Hip dislocation !
A hip dislocation is when the ball of the femur comes out of the hip socket; in a natural hip it takes major trauma and is usually backward.
Updated 2026-10-29
Structures involved
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- Hip bone
- Femur
- Hip capsule
- Sciatic nerve
- Ligament of the femoral head
- Acetabular labrum
- Circumflex femoral arteries
- Iliofemoral ligament
- Ischiofemoral ligament
- Femoral head cartilage
Why it happens
What it is
Displacement of the femoral head out of the acetabulum. In a native hip it needs high-energy trauma, and most dislocations are posterior.
Who gets it
A typical injury of young adults in traffic collisions, including motorcycle crashes. Dislocation of a hip replacement is a separate, lower-energy problem in older adults.
Causes
- Posterior: axial force on the flexed, adducted knee and hip, as when the knee hits the dashboard
- Anterior: forced abduction and external rotation
- Falls from height and sports at high speed
Risk factors
- Traffic collisions without seat belts
- Motorcycle crashes
- Previous hip replacement (prosthetic dislocation)
- Hip dysplasia
Pathophysiology
The hip is a deep, stable ball-and-socket joint, so dislocation tears the capsule and the ligament of the head of the femur and often fractures the acetabular rim or femoral head. Stretching or kinking of the retinacular vessels threatens the blood supply of the head, and the longer it stays out, the higher the risk of avascular necrosis.
Classification
- Posterior (most common), anterior or central (fracture-dislocation through the acetabulum)
- Simple or with associated fractures (acetabular wall, femoral head: Pipkin classification)
- Thompson-Epstein classification for posterior dislocations
Symptoms and signs
- Severe hip pain and inability to move the leg after trauma
- Posterior: leg shortened, flexed, adducted and internally rotated
- Anterior: leg abducted and externally rotated
- Foot drop or numbness if the sciatic nerve is injured
Diagnosis
- Clinical
- ATLS primary survey, then the position of the limb and a careful neurovascular examination before and after reduction.
- Tests
- Trauma laboratory tests as needed; none confirm the dislocation.
- Imaging
- An anteroposterior pelvic radiograph shows it; CT after reduction looks for acetabular or femoral head fractures and loose fragments in the joint.
Differential diagnosis
- Femoral neck fracture
- Intertrochanteric fracture
- Acetabular fracture
- Femoral shaft fracture
- Dislocated hip replacement
Goal of treatment
Reduce the hip as an emergency, ideally within about 6 hours, to protect the femoral head blood supply and the sciatic nerve, then restore a stable, congruent joint.
Treatment
- Acute
- Emergency closed reduction under sedation or anaesthesia, using traction techniques (such as Allis), followed by imaging.
- Surgical
- Open reduction if closed reduction fails, the joint is not congruent or a fragment is trapped.
- Surgical
- Fixation of associated acetabular or femoral head fractures.
- Follow-up
- Repeat neurovascular checks and follow-up for avascular necrosis.
- Rehabilitation
- Protected weight-bearing and physiotherapy for strength and range of motion.
Complications
- Avascular necrosis of the femoral head
- Sciatic nerve injury
- Post-traumatic osteoarthritis
- Recurrent dislocation
- Heterotopic ossification
- Deep vein thrombosis
Prognosis
Simple dislocations reduced early often do well. Late reduction, associated fractures and nerve injury raise the risk of avascular necrosis, arthritis and lasting disability.
Prevention
- Seat belts and road safety measures
- Following hip precautions after hip replacement
Test yourself
Think of the answer, then tap the question to see it.
What is the most common direction of traumatic hip dislocation?
Posterior, typically from a dashboard injury with the hip and knee flexed.
What is the classic limb position in a posterior hip dislocation?
Shortened, flexed, adducted and internally rotated.
Which nerve is most often injured in a posterior hip dislocation?
The sciatic nerve, mainly its fibular division, causing foot drop.
Why is a hip dislocation an orthopaedic emergency?
The longer the head stays out, the greater the risk of avascular necrosis; reduction within about 6 hours is the aim.
Which knee injuries go with a dashboard hip dislocation?
Patellar fracture and posterior cruciate ligament injury, so the knee must be examined.
Related conditions
- Avascular necrosis of the femoral head
- Femoral shaft fracture
- Femoral Neck Fracture
- Hip Osteoarthritis
- PCL Injury
- Patellar fracture
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Posterior Hip Dislocation (StatPearls (NCBI Bookshelf), 2023).
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