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Transient synovitis, Perthes disease and SUFE

Paediatrics and child health · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

RapidFull
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Suspected unstable SUFE

A pubertal young person has acute hip, thigh or knee pain and cannot walk even with crutches, with the leg resting externally rotated.

Action: Stop all weight bearing, do not force hip movement or attempt reduction, give analgesia, keep fasting if surgery is likely and contact orthopaedics immediately. Obtain bilateral AP pelvis and a safe cross-table lateral through the local radiology and orthopaedic protocol; avoid frog-leg positioning in an unstable hip.

Overview

Separate a self-limiting irritable hip from Perthes disease, slipped upper femoral epiphysis and infection, then protect the physis and femoral head through safe imaging, immediate non-weight-bearing and appropriately urgent orthopaedic care.

Transient synovitis, Perthes disease and slipped upper femoral epiphysis are age-patterned causes of paediatric hip pain, yet age alone never establishes a diagnosis. Start with the child's appearance, temperature, ability to bear weight, tempo and pain severity. Ask about recent infection, trauma, morning stiffness, night pain, weight loss, steroid treatment and endocrine or renal disease. Observe gait only when safe, then examine the spine, abdomen, groin, knee and both hips. Referred knee pain reflects shared innervation and is a recurring cause of delayed hip diagnosis.

Transient synovitis, also called irritable hip, is a temporary sterile synovial inflammation, commonly after a viral illness. The child is generally well and may still bear some weight despite a painful limp. Rotation, especially internal rotation, is limited but systemic toxicity and marked inflammatory findings are absent. It remains a working diagnosis rather than a test result: a hip effusion on ultrasound cannot distinguish sterile from infected fluid, and an early septic joint can initially look mild.

Practice

Two practice questions

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Paediatrics and child healthOriginal SBA

Stable SUFE first action

A 13-year-old with obesity has three weeks of knee pain and a new out-toeing limp. The knee examination is normal, but hip internal rotation is markedly restricted. What is the best immediate action?

Choose one answer, then submit
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Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • NHS hip pain in childrenIrritable-hip recognition, urgent symptoms and the need to exclude infection, injury and Perthes disease.
  • NHS Tayside slipped upper femoral epiphysisCurrent UK SUFE risk factors, referred knee pain, examination traps and urgent surgical referral.
  • Oxford University Hospitals Perthes diseaseUK description of vascular pathology, presentation, follow-up, containment options and long-term joint risk.
  • NHSGGC atraumatic painful limbAge-patterned differential, radiographic approach, Perthes and SUFE findings and urgent orthopaedic assessment.
  • BNF for ChildrenCurrent child-specific paracetamol and ibuprofen doses, formulations, contraindications and maximum exposure.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem ·

A clinically low-risk child with a short history can be managed with relative rest, weight bearing as comfort allows, child-appropriate analgesia and explicit return advice. Arrange review in about 48 hours to confirm improvement and again by approximately one week if symptoms have not completely resolved. Fever, increasing pain, inability to bear weight or deterioration warrants same-day reassessment. Persistence, recurrence or an atypical age should trigger imaging and reconsideration of Perthes disease, juvenile idiopathic arthritis, malignancy or infection.

Perthes disease is osteonecrosis of the developing capital femoral epiphysis caused by interruption of its blood supply. Necrotic bone is resorbed and reossified over several years; while mechanically vulnerable, the femoral head can flatten or extrude from the acetabulum. Children are typically systemically well with an insidious limp, activity-related groin, thigh or knee pain and progressive restriction of abduction and internal rotation. Symptoms can fluctuate, which must not be mistaken for durable recovery.

Initial radiographs should include the whole pelvis and both hips because disease can be bilateral and comparison is useful. Early Perthes changes may be subtle or absent; later findings include increased density, fragmentation, flattening and loss of femoral-head containment. MRI can demonstrate early perfusion and marrow change when clinical concern persists despite normal radiographs. Orthopaedic management is individualised by age, disease extent, range and containment rather than by pain alone.

Perthes care aims to preserve movement and keep the femoral head contained within the acetabulum while healing occurs. Analgesia, activity modification and physiotherapy support range, while crutches or temporary restriction may be used during painful or vulnerable phases. Selected children need casting, bracing or pelvic or femoral osteotomy. Serial clinical and radiographic follow-up is essential because deformity predicts femoroacetabular impingement and premature osteoarthritis.

SUFE is failure through the proximal femoral physis during growth. The epiphysis remains seated in the acetabulum while the metaphysis and shaft displace, producing external rotation and loss of internal rotation. Obesity and the pubertal growth spurt are common associations; hypothyroidism, growth-hormone disorders, renal osteodystrophy and other endocrinopathies are especially relevant in a young, short or underweight presentation. Disease may be chronic, acute or acute-on-chronic and can be bilateral.

Stability is clinically important. A stable slip permits some walking, sometimes only with crutches; an unstable slip does not. Unstable disease carries a much greater risk of avascular necrosis. Once suspected, stop weight bearing and movement testing that loads the physis. Bilateral AP and lateral radiography confirms most slips, but positioning must be safe: frog-leg movement is inappropriate in an unstable painful hip, for which a cross-table lateral is chosen with specialists.

