Have you ever heard of femoracetabular impingement in a child? My 11-year-old just had an MRI to confirm this is what’s causing his hip pain. This is a new term for us. We are just trying to understand what it is.

Femoracetabular impingement (FAI) refers to a pinching of the soft tissues around the hip joint where the femoral head (top of the thigh bone) bumps up against the acetabulum (hip socket).

The reason FAI occurs is because there is an abnormal relationship between the femoral head and neck. The junction where these two structures meet is shortened or rotated from normal. This change from normal is referred to as the femoral head-neck offset.

The most common causes of this problem in children are pediatric conditions such as Legg-Calvé-Perthes disease and Slipped Capital Femoral Epiphysis (SCFE). In some cases, FAI occurs when the bones are formed with slight variations from the norm. This is referred to as idiopathic anatomic variations. Idiopathic means no one knows what causes it to happen — the child is just born that way.

Repeated flexion (bending) of the hip is the movement that makes the impingement the worst. Over time, it can lead to tears of the labrum and early signs of arthritis. The labrum is a dense ring of fibrocartilage that is attached around the rim of the acetabulum. It helps make the socket deeper and more stable for the femoral head.

FAI can be treated conservatively. In fact, nonoperative care is always recommended first. This usually consists of at least six weeks of nonsteroidal antiinflammatory drugs (NSAIDs), steroid injections, physical therapy, and activity modification. In cases where the pain is severe and unchanged by therapy, surgery may be needed.