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AN17.1-3 | Hip Joint — Gate Quiz
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The hip joint is classified as which type of synovial joint?
Correct! The hip joint is a ball-and-socket (spheroidal) synovial joint — the femoral head (ball) articulates with the acetabulum (socket). It allows movement in all planes including rotation. The other ball-and-socket joint in the body is the shoulder (glenohumeral) joint.
Hip = ball-and-socket (spheroidal) joint. Allows flexion/extension, abduction/adduction, medial/lateral rotation, and circumduction. Most stable joint in the body due to deep acetabulum + strong capsular ligaments + acetabular labrum. Compare to shoulder: more mobile, less stable.
Incorrect. The hip is a ball-and-socket (spheroidal) joint. Hinge joints (elbow, ankle) allow only flexion-extension; pivot joints (atlantoaxial, radioulnar) allow rotation around a single axis.
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Which ligament of the hip joint is considered the strongest in the human body?
Correct! The iliofemoral ligament (Y-ligament of Bigelow) is the strongest ligament in the body. It is an inverted Y-shaped thickening of the anterior capsule, running from the AIIS to the intertrochanteric line. It resists hip extension and lateral rotation, preventing backward falling in the erect position.
Iliofemoral (Y-ligament of Bigelow): strongest ligament in the body; anterior; resists extension + lateral rotation. Pubofemoral: antero-inferior; resists abduction + extension. Ischiofemoral: posterior; resists extension + medial rotation. Ligamentum teres: intra-articular, weak; carries foveal artery.
Incorrect. The iliofemoral ligament (Y-ligament of Bigelow) is the strongest ligament in the human body.
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Which mechanism best explains why avascular necrosis (AVN) of the femoral head occurs after a displaced intracapsular fracture of the femoral neck?
Correct! In adults, the femoral head is primarily supplied by retinacular branches of the medial circumflex femoral artery. These vessels run in the synovial folds (retinacula) along the femoral neck. A displaced intracapsular fracture tears these vessels, cutting off blood supply to the femoral head → avascular necrosis.
Blood supply to femoral head: retinacular branches of medial circumflex femoral artery (main in adults) via retinacular folds of synovium. Displaced intracapsular fractures tear these → AVN (femoral head dies). Foveal artery (obturator) is small in adults. Treatment for displaced fractures in elderly: hemiarthroplasty to avoid AVN.
Incorrect. The critical vessels are the retinacular branches of the medial circumflex femoral artery. In adults, the foveal (obturator) artery is minimal.
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An 80-year-old osteoporotic woman sustains a displaced intracapsular femoral neck fracture (Garden IV). Which is the most appropriate surgical management and why?
Correct! In an elderly patient with a displaced intracapsular fracture (Garden III/IV), the retinacular vessels are torn → high risk of AVN if the head is preserved. Hemiarthroplasty removes the femoral head and replaces it with a prosthesis, bypassing the AVN problem. This allows early mobilisation in elderly patients, reducing complications of prolonged bed rest.
Displaced intracapsular fracture management: Elderly (>65–70) → hemiarthroplasty (or THR if ambulatory). Young (<60) → urgent reduction + internal fixation (preserve native head). Garden I/II (undisplaced) → can fixate at any age. Delay >6 hours increases AVN risk.
Incorrect. In the elderly with displaced fractures, AVN risk is too high for fixation to be reliable. Hemiarthroplasty is preferred for rapid rehabilitation.
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A 28-year-old man involved in a road traffic accident presents with inability to move his left hip. On examination, the left lower limb is in flexion, adduction, and internal rotation. The femoral head is not palpable in the femoral triangle. This is characteristic of which injury?
Correct! Posterior dislocation of the hip (the most common type, ~90%) produces a characteristic posture: flexion, adduction, and internal rotation of the affected limb, with apparent limb shortening. The femoral head is displaced posteriorly and is not palpable in the femoral triangle (unlike anterior dislocation where it may be felt anteriorly).
Hip dislocation positions: Posterior (90%): flexion, adduction, internal rotation, shortening, femoral head not in femoral triangle. Anterior (10%): flexion, abduction, external rotation, femoral head palpable anteriorly. Posterior dislocation mechanism: dashboard injury (knee hits dashboard with hip flexed). Complication: sciatic nerve injury → foot drop.
Incorrect. Posterior dislocation: flexion + adduction + internal rotation. Anterior dislocation: flexion + abduction + external rotation.
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In posterior dislocation of the hip, which nerve is most at risk of injury, and what is the resulting clinical deficit?
