Developmental dysplasia of the hip (DDH) is a spectrum from a shallow acetabulum to a dislocated femoral head in an infant. In the UK it is found by the NIPE screening examination before 72 hours and at 6 to 8 weeks, confirmed by ultrasound, and treated early in a Pavlik harness, which is what the ST3 T&O interviewer expects you to walk through.
Key takeaways
- The NIPE handbook states that 3 to 5 per 1,000 live births may need a Pavlik harness and 1 to 2 per 1,000 may need surgery; the BSCOS consensus cites one in 1,000 newborns with a completely dislocated hip.
- NIPE national hip risk factors are a first-degree family history of early hip problems needing treatment, breech at or after 36 completed weeks (including after successful ECV), and breech at birth from 28 weeks.
- A screen-positive examination is leg length difference, knees at different levels, unilateral abduction limited by 20 degrees or more, bilateral loss of 30 degrees or more, or a clunk on Ortolani or Barlow.
- The October 2025 NIPE handbook runs the screen-positive ultrasound at 4 to 6 weeks with an outcome decision by 6 weeks of age; BSCOS 2023 asks for a scan within 2 weeks of an abnormal examination.
- BSCOS consensus: a harness is used for at least 6 weeks after the hip is centred, the alpha angle should be at least 60 degrees before removal, and a hip not centred by 3 weeks has the harness stopped.
What is developmental dysplasia of the hip and who gets it?
Developmental dysplasia of the hip is abnormal development of the acetabulum and proximal femur ranging from mild acetabular deficiency through subluxation to frank dislocation, present at birth or evolving in infancy.
According to the BSCOS consensus paper (Bone Joint J 2023), one in 1,000 newborns has a completely dislocated hip and between 2% and 3% have some degree of dysplasia.
The NIPE handbook states the incidence of babies requiring treatment is 3 to 5 per 1,000 live births for a Pavlik harness and 1 to 2 per 1,000 for surgery.
NIPE national hip risk factors for DDH are a first-degree family history of an early hip problem needing a splint, harness or operation; breech presentation at or after 36 completed weeks regardless of delivery; and breech at birth from 28 weeks.
Girls and babies with a family history carry higher risk, per the NHS patient information, and the BSCOS consensus proposed adding non-CTEV foot deformities and packaging disorders to the ultrasound triggers.
How does the NIPE screening programme detect developmental dysplasia of the hip?
NIPE detects developmental dysplasia of the hip with a clinical examination completed before or at 72 hours of age, repeated at 6 to 8 weeks in primary care, plus selective ultrasound for risk factors or an abnormal examination.
The NIPE handbook states the practitioner observes leg length symmetry, the level of the knees with hips and knees flexed, and abduction in flexion, then performs Barlow and Ortolani on each hip separately.
The Barlow manoeuvre screens for a dislocatable hip, which is displaced out of the joint by the test; the Ortolani manoeuvre screens for a dislocated hip, which is felt clunking back into place.
A screen-positive result is a leg length difference, knees at different levels, unilateral abduction limited by 20 degrees or more, gross bilateral loss of 30 degrees or more, or a palpable clunk.
The handbook is explicit that asymmetric skin creases are not part of the NIPE screen and no longer count as a positive finding.
Who needs a hip ultrasound for developmental dysplasia of the hip, and when?
A hip ultrasound for developmental dysplasia of the hip is needed for any baby with a NIPE risk factor or an abnormal examination; the handbook treats both as screen positive and sends them down one pathway.
The NIPE screen-positive pathway (updated 10 October 2025) states that a baby born at 34 weeks or more has the ultrasound between 4 and 6 weeks of age, with orthopaedic specialist review and an outcome decision by 6 weeks.
For a baby born before 34 weeks the scan is at 38 to 40 weeks corrected age, with the outcome decision by 40 weeks corrected.
However, the BSCOS consensus states that a child with an abnormal neonatal examination must have an ultrasound within 2 weeks, and records no consensus on whether such hips can wait until 4 to 6 weeks.
In practice, quote both: the national pathway's 4 to 6 week window and 6 week decision, and the BSCOS position that a clinically abnormal hip should be scanned within 2 weeks in a one-stop clinic.
A screen-positive hip at the 6 to 8 week infant check is referred directly to a paediatric orthopaedic surgeon and should be seen by 10 weeks of age, per the NIPE handbook.
How is a hip ultrasound for developmental dysplasia of the hip reported?
A hip ultrasound for developmental dysplasia of the hip is reported using the Graf method, and the BSCOS consensus asks for Graf's standard headings: age, usability, description, measurement and classification.
BSCOS states the core minimum on every scan is whether the hip is centred, the alpha angle if it is, and a sonographic dynamic test of stability.
