Does Your Hip Click? Maybe It’s FAI (Femoroacetabular Impingement)

femoroacetabular impingement FAI

The body makes sounds. Sometimes it’s just gas bubbles popping inside of a joint, sometimes it’s tendons rolling over each other, sometimes it’s bony anatomy. As a general rule of thumb, if it doesn’t hurt, it’s probably nothing to be concerned with. However, painful clicking or popping may be a sign of something lurking that should be addressed. 

There are many causes of painful popping in the hip, but one that often gets missed is FAI. FAI stands for femoroacetabular impingement. So first, a quick look at the anatomy: 

hip anatomy

Impingement simply means something is being pinched. In this case, the pinching is occuring in the ball and socket joint between the femoral head (ball) and the acetabulum (socket). This can cause damage to the cartilage, the labrum, limit range of motion, and cause pain. 

Pinching occurs because of bony growth that is not supposed to be there. Either the ball or socket develops a growth, and sometimes both. Femoroacetabular impingement falls into 3 subtypes, cam, pincer, and mixed. With a cam deformity, there is bony growth between the head and neck of the femur. This causes shearing of the labrum with hip flexion (think of bringing your knee to your chest). 

With a pincer deformity, the acetabulum (socket) develops a growth. This will cause compression of the labral with hip flexion, adduction, and internal rotation, leading to degeneration. Most commonly, people have a combination of the two, pincer and cam.

FAI

There is a lot of symptom overlap for other hip injuries but the most common complaint is groin pain that gets worse with sport activity. It can also be provoked by prolonged sitting, standing, and walking. Walking up a hill can be painful and sometimes patients will report pain in the SI joint (back of the pelvis/sacrum) or into the buttock. Sharp pain may be felt with clicking or a sensation of the leg giving out. Sports that require a lot of pivoting will provoke the pain. When asked where the pain is, the “C sign” is the classic presentation as depicted below:

“C-sign”

“C-sign”

X-ray is usually sufficient to diagnose FAI. If there is soft tissue involvement, an MRI may be ordered. Physical therapy can test for it with the FADIR and FABER tests.

FADIR/FABER

FADIR/FABER

Physical therapy is usually successful in treating FAI and will be focused on strength, restoring range of motion, symptom reduction, and potentially capsular stretching if indicated. Sometimes stiffness of the hip capsule affects the normal roll and glide mechanics of the ball and socket. Freeing up some space within the joint may be all it takes to reduce symptoms depending on severity. For those that do not respond to conservative therapy, surgery is an option and has good outcomes. Surgical repair has the advantage of reducing the chances of arthritis in the hip.