Definitive SUFE care is urgent orthopaedic stabilisation, usually in-situ fixation without forceful reduction. The team assesses slip severity, stability, endocrine context and the contralateral physis. Prophylactic fixation of the opposite hip is not automatic; it is considered where bilateral risk and follow-up reliability justify surgical risk. Long-term surveillance addresses avascular necrosis, chondrolysis, further slip, leg-length difference, impingement and early osteoarthritis.

Across all three diagnoses, trajectories matter. A genuinely improving low-risk irritable hip can avoid unnecessary testing, but diagnostic labels must be withdrawn when expected recovery does not occur. Persistent or recurrent symptoms after a normal radiograph need specialist review rather than repeated reassurance. Any child who is febrile, systemically unwell or unable to bear weight requires urgent exclusion of infection, fracture and other time-critical pathology.

Key points

  • Hip disease in children commonly presents as thigh or knee pain. Examine both hips in every child with unexplained knee pain or a new out-toeing gait.
  • Transient synovitis usually affects a well, afebrile child after a viral illness, causes an acute limp with limited hip movement and should improve clearly within 48 hours and resolve over about a week.
  • Transient synovitis is a diagnosis of exclusion. Fever, systemic illness, complete non-weight-bearing, severe passive-movement pain or raised inflammatory markers require urgent assessment for septic arthritis or osteomyelitis.
  • Perthes disease is idiopathic interruption of blood supply to the capital femoral epiphysis, typically causing weeks or months of limp, activity-related groin, thigh or knee pain and loss of abduction and internal rotation in a child aged roughly 3 to 9 years.
  • Request AP pelvis and an appropriate lateral view of both hips for suspected Perthes disease; early radiographs may be normal, so persistent symptoms need orthopaedic review and sometimes MRI.
  • SUFE usually affects a peripubertal young person, especially with obesity, and causes hip, groin, thigh or isolated knee pain, limp, loss of internal rotation and obligatory external rotation during hip flexion.
  • Once SUFE is suspected, make the child strictly non-weight-bearing, provide analgesia, keep fasting if surgery is likely and obtain immediate orthopaedic advice. Do not ask them to walk for demonstration.
  • For a clinically stable SUFE, obtain bilateral AP pelvis and frog-leg lateral views according to the orthopaedic pathway. If unstable and unable to walk even with crutches, avoid frog-leg positioning and use a cross-table lateral selected with radiology and orthopaedics.
  • The standard definitive treatment for confirmed SUFE is urgent surgical stabilisation, commonly in-situ screw fixation. Forceful manipulation or attempted reduction can compromise femoral-head blood supply.
  • Review the opposite hip and growth or endocrine context. Bilateral disease is common enough to require surveillance; atypical age, low weight, short stature or endocrine features should prompt directed investigation.

Aetiology

01

Post-infectious sterile synovitis

Transient synovitis often follows a viral respiratory or gastrointestinal illness, although no single organism or mechanism is consistently demonstrated.

02

Femoral-head vascular interruption

Perthes disease arises when blood supply to the capital femoral epiphysis is interrupted for reasons that remain incompletely understood.

03

Mechanical physeal failure

SUFE develops when load across a vulnerable pubertal proximal femoral growth plate exceeds its resistance, particularly with obesity.

04

Endocrine or renal vulnerability

Hypothyroidism, growth-hormone disorders and renal osteodystrophy can weaken the physis and should be considered in atypical SUFE.

Pathophysiology

  1. 1
    Temporary synovial inflammation

    Sterile hip synovitis produces effusion, capsular distension and painful restriction without bacterial cartilage invasion or progressive bone destruction.

  2. 2
    Necrosis and reossification

    Perthes disease passes through necrosis, fragmentation, reossification and remodelling while the softened femoral head remains vulnerable to deformation.

  3. 3
    Loss of hip containment

    Lateral extrusion or flattening reduces acetabular moulding, creating progressive incongruity, restricted movement and later degenerative loading.

  4. 4
    Slip through the physis

    In SUFE the metaphysis displaces relative to the acetabular epiphysis, externally rotating the limb and mechanically blocking internal rotation.

  5. 5
    Vascular compromise after slip

    Severe or unstable displacement, and especially forceful manipulation, can injure retinacular vessels and cause femoral-head avascular necrosis.

Clinical features and red flags

Low-risk irritable hip

A well child develops acute limp after viral illness, remains partly weight bearing and has mild restriction without systemic red flags.

Perthes pattern

Weeks of intermittent limp and activity-related groin, thigh or knee pain accompany loss of hip abduction and internal rotation.

Stable SUFE

A peripubertal child with obesity walks with pain and out-toeing while hip flexion produces obligatory external rotation.

Unstable SUFERed flag

Sudden severe hip or knee pain with inability to walk even using crutches indicates instability and high avascular-necrosis risk.

Hip disease presenting at knee

A normal knee examination despite persistent knee pain should trigger bilateral hip examination and pelvic imaging.

Red flags requiring action

  • Fever, systemic illness or shock with hip pain suggests septic arthritis or osteomyelitis rather than simple transient synovitis.
  • Complete refusal or inability to bear weight requires urgent assessment even