Answers written by Mr Tofunmi Oni, Consultant Orthopaedic Surgeon (MBChB BSc PGDip FRCS (Tr & Orth), GMC 7074916), who specialises in revision hip surgery and leads the weekly revision hip multidisciplinary meeting at East Kent Hospitals University NHS Foundation Trust. Figures come from the National Joint Registry, the British Hip Society and the studies listed in the sources at the end. Last reviewed October 2026.
How will I know if my hip replacement has dislocated?
A dislocation usually happens suddenly, with severe pain and often a clunk, during bending, twisting or getting up from a low seat. The leg may look shorter and turned in or out, and you normally cannot stand or move the hip. The NHS notes it can happen soon after surgery or many years later. Do not try to walk on it: call 999 or go to A&E, because the hip has to be put back under sedation or anaesthetic.
How common is dislocation after a hip replacement?
Registry studies suggest around 1 to 4 in 100 hip replacements dislocate within two years; a Danish national study measuring the true rate found 3.5%, with hospitals ranging from under 1% to over 7%. Dislocation is the second commonest reason for revision in the NJR, at around 18% of first revisions. The risk is higher after revision surgery, in older or frail patients, with damaged abductor muscles, and in people with a stiff spine or a previous spinal fusion.
How much force does it take to dislocate a hip replacement?
Less than people expect. Most dislocations happen with everyday movements that combine deep bending and twisting, such as reaching down from a low chair or rolling over in bed, particularly in the first weeks before the soft tissues have healed. A fall is not needed.
Is it normal for a hip replacement to feel unstable?
Mild apprehension in the first few weeks is common while the muscles recover. A persistent feeling that the hip might give way or pop out, clunking, or episodes of the hip slipping are not normal and should be assessed, because the causes are usually correctable and a first full dislocation makes further ones more likely.
Why does my hip replacement keep dislocating?
Recurrent dislocation is usually multifactorial: the position of the cup or stem, a small head size, weak or detached abductor muscles, leg length or offset, a stiff spine that stops the pelvis moving normally, or a previous revision. Implant wear and, occasionally, infection can also underlie instability and are checked for. The British Hip Society standard says every unstable hip should be discussed at a multidisciplinary meeting and complex or repeat cases at a regional network meeting.
What movements should I avoid with an unstable hip replacement?
Until the cause is understood, avoid the combination of deep hip bending and twisting: low chairs and sofas, bending to the floor, crossing your legs, and twisting on the planted leg. Which specific movements are risky depends on the surgical approach and the direction the hip dislocates, so your surgeon will tailor the advice. These precautions are a bridge to treatment, not a long term plan.
Can an unstable hip replacement be treated without surgery?
A first dislocation is usually treated by putting the hip back without an operation, followed by movement precautions and physiotherapy to strengthen the abductors, and many patients never dislocate again. Recurrent instability is different. The British Hip Society standard states that braces have a very limited role in the definitive management of hip instability, so repeated dislocations are assessed for cause and generally treated by revision surgery.
What is a dual mobility hip?
A dual mobility cup has a large polyethylene head that moves inside a polished metal shell, with a smaller ceramic or metal head inside that, giving a much larger effective head and a far greater range of movement before the hip can lever out. A 2024 meta analysis of eight studies and over 20,000 patients found about a 75% reduction in dislocation compared with standard bearings, with no difference in infection, fracture or patient reported outcomes. In revision cases the dislocation rate with dual mobility is around 2%. Constrained liners, which physically lock the head in, are kept as a salvage option for frail patients because they fail in other ways.
What tests are done for an unstable hip replacement?
Plain X rays of the pelvis and hip, often a CT scan to measure the exact position of the components, blood tests to exclude infection, and assessment of the abductor muscles, leg length, the spine and the other hip. Sometimes an examination under anaesthetic or a MARS MRI to look at the soft tissues is needed. The aim is to find the specific cause, because the revision is then planned to correct it.
Who should I see about an unstable hip replacement?
Start with the surgeon who did the operation, who should arrange imaging. UK standards say recurrent dislocation should be managed by a consultant with a special interest and fellowship training in hip arthroplasty and discussed at a hip revision multidisciplinary meeting, with re-revision for dislocation classed as the most complex category of revision work. You are entitled to a second opinion, and I see patients with unstable hip replacements from across Kent and Sussex, including reviewing scans from other hospitals.
Sources
National Joint Registry, 22nd Annual Report 2025. https://reports.njrcentre.org.uk
British Hip Society Surgical Standard, Revision of the Unstable Hip Arthroplasty; MDT meetings for low volume high complexity procedures. https://www.britishhipsociety.com
Revision Hip Complexity Classification. Bone & Joint Open 2022;3:423-31.
Hermansen LL et al. True cumulative incidence of hip dislocation within 2 years after primary total hip arthroplasty. Acta Orthop 2022;93:503-8.
Darrith B et al. Outcomes of dual mobility components in total hip arthroplasty: a systematic review. Bone Joint J 2018;100-B:11-19.
Dual mobility versus fixed bearing implants in primary total hip arthroplasty: meta-analysis. Cureus 2024;16:e61715.
NHS.uk, Hip replacement: complications (reviewed March 2024, updated 2025). https://www.nhs.uk/tests-and-treatments/hip-replacement/
GMC, Good medical practice (2024), paragraph 18. https://www.gmc-uk.org
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