A tear in the hip labrum is a laceration of the cartilage in the socket of the hip joint, states Mayo Clinic. An extra bone in a joint is called an accessory ossicle and is formed in the tendon of a joint, according to the Missoula Foot and Ankle Group.
The labrum is a circlet of cartilage around the outer rim of the socket of the hip joint, explains Mayo Clinic. This ring of tissue acts as a seal to securely enclose the ball on the end of the femur where it rests in the hip joint socket. Labral tears are caused by arthritis and sports injuries, but more often as a result of femoroacetabular impingement, a condition in which the ball and joint of the socket do not fit together properly, according to the University of California at San Diego. Hip labral tears increase the chances of osteoarthritis developing over time, reports Mayo Clinic.
Accessory ossicles typically form within a tendon where the tendon rubs against a bone, although they are sometimes caused by portions of bone that never fused together during childhood, explains the Missoula Foot and Ankle Group. These extra bones usually form in the foot, but they can occur near almost any joint and are generally asymptomatic.