Hip Joint Ligaments
The hip joint is a ball-and-socket joint reinforced by three powerful extracapsular ligaments and one intracapsular ligament. These ligaments tighten in full extension (the close-packed position), making the standing human hip exceptionally stable.
✦ The Mnemonic
"In Practice, Inherent Ligaments Tighten"
Iliofemoral, Pubofemoral, Ischiofemoral — three capsular ligaments + Ligamentum Teres
Clinical Breakdown
All three extracapsular ligaments spiral around the femoral neck and tighten in extension — this is why standing requires minimal muscle effort (the ligaments 'lock' the hip). In flexion the ligaments relax, and the hip is much more susceptible to dislocation. The iliofemoral ligament (anterior capsule) is the largest, strongest ligament in the human body.
Hip dislocation is almost always posterior (95%) — the femoral head exits the posterior-inferior capsule (weakest point) when the hip is flexed and adducted (dashboard injury in RTA). The resultant limb position is: flexed, adducted, internally rotated. The sciatic nerve is at risk. Anterior dislocations produce the opposite posture: extended, abducted, externally rotated.
The foveal artery (from the obturator artery) runs within the ligamentum teres and contributes minimally to femoral head blood supply in adults (significant in children). The dominant supply is the medial and lateral circumflex femoral arteries, which form a ring around the femoral neck and ascend via retinacular vessels. Damage to this ring in a displaced femoral neck fracture causes avascular necrosis.
⭐ Clinical Pearl
Garden classification of intracapsular femoral neck fractures: I (incomplete/valgus impacted), II (complete undisplaced), III (partially displaced), IV (fully displaced). Garden III–IV have high AVN rates due to disruption of the retinacular blood supply. Internal fixation is preferred in younger patients; hemiarthroplasty or total hip replacement in the elderly.