The BSCOS flowchart discharges a centred hip with an alpha angle over 60 degrees at any age without further orthopaedic review, and treats a decentred Graf type III or IV hip.
A Graf 2a hip is immature rather than dysplastic; the NIPE handbook accepts that a rescan for immaturity will fall beyond 6 weeks of age and asks that this be recorded.
What is the initial management of developmental dysplasia of the hip?
Initial management of developmental dysplasia of the hip diagnosed in the first months is an abduction device, usually the Pavlik harness, fitted in the clinic that confirms the diagnosis so treatment starts at the scan.
The NHS patient information states the harness is worn for 6 to 12 weeks depending on severity, stays on through nappy changes and bathing, and is adjusted as the baby grows.
The BSCOS consensus states a harness should be used for at least 6 weeks after the hip is centred, that the alpha angle should be at least 60 degrees before removal, and that centred hips in a harness are seen every 2 weeks and scanned every 2 to 4 weeks.
BSCOS also states that a decentred hip which fails to centre should have the harness discontinued by 3 weeks, because persisting risks damage to the femoral head and delays the alternative.
If a femoral nerve palsy develops, the consensus allows a further attempt at the harness once the palsy has resolved.
What happens when developmental dysplasia of the hip presents late?
Developmental dysplasia of the hip that presents late is no longer a harness problem. The NIPE handbook states Barlow and Ortolani are no longer accurate after 3 months, so the signs become limited abduction, leg length difference and gait.
The BSCOS paper states that detection after early infancy requires surgery to reduce the dislocation, and that this becomes more complicated with poorer outcomes as the child ages.
The NHS information describes a rigid abduction brace when the harness fails or the child is older, and surgery with a cast for severe or failed cases; the choice between closed and open reduction, with or without osteotomy, is made by the paediatric orthopaedic team on age and imaging.
In practice the panel wants you to say that the older child is imaged with radiographs rather than ultrasound, and that a delayed diagnosis is a safeguarding-neutral but pathway-critical event to report.
What do the NIPE and BSCOS standards say about developmental dysplasia of the hip?
The NIPE standards for developmental dysplasia of the hip are that the newborn examination is completed by 72 hours (KPI NP1) and that a screen-positive baby has an outcome decision by 6 weeks of age (standard 4, KPI NP4).
The BSCOS 2023 consensus supports continuing clinical screening at birth and 6 to 8 weeks by a small group of expert examiners, advocates universal ultrasound screening, and calls for a randomised trial to compare the two.
BSCOS also states that all patients should have outcomes recorded on a national database and that every child treated in a harness needs follow-up to 2 years, or walking age, with normal radiographs.
What are the complications of developmental dysplasia of the hip and its treatment?
The complications of developmental dysplasia of the hip are late presentation needing surgery, residual dysplasia, and early osteoarthritis; the BSCOS paper states DDH is the indication for 10% of all hip replacements and 25% of those under 40.
Harness treatment carries its own risks: femoral nerve palsy, skin problems, failure to reduce, and damage to the femoral head, which is why BSCOS stops the harness at 3 weeks if the hip has not centred.
The NIPE handbook states that undetected unstable hips with delayed treatment may need complex surgery and lead to impaired mobility and pain from osteoarthritis of the hip and back.
What is the interviewer listening for on developmental dysplasia of the hip?
The interviewer is listening for the screening pathway in the right order: 72 hours, 6 to 8 weeks, the risk factors, the screen-positive signs, and the ultrasound timing with the BSCOS caveat.
They want to hear Graf reporting, the alpha angle threshold of 60 degrees from the BSCOS consensus, the harness rules, and an honest account of what happens when developmental dysplasia of the hip is missed.
A strong candidate names the NIPE handbook date and the BSCOS consensus, and says where the two differ rather than blending them.
What are the common mistakes with developmental dysplasia of the hip?
The commonest mistake with developmental dysplasia of the hip is quoting asymmetric skin creases or a clicky hip as screening criteria; NIPE has removed creases and BSCOS reached no consensus on clicks.
Others are giving a single ultrasound timing without saying whose it is, keeping a harness on a hip that has not centred, and performing Barlow and Ortolani on an infant older than 3 months and trusting the result.
Candidates also forget the follow-up: BSCOS asks for radiographic follow-up to 2 years after harness treatment, not discharge at harness removal.
How this comes up at the ST3 interview
Developmental dysplasia of the hip comes up at the ST3 T&O clinical station as a 6-week-old breech baby with a positive Ortolani, or as a limping 18-month-old with a short leg, and the panel wants the pathway either way.
The follow-ups are the risk factors, the ultrasound timing, what the scan reports, how long the harness stays on, when you abandon it, and what the older child needs instead.
orthointerview's question bank puts this into station form with model answers and AI-marked spoken practice, across 782 questions and 100 scenarios, so the screening dates are said aloud before the interview.