page_title: Acetabular labrum
section_title: Mechanisms of Injury
hierarchical_section_title: Acetabular labrum / Acetabular labrum tear / Mechanisms of Injury
caption_attribution_description: English: Figure 7. A complex labral tear. An arthroscopic probe is seen at the junction of the labrum and acetabular rim.
context_page_description: The acetabular labrum is a ring of cartilage that surrounds the acetabulum of the hip. The anterior portion is most vulnerable when the labrum tears.
  It provides an articulating surface for the acetabulum, allowing the head of the femur to articulate with the pelvis.
context_section_description: It is estimated that 75% of acetabular labrum tears have an unknown cause. Tears of the labrum have been credited to a variety of causes such as excessive force, hip dislocation, capsular hip hypermobility, hip dysplasia, and hip degeneration. A tight iliopsoas tendon has also been attributed to labrum tears by causing compression or traction injuries that eventually lead to a labrum tear. Most labrum tears are thought to be from gradual tear due to repetitive microtrauma. Incidents of labrum tears increase with age, suggesting that they may also be caused by deterioration through the aging process. Labrum tears in athletes can occur from a single event or recurring trauma. Running can cause labrum tears due to the labrum being used more for weight bearing and taking excessive forces while at the end-range motion of the leg: hyperabduction, hyperextension, hyperflexion, excessive external rotation. Sporting activities are likely causes, specifically those that require frequent lateral rotation or pivoting on a loaded femur as in hockey or ballet. Constant hip rotation places increased stress on the capsular tissue and damage to the iliofemoral ligament. This in turn causes hip rotational instability putting increased pressure on the labrum.
  Traumatic injuries are most commonly seen in athletes who participate in contact or high impact sports like football, soccer, or golf.  The prevalence rate for traumatic hip injuries that causes a tear of the labrum is very low. Less than 25% of all patients can relate a specific incident to their torn labrum, however they are often a result of a dislocation or fracture. Falling on one's side causes a blunt trauma to the greater trochanter of the femur. Since there is very little soft tissue to diminish the force between the impact and the greater trochanter, the entire blow is transferred to the surface of the hip joint. And since bone density does not reach its peak until the age of 30, hip traumas could result in a fracture. Tears of the hip labrum can be classified in a variety of ways, including morphology, etiology, location, or severity.
  Anatomical modifications of the femur and or hip socket cause a slow buildup of damage to the cartilage. Femur or acetabular dysplasia can lead to femoral acetabular impingement (FAI). Impingement occurs when the femoral head rubs abnormally or lacks a full range of motion in the acetabular socket. There are three different forms of FAI. The first form is caused by a cam-deformity where extra bone is present on the femoral head, which leads to the head being non-spherical. The second deformity is referred to as a pincer deformity and it is due to an excess growth of the acetabular socket. The third type of FAI is a combination of the first two deformities. When either abnormality is present, it changes the position that the femoral head occupies in the hip socket. The increased stresses that the femur and or acetabulum experience may lead to a fracture of the acetabular rim or a detachment of the overstressed labrum.
caption: A complex labral tear. An arthroscopic probe is seen at the junction of the labrum and acetabular rim.
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