How to diagnose a prosthetic hip dislocation

Does your patient have a dislocated hip? Learn the physical signs and tests to diagnose a prothestic hip dislocation here.
Last update19th Nov 2020

The hip is a ball-and-socket joint, where the ball is the femoral head and the socket is the acetabulum.

Figure 1. Anatomy of the hip joint.

How does a prosthetic hip dislocation happen?

Dislocation of a normal hip is pretty unusual. It takes a tremendous amount of force, usually a high-speed car accident. On the other hand, patients who have had hip replacement surgery can dislocate their artificial hips with minimal force, such as rolling out of bed, or getting out of a chair. These dislocations typically happen in the first four months after surgery, and most artificial hip dislocations are posterior.

Figure 2. Most of the prosthetic hip dislocations happen in the first four months after hip replacement surgery, and most are posterior.

How to diagnose a prosthetic hip dislocation

Physical signs of a prosthetic hip dislocation

Dislocation of the hip forces the femoral head of the prosthesis out of the acetabulum and behind it. As a result, there are four physical signs to look for:

  1. Patient’s affected leg appears shortened
  2. Leg is flexed at the knee
  3. Hip is internally rotated
  4. Hip is adducted
Figure 3. Physical signs of a prosthetic hip dislocation. The patient’s leg will appear shortened and flexed at the knee, with the hip internally rotated and adducted.

Diagnostic tests for a prosthetic hip dislocation

You can confirm the diagnosis with an x-ray. On the x-ray, the femoral head is displaced out of the socket. This is best seen in the lateral view.

Figure 4. Lateral x-ray shows the femoral head displaced out of the socket.

Excellent work! You now know the basics for diagnosing a prosthetic hip dislocation.

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Recommended reading

  • Hendey, GW and Avila, A. 2011. The Captain Morgan technique for the reduction of the dislocated hip. Ann Emerg Med58: 536–540. PMID: 21839540
  • Roberts, J. 2019. “Management of common dislocations”. In: Roberts and Hedges’ Clinical Procedures in Emergency Medicine and Acute Care. 7th edition. Philadelphia: Elsevier.  
  • Roberts, J. 2019. “Otolaryngologic procedures”. In: Roberts and Hedges’ Clinical Procedures in Emergency Medicine and Acute Care. 7th edition. Philadelphia: Elsevier.  

About the author

Siamak Moayedi, MD
Associate Professor and Director of Medical Student Education, University of Maryland and Course Director, Essential and Critical Procedures, Emergency Medicine.
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