Ligamentum Teres: Anatomy, Functions, and Clinical Relevance

What is the meaning of ligament teres?

The ligamentum teres, also known as the round ligament of the femur, is an intra-articular yet extrasynovial ligament within the hip joint that connects the femoral head to the acetabulum, playing a role in hip stability and, critically, housing a vital artery supplying the femoral head, particularly during childhood.

Anatomical Definition and Location

The ligamentum teres femoris (Latin for "round ligament of the femur") is a unique structure located deep within the hip joint capsule. It originates from the transverse acetabular ligament and the margins of the acetabular notch, then extends superiorly and laterally to insert into the fovea capitis femoris, a small depression on the head of the femur.

Despite being located within the joint capsule (intra-articular), it is considered outside the synovial membrane (extrasynovial). This means it is bathed in synovial fluid but not directly covered by the synovial lining, a characteristic that differentiates it from other intra-articular structures. Its average length is approximately 30-35 mm, with a diameter of 5-8 mm, varying between individuals.

Functional Role and Significance

The ligamentum teres serves multiple important functions:

• Mechanical Stability: While not a primary stabilizer of the hip joint (a role predominantly played by the strong iliofemoral, pubofemoral, and ischiofemoral ligaments), the ligamentum teres contributes to hip stability, especially during specific movements such as adduction and flexion. It may help limit excessive external rotation and adduction when the hip is flexed. Its fibers are often taut in these positions, providing a secondary line of defense against dislocation.
• Vascular Supply: Perhaps its most critical role, particularly in early life, is to house the artery to the head of the femur, also known as the foveal artery or medial epiphyseal artery. This small artery, a branch of the obturator artery (or sometimes the medial circumflex femoral artery), provides a significant portion of the blood supply to the femoral head and epiphyseal plate during childhood and adolescence. While its contribution diminishes in adulthood as other vascular sources mature, it can still provide collateral circulation in cases of femoral neck fracture or avascular necrosis.
• Proprioception: Emerging research suggests the ligamentum teres may also contain mechanoreceptors and nerve endings, implying a potential role in proprioception – the body's ability to sense its position and movement. This sensory input could contribute to neuromuscular control and dynamic stability of the hip joint.

Clinical Relevance and Pathologies

Injuries to the ligamentum teres, though historically considered rare, are increasingly recognized with advancements in diagnostic imaging and arthroscopic techniques.

• Injury Mechanisms:
  • Traumatic: Often associated with hip dislocation, subluxation, or direct impact.
  • Repetitive Microtrauma: Common in athletes involved in sports requiring extreme hip rotation, flexion, or pivoting movements (e.g., dancers, gymnasts, martial artists, ice hockey players).
  • Iatrogenic: Can be injured during hip surgery.
  • Associated with Hip Dysplasia or Impingement: Abnormal hip mechanics can predispose the ligament to injury.
• Symptoms: Patients typically report deep, anterior hip or groin pain, which may be exacerbated by specific movements or prolonged sitting. Other symptoms can include clicking, catching, locking, or a sensation of instability within the hip joint.
• Diagnosis: Diagnosis can be challenging. Physical examination may reveal tenderness or pain with certain provocative tests. Magnetic Resonance Imaging (MRI) is often used, but definitive diagnosis frequently requires hip arthroscopy, which allows direct visualization and assessment of the ligament.
• Pathologies: Injuries range from partial tears (sprains) to complete ruptures. It can also undergo degenerative changes (ligamentum teres degeneration) or hypertrophy.
• Treatment:
  • Conservative: Rest, activity modification, anti-inflammatory medications, and physical therapy to improve hip strength and stability.
  • Surgical: Arthroscopic debridement (removal of damaged tissue) or, in select cases, reconstruction of the ligament may be considered, particularly for symptomatic tears or instability.

Importance in Specific Populations

• Children and Adolescents: The vascular role of the foveal artery housed within the ligamentum teres is paramount in pediatric populations. Disruption of this blood supply, such as in slipped capital femoral epiphysis (SCFE) or traumatic hip dislocation, can lead to avascular necrosis of the femoral head, a serious condition that can result in long-term disability.
• Athletes: Individuals participating in sports that involve extreme hip range of motion, sudden changes in direction, or repetitive twisting forces are at higher risk for ligamentum teres injuries. Recognition and appropriate management are crucial for optimal athletic performance and injury prevention.

Conclusion

Though often overshadowed by the larger, more robust ligaments of the hip, the ligamentum teres is far from insignificant. Its unique intra-articular position, crucial role in vascularizing the femoral head in early life, contribution to hip stability, and potential proprioceptive function underscore its multifaceted importance. Understanding its anatomy and clinical relevance is essential for healthcare professionals, fitness educators, and individuals seeking to comprehend the intricate mechanics of the human hip joint.