptoms may be worsened by contact sports. It is likely that FAI is most probably caused by a combination of genetic and environmental factors.

What are the symptoms of FAI?

FAI may be without symptoms for a long time. After a while, it may cause pain and stiffness in the hip joint that is often felt in the front of the groin or at the top of the thigh. The condition can stop people fully bending their hips, and the pain may be particularly bad when the knee is brought up towards the chest and the hip is flexed, especially if the thigh is rolled inwards at the same time (flexion + internal rotation of the hip). Pain may worsen after prolonged sitting, running or jumping.

How is FAI investigated?

FAI can often be seen clearly on simple X-rays, especially if there is a cam-shaped femoral head/neck present. Additional investigations, such as a CT scan and high-resolution 3T MRI scan, may also be performed. CT scanning may be useful to identify contributing factors, such as an altered position of the ball and socket joint. It also allows motion analysis to be carried out to confirm whether FAI is occurring. MRI scans can also show up other pathologies within the hip joint, such as whether there is a tear of the acetabular labrum (labral tear) or degenerative changes within the joint (thinning of the lining of the ball or the socket).

What happens if FAI is left alone?

If FAI is left untreated then it may potentially get worse with time, and the pinching of the edge of the hip may cause acetabular labral tears (tears of the rim of cartilage around the hip socket), and it is possible that with time one may subsequently begin to develop increasing arthritis in the hip joint.

What are the treatments?

If the symptoms from FAI are mild, then conservative treatments may well suffice. These can include:-

• Painkillers and anti-inflammatories.
• Physiotherapy.
• Restriction of aggravating activities (rest).

There is evidence that physiotherapy can provide good lasting outcomes. However, surgical intervention may provide better and longer-lasting outcomes.

For cases where the severity of the symptoms justifies intervention, then surgical treatment options include:-

• Intra-articular injection of the hip joint with cortisone/steroid (in theatre under X-ray control or using ultrasound guidance in the clinic or radiology department)
• Hip arthroscopy. With this technique, it is possible to shave down the excess bone at the front of the femoral head/neck and to trim or repair any labral tears that might have developed. Cartilage damage in the joint can also be treated at the same time.

Each patient will receive an individualised treatment plan tailored to their symptoms and their personal situation.