Made of tough cartilage, the labrum rings the hip’s socket, or acetabulum. The labrum is important to overall hip health and function. Specifically, the labrum:
- Facilitates the hip's range of motion, allowing the thigh to rotate in every direction, including forward, backward, inward, and externally
- Helps preserve proper alignment between the hip’s ball and socket
- Keeps synovial fluid, or joint fluid, within the hip joint capsule (synovial fluid reduces stress and friction and allows for smooth movement between the ball and socket)
In essence, the hip labrum is a ring of cartilage that provides both support and flexibility to the joint. When the labrum is damaged, the hips range of motion, alignment, and synovial fluid can be affected.
Structure of Hip Labrum
The labrum is shaped like a ring. The size and thickness of the hip labrum varies from person, and even from one hip to another, but in general an adult labrum:
- Has an average circumference of around 16 cm for males and 14 cm for females1
- Is 2 mm to 3 mm thick2
Hip labrums are typically wider and thinner in the at the front of the hip, and thicker at the back of the hip.2
The labrum is composed of fibrocartilage. Fibrocartilage contains woven layers of collagen fibers, making it the strongest type of cartilage.3 The labrum’s composition allows it to withstand the stressors and demands of sports, such as running and gymnastics, that require significant range of motion and flexibility.
Another type of cartilage, called articular cartilage, covers the surfaces of the femoral head (the hip’s ball) and acetabulum (the hip’s socket). Smooth and slippery, articular cartilage protects the bones and decreases friction.
Labral Fraying and Labral Tears
Although fibrocartilage in the hip labrum is strong, it can still become damaged. This damage, called labral fraying or a labral tear, may be caused by:
- An acute injury
- General wear and tear
People who regularly play sports that involve kicking, turning, and/or running are more likely to see labral damage than those who do not.
Fraying vs tearing
A doctor will typically describe a damaged labrum as “frayed” or “torn.”
- Labral Fraying. Generally, fraying affects a specific area of the labrum. For example, wear and tear from frequent kicking or dancing may cause a few centimeters of the labrum to fray. This damage may be treated with a surgery called debridement to smooth the damaged piece of the labrum.
- Labral Tears. In most labral tears, a portion of the labrum has detached from the hip’s socket. This type of labral damage typically requires surgery to reattach the labrum to the bone.
Either type of damage can cause pain, a catching or locking feeling, and hip instability.
- Karns MR, Patel SH, Kolaczko J, et al. Acetabular rim length: an anatomical study to determine reasonable graft sizes for labral reconstruction. J Hip Preserv Surg. 2017;4(1):106-112.
- Groh MM, Herrera J. A comprehensive review of hip labral tears. Curr Rev Musculoskelet Med. 2009;2(2):105-17.
- Grant AD, Sala DA, Davidovitch RI. The labrum: structure, function, and injury with femoro-acetabular impingement. J Child Orthop. 2012;6(5):357-72.