The ligamentum teres femoris, or the round ligament of the hip joint, is a small, intra-articular ligament connecting the thigh bone to the hip socket. This structure has gained increased clinical attention due to its role in chronic hip pain. Although it was once considered a vestigial remnant, current research confirms it is a functionally important tissue within the hip joint. It is distinct from the ligamentum teres hepatis, which is a fibrous remnant of the umbilical vein found in the liver.
Anatomical Placement and Structure
The ligamentum teres femoris runs deep inside the hip joint, connecting the head of the femur (thigh bone) and the acetabulum (hip socket). Specifically, it originates from the acetabular notch and the transverse ligament at the base of the hip socket. From this broad origin, the ligament narrows and extends to insert into a shallow depression on the head of the femur called the fovea capitis.
It is classified as an intra-articular but extrasynovial ligament, meaning it is inside the joint capsule but outside the protective synovial membrane. This cord-like structure is primarily composed of dense collagen fibers, containing types I, III, and IV collagen, and its typical length is between 30 and 35 millimeters. Histological studies also reveal the presence of nerve endings and blood vessels running along its length.
Primary Roles and Function
The ligamentum teres performs two primary functions: providing minor mechanical stability and acting as a vascular conduit. While the main hip capsule ligaments provide static restraint, the ligamentum teres serves as a secondary stabilizer. It helps limit excessive rotational and lateral movement, restricting motion particularly at the extremes of hip flexion, adduction, and external rotation. This function prevents the femoral head from subluxating, or partially dislocating, during strenuous activities.
It also acts as a vascular conduit, transporting the foveal artery (a branch of the obturator artery) to supply blood to the femoral head. This function is particularly significant in infants and young children for bone growth. In adults, the blood supply through the ligamentum teres diminishes in importance as other sources take over. The ligament also contains nerve endings, including mechanoreceptors, which contribute to proprioception (the body’s sense of joint position).
Mechanisms of Injury and Symptoms
Injury results from trauma or repetitive stress. Major trauma, such as a high-force hip dislocation or subluxation, can cause an immediate and complete rupture of the ligament. More commonly, tears result from chronic microtrauma, often seen in athletes requiring frequent pivoting, twisting, or hyper-abduction.
The ligament is frequently damaged in conjunction with underlying structural hip issues like femoroacetabular impingement (FAI) or hip dysplasia, where abnormal bone shape causes chronic irritation. When injured, the most common symptom is deep, poorly localized pain in the groin area. Patients often report mechanical symptoms, such as a painful clicking, catching, or locking sensation within the hip joint during movement. This instability is a direct result of the ligament’s inability to provide stabilizing restraint.
Treatment Approaches for Ligament Damage
The management of a ligamentum teres injury typically begins with non-operative treatments, especially for minor strains or partial tears. Conservative care focuses on reducing inflammation and pain using rest, activity modification, and non-steroidal anti-inflammatory drugs (NSAIDs). Physical therapy is then used to strengthen the surrounding hip muscles, which improves joint control and dynamic stability to compensate for the compromised ligament.
If conservative measures fail to relieve symptoms, surgical intervention is often recommended, usually performed using minimally invasive hip arthroscopy. The most frequent surgical procedure is debridement, which involves trimming or removing the damaged tissue. For complete rupture or significant instability, reconstruction using a tissue graft may be considered, though this is a less common and more complex procedure.