Correct! The sciatic nerve runs posterior to the hip joint and is vulnerable when the femoral head dislocates posteriorly. Sciatic nerve injury causes foot drop (loss of dorsiflexion due to common fibular component), weakness of plantarflexion and toe flexion (tibial component), and loss of sensation below the knee.
Sciatic nerve and posterior hip dislocation: sciatic nerve exits the greater sciatic foramen inferior to piriformis and runs posterior to the hip joint. Posterior dislocation can stretch/tear the sciatic nerve → foot drop (common fibular component) + plantarflexion weakness + sensory loss below knee. Check sciatic nerve function before and after reduction.
Incorrect. The sciatic nerve is posterior to the hip joint and is the nerve at risk in posterior dislocation.
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According to Hilton's law, the hip joint is supplied by branches of which nerves?
Correct! By Hilton's law, the nerves supplying the muscles acting on the hip joint also supply the joint. The hip joint is supplied by: femoral nerve (anterior), obturator nerve (inferior), and the nerve to quadratus femoris (branch of sciatic) posteriorly. This explains why hip pathology can present with pain in the anterior thigh (femoral), medial knee (obturator), and buttock (sciatic).
Hip joint nerve supply (Hilton's law): femoral nerve (anterior), obturator nerve (medial/inferior), sciatic nerve via nerve to quadratus femoris (posterior). Clinical significance: referred pain to anterior thigh, medial knee, and buttock can all indicate hip pathology.
Incorrect. The hip joint is supplied by branches of the femoral nerve, obturator nerve, and sciatic nerve (via the nerve to quadratus femoris).
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A 55-year-old woman complains of pain over the lateral hip that worsens when she lies on that side. She has point tenderness over the greater trochanter. Which bursa is most likely inflamed?
Correct! The trochanteric bursa lies between the greater trochanter and the overlying gluteus maximus/iliotibial band. Inflammation (trochanteric bursitis) causes lateral hip pain, worse when lying on the affected side or with iliotibial band friction during activity. Point tenderness at the greater trochanter is the hallmark.
Bursae around the hip: Trochanteric bursa (greater trochanter / gluteus maximus — lateral hip pain), Iliopsoas bursa (iliopsoas tendon / capsule — anterior groin pain, communicates with joint), Ischial bursa (ischial tuberosity / gluteus maximus — "weaver's bottom"). Trochanteric bursitis is common in runners and middle-aged women.
Incorrect. The trochanteric bursa is over the greater trochanter; point tenderness there with lateral hip pain = trochanteric bursitis.
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A patient with a superior gluteal nerve palsy shows a positive Trendelenburg sign — the pelvis drops on the opposite side when standing on the affected leg. Which muscle is paralysed?
Correct! Gluteus medius (and minimus) abduct the hip and stabilise the pelvis during single-leg stance. When the gluteus medius is paralysed (superior gluteal nerve palsy), it cannot hold the contralateral pelvis up → the pelvis drops on the opposite (unsupported) side when standing on the affected leg = Trendelenburg sign.
Trendelenburg sign: pelvis drops on the OPPOSITE (non-weight-bearing) side → indicates weak hip abductors on the STANDING side. Cause: superior gluteal nerve palsy (paralysing gluteus medius + minimus + tensor fasciae latae). Also seen in hip dislocation and coxa vara. Trendelenburg gait: compensatory trunk lean toward the affected side.
Incorrect. Gluteus maximus extends the hip but does not abduct it. The Trendelenburg sign is due to weakness of the hip abductors — primarily gluteus medius.
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A 70-year-old man undergoes total hip replacement using the posterior approach. The physiotherapist counsels him to avoid certain hip positions post-operatively to prevent dislocation. Which combination of movements should he most avoid?
Correct! After THR via the posterior approach, the posterior capsule and short external rotators are repaired but remain vulnerable. The prosthetic head can dislocate posteriorly if the patient places the hip in the same position that causes posterior dislocation: flexion >90° + adduction + internal rotation. Patients are counselled to avoid crossing their legs, bending forward past 90°, and internal rotation.
Post-THR posterior approach precautions (to prevent posterior dislocation): NO hip flexion >90°, NO adduction past midline, NO internal rotation. Patient instructions: do not cross legs, do not pick up objects from the floor without bending the knee first, elevated toilet seat for 3 months. Anterior approach has fewer restrictions.
Incorrect. Post-THR (posterior approach), the dangerous combination is flexion >90° + adduction + internal rotation — this is the same mechanism as posterior dislocation of the native hip.
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