The femoral head is the spherical proximal end of the femur that articulates with the acetabulum to form the hip joint. It represents approximately two-thirds of a sphere and is covered entirely by articular cartilage except at the fovea capitis, a small pit near the centre of the head where the ligamentum teres attaches. The blood supply to the femoral head in adults comes primarily from the medial femoral circumflex artery branches, with the ligamentum teres artery contributing minimally.
The femoral head is vulnerable to avascular necrosis (AVN) due to its dependence on the medial femoral circumflex artery supply, which can be disrupted by femoral neck fractures, dislocation, high-dose corticosteroids, excessive alcohol consumption, sickle cell disease, and decompression illness. AVN progresses through stages from subchondral marrow oedema to subchondral collapse producing the crescent sign, ultimately ending in femoral head collapse requiring total hip arthroplasty. Slipped capital femoral epiphysis in adolescents involves displacement of the femoral head epiphysis on the neck.
Ischaemia of the femoral head from vascular disruption or non-traumatic causes produces progressive bone death, subchondral fracture (crescent sign on MRI), and articular surface collapse requiring protected weight-bearing in early stages and total hip arthroplasty for advanced collapse.
Physeal instability in obese adolescent males allows the femoral head to slip posteromedially on the neck, producing a painful Trendelenburg gait and limited internal rotation, requiring urgent in situ pinning to prevent further slip and AVN.
