Ligamentum Teres Femoris: Anatomy, Functions, and Clinical Significance

What is the ligament of the head of the femur?

The ligament of the head of the femur, also known as the Ligamentum Teres Femoris or Round Ligament of the Femur, is an intra-articular but extrasynovial ligament that connects the fovea capitis of the femoral head to the acetabular notch within the hip joint, primarily serving as a conduit for blood supply and contributing to proprioception.

Introduction to the Ligamentum Teres Femoris

The hip joint, a marvel of biomechanical engineering, relies on a complex interplay of bones, cartilage, muscles, and ligaments for its remarkable stability and mobility. Among its various stabilizing structures, the Ligamentum Teres Femoris stands out due to its unique anatomical position and multifaceted, though often underestimated, roles. Unlike the powerful capsular ligaments (iliofemoral, pubofemoral, ischiofemoral) that provide significant passive stability, the Ligamentum Teres offers a different kind of contribution to hip joint health and function.

Anatomy and Location

The Ligamentum Teres Femoris is a roughly triangular or flat band of connective tissue situated deep within the hip joint.

• Origin: It originates from the fovea capitis, a small depression located on the superior aspect of the femoral head.
• Insertion: From this point, it extends proximally and medially to insert into the acetabular notch and the adjacent transverse acetabular ligament within the acetabulum (the socket of the hip joint).
• Structure: Composed primarily of collagen fibers, it also contains some elastic fibers and is covered by a synovial sheath, although it remains outside the true synovial cavity (intra-articular but extrasynovial). Its size and robustness can vary significantly among individuals.

Primary Functions

While often considered a vestigial structure or a minor stabilizer, contemporary research highlights the Ligamentum Teres Femoris as having several critical functions:

• Blood Supply Conduit: This is arguably its most vital role, particularly during childhood and adolescence. The ligament encases the artery to the ligament of the head of the femur (also known as the acetabular branch of the obturator artery, or less commonly, a branch of the medial circumflex femoral artery). This artery provides a crucial, albeit variable, contribution to the blood supply of the femoral head, especially its epiphysis. In adults, other arterial networks typically provide the primary blood supply, but the contribution from the Ligamentum Teres artery can still be significant in specific regions of the femoral head.
• Proprioception: The Ligamentum Teres is richly innervated with mechanoreceptors and nociceptors. These nerve endings play a crucial role in proprioception (the body's sense of its position and movement) and nociception (pain perception). This means the ligament contributes to the brain's awareness of hip joint position, movement, and potential overstretching or injury, thereby influencing muscle activation patterns for joint protection.
• Minor Mechanical Stability: While not a primary stabilizer, the ligament provides some degree of mechanical stability, particularly when the hip is in positions of flexion, adduction, and external rotation. In these positions, it becomes taut, offering a subtle check to excessive motion and helping to maintain the congruity of the joint surfaces.

Blood Supply Considerations

The artery contained within the Ligamentum Teres is of particular clinical importance:

• Pediatric Hip Health: In children and adolescents, this artery can be a significant source of blood flow to the developing femoral head. Compromise of this blood supply (e.g., due to trauma, inflammation, or certain diseases like Legg-Calvé-Perthes disease or slipped capital femoral epiphysis) can lead to avascular necrosis (death of bone tissue due to lack of blood supply) of the femoral head, with potentially devastating long-term consequences for hip function.
• Adult Contribution: Although the adult femoral head receives its dominant blood supply from the medial and lateral circumflex femoral arteries, the artery within the Ligamentum Teres still contributes, especially to the foveal and superior aspects of the femoral head.

Clinical Significance and Injuries

Pathology of the Ligamentum Teres Femoris is increasingly recognized as a source of hip pain and dysfunction.

• Traumatic Tears: Tears can occur due to acute trauma, such as hip dislocations, falls, or forceful twisting injuries, especially those involving hip flexion, adduction, and external rotation. These tears can be partial or complete.
• Degenerative Changes: The ligament can undergo degenerative changes over time due to chronic microtrauma, repetitive stress, or age-related wear.
• Association with Other Pathologies: Ligamentum Teres injuries are often found concurrently with other hip pathologies, including femoroacetabular impingement (FAI), hip dysplasia, and labral tears. It can be a direct source of pain in FAI.
• Symptoms: Patients with Ligamentum Teres injuries may experience deep groin pain, clicking, catching, instability, or a sense of giving way in the hip.
• Diagnosis: Diagnosis typically involves a combination of clinical examination, advanced imaging (such as MRI with contrast), and often confirmed via hip arthroscopy, which allows direct visualization of the ligament.

Rehabilitation and Management

Management of Ligamentum Teres injuries depends on the severity of the tear, the presence of other hip pathologies, and the patient's symptoms and activity level.

• Conservative Management: For minor injuries or in cases where symptoms are mild, conservative approaches may be employed. This includes rest, activity modification, anti-inflammatory medications, and targeted physical therapy to improve hip strength, stability, and neuromuscular control.
• Surgical Management: In cases of significant tears, persistent pain, or mechanical symptoms, arthroscopic surgery is often considered. Surgical options include debridement (removal of damaged tissue), partial resection, or, less commonly, repair or reconstruction of the ligament. The goal is to alleviate pain, restore hip mechanics, and prevent further joint degeneration.

Conclusion

The ligament of the head of the femur, the Ligamentum Teres Femoris, is far from a mere anatomical curiosity. Its roles as a crucial conduit for blood supply to the femoral head, a significant contributor to hip proprioception, and a minor mechanical stabilizer underscore its importance in maintaining overall hip joint health and function. Understanding its anatomy, functions, and potential pathologies is essential for clinicians, fitness professionals, and individuals seeking to comprehend the intricate workings of the human hip.