Ligament of the Femoral Head: Anatomy, Function, and Clinical Significance

What is the ligament of the femoral head?

The ligament of the femoral head, formally known as the ligamentum teres femoris or the round ligament of the femur, is a small, intra-articular ligament situated deep within the hip joint, connecting the fovea capitis of the femoral head to the acetabular notch.

Anatomy and Location

The ligament of the femoral head is a unique structure due to its location inside the joint capsule but outside the synovial cavity (though it is covered by a synovial sheath). It originates from two bands at the acetabular notch, inserting into the fovea capitis, a small depression on the femoral head. It is enveloped by a synovial membrane, allowing for smooth movement within the joint. While relatively small, its strategic position makes it an interesting subject in hip biomechanics.

Structure and Composition

This ligament is primarily composed of dense fibrous connective tissue, providing tensile strength. Crucially, it contains a small artery, the foveal artery (or obturator artery branch), which contributes to the blood supply of the femoral head, particularly significant during early childhood development. In adults, its contribution to the femoral head's blood supply diminishes as other sources (medial and lateral circumflex femoral arteries) become dominant. It also contains nerve fibers, suggesting a potential proprioceptive role.

Functional Role

The precise biomechanical function of the ligamentum teres in adults is a topic of ongoing research and debate. Historically, it was considered a vestigial structure with minimal mechanical importance. However, current understanding points to several potential roles:

• Minor Stabilizer: While not a primary stabilizer of the hip joint (that role falls to the strong extracapsular ligaments like the iliofemoral, pubofemoral, and ischiofemoral ligaments), some studies suggest it may provide subtle stability, especially at the extremes of hip flexion, adduction, and external rotation. It becomes taut during these movements, potentially limiting excessive motion.
• Vascular Supply: As mentioned, it carries the foveal artery, which is vital for the blood supply to the epiphysis of the femoral head in children. Damage to this ligament or artery in childhood can lead to avascular necrosis of the femoral head (Legg-Calvé-Perthes disease).
• Proprioception: The presence of nerve endings within the ligament suggests it may contribute to proprioception, providing the central nervous system with information about hip joint position and movement, which is crucial for motor control and balance.

Clinical Significance

Despite its small size, the ligament of the femoral head can be a source of hip pain and dysfunction.

• Tears: Tears of the ligamentum teres can occur due to trauma (e.g., falls, sports injuries involving twisting or hyperextension) or degenerative changes. Symptoms often include deep groin pain, clicking, catching, and instability.
• Associated Conditions: Ligamentum teres pathology is frequently associated with other hip conditions, such as:
  • Femoroacetabular Impingement (FAI): Abnormal contact between the femur and acetabulum can impinge and damage the ligament.
  • Hip Dysplasia: Instability due to a shallow acetabulum can put increased stress on the ligament.
  • Osteoarthritis: Degenerative changes in the hip joint can also affect the ligament.
• Diagnosis and Treatment: Diagnosis typically involves a combination of patient history, physical examination, and advanced imaging (e.g., MRI with contrast). Treatment options range from conservative measures (rest, physical therapy, pain management) to surgical intervention (arthroscopic debridement or repair) in cases of significant tears or persistent symptoms.

Importance for Movement Professionals

Understanding the ligament of the femoral head is valuable for fitness enthusiasts, personal trainers, and kinesiologists for several reasons:

• Comprehensive Assessment: Awareness of this ligament allows for a more thorough understanding of potential sources of hip pain, especially deep, insidious groin pain not explained by more common muscle strains.
• Injury Prevention: While direct strengthening of this ligament is not possible, understanding its role in extreme movements can inform exercise selection and technique, potentially reducing risk in athletes involved in sports with high hip demands.
• Rehabilitation: For clients recovering from hip injuries or surgery, knowing the role of the ligamentum teres can help tailor rehabilitation programs that consider hip stability, proprioceptive training, and gradual return to activity, particularly if the ligament was implicated in the injury.
• Client Education: Being able to explain the anatomy and potential issues of lesser-known structures like the ligamentum teres enhances a professional's credibility and helps clients better understand their bodies and recovery processes.