Explaining Isaiah Thomas’ Hip Impingement

May 22nd, 2017

The Boston Celtics announced on Saturday that Isaiah Thomas, their 28-year-old star point guard, re-aggravated a “right femoral-acetabular impingement with labral tear” in game two of the Eastern Conference Finals against Cleveland. The injury will keep him out for the remainder of the playoffs and may require surgery. The initial insult to the hip occurred on March 15th and it was evidently exacerbated in a semifinal round contest on May 12th.

First a little anatomy

The hip is a ball and socket joint that offers freedom of movement in three planes as well as translational movement that some conclude contributes an additional three degrees of freedom. The ball is the head of the femur, and the acetabulum is the concave socket in the pelvis. It is deepened by the presence of the labrum, a fibrocartilagenous structure that rings the area, providing a seal that increases the stability of the joint.

What is Femoroacetabular Impingement (FAI)?

When abnormal contact occurs between the head of the femur and the acetabulum, it generally results in damage to the labrum and to the smooth cartilage that surfaces the acetabulum and femoral head.

This abutment of the two structures is caused either by an acetabulum that extends out over the ball of the femur further than it should, or an irregularly shaped femoral head and abnormal junction between the neck and head of the femur. The former is known as a Pincer type FAI and the latter a Cam FAI.

These bony abnormalities can result either developmentally or in response to trauma. However, the majority of cases have been found to have a developmental predisposition. It is possible to have the underlying features without ever experiencing symptoms in the absence of consistent overload to the joint.

With a Cam impingement, the extremes of motion of the hip joint increase the compression and shearing stresses to the joint surfaces. This is particularly so for hip flexion (bending), adduction (moving toward and across the midline of the body bringing the leg toward the opposite side) and internal (inward) rotation. The offending motions in a Pincer impingement can vary depending on the specific nature of the bony abnormality. However, both pincer and Cam hip impingements result in degenerative (arthritic) changes.


Imaging studies can help identify the nature of the injury. In addition to noting inflammation and bony abnormalities, measures are taken to quantify the anatomic deformity.

In some cases, rehab to promote increased hip range of motion and strengthening of the hip musculature can resolve symptoms. Should conservative management prove insufficient, or In the presence of more pronounced pathology, surgery may be indicated. Generally performed with a scope, the procedures involved may include cleaning debris from the area, smoothing the joint cartilage, repairing a torn labrum, and shaving irregular bony surfaces to decrease surface contact.