# Hip Dislocation

> Hip dislocation for NEET-PG Orthopaedics: posterior dashboard injury, limb posture, sciatic nerve risk, urgent reduction and AVN prevention, exam points.

- Canonical URL: https://prepelephant.com/topics/neet-pg/orthopaedics/hip-dislocation
- Exam / course: NEET-PG · Subject: Orthopaedics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Hip Dislocation", PrepElephant, https://prepelephant.com/topics/neet-pg/orthopaedics/hip-dislocation

## Direct answer

Traumatic hip dislocation is a high-energy injury — the classic dashboard strike on a flexed knee driving the head backwards out of the acetabulum. The posterior dislocation, by far the commonest, holds the limb flexed, adducted and internally rotated with apparent shortening, and threatens the sciatic nerve. Reduction is an emergency performed as soon as the patient is resuscitated, because every hour the head stays out raises the risk of avascular necrosis of the femoral head; post-reduction CT checks congruency and hidden fractures.

## What you must remember

- **Posterior dislocation dominates:** a dashboard or fall on the flexed, adducted hip drives the head posteriorly; the limb lies flexed, adducted, internally rotated and shortened, and the greater trochanter feels prominent.
- **Sciatic nerve at risk:** injured or stretched in posterior dislocations — check foot dorsiflexion and plantarflexion and sensation before and after reduction; the peroneal division suffers first, presenting as foot drop.
- **Anterior dislocation** follows forced abduction-external rotation; the limb lies abducted, flexed and externally rotated, and the femoral nerve or vessels may be injured; an obturator variant points the limb adducted with medial thigh pain.
- **Emergency reduction:** after ATLS resuscitation, closed reduction under anaesthesia with muscle relaxation — urgently, since delay feeds avascular necrosis of the head by strangulating its retinacular blood supply.
- **Post-reduction imaging:** repeat radiographs for joint congruence, then CT to exclude an intra-articular loose body, posterior wall fracture of the acetabulum, or a Pipkin fracture of the femoral head.
- **Central fracture-dislocation:** the head is driven medially through the acetabular floor into the pelvis — internal bleeding and visceral injury dominate, and the hip joint itself is usually destroyed.
- **Aftercare and prognosis:** bed rest with restricted positioning avoiding flexion-adduction-internal rotation, protected weight-bearing, and follow-up imaging for avascular necrosis, which may declare itself months later.

## Common confusion

The limb postures are swapped in a hurry: posterior dislocation internally rotates and adducts, anterior externally rotates and abducts — the limb follows the head. The second confusion is hip dislocation versus femoral neck fracture in the elderly: both shorten and externally rotate the limb, but the dislocation follows major trauma in a younger patient with the hip markedly flexed and adducted. And a hip that fails to stay congruent after reduction is a CT problem — a trapped fragment or fractured wall needs surgery, not repeat closed attempts.

## Exam-focused takeaway

NEET-PG frames hip dislocation around mechanism, posture and urgency: a dashboard injury with a flexed, adducted, internally rotated limb is the posterior pattern, and the question chain asks for the nerve at risk (sciatic) and the timing of reduction (emergency, after resuscitation). Anterior-pattern stems describe forced abduction with an externally rotated limb. Avascular necrosis appears as both a delay question and a late-complication vignette, image stems show the head dislocated posteriorly or driven medially into the pelvis, and post-reduction stems ask why CT is done.

## Frequently asked questions

### Which hip dislocation is commonest and how does the limb lie?

Posterior dislocation from a dashboard injury, with the limb flexed, adducted, internally rotated and apparently shortened.

### Which nerve is most often injured in posterior hip dislocation?

The sciatic nerve, particularly its peroneal division, so foot movement and sensation must be documented before and after reduction.

### Why must a dislocated hip be reduced urgently?

Delay strangulates the retinacular blood supply of the femoral head, sharply increasing the risk of avascular necrosis; reduction is a time-critical emergency.

### What imaging follows successful reduction?

Repeat radiographs for congruence and a CT scan to exclude intra-articular fragments, acetabular wall fractures and femoral head fractures.

### What is a central dislocation of the hip?

Medial displacement of the femoral head through a fractured acetabular wall into the pelvis, a high-energy injury with dangerous internal bleeding and a poor prognosis for the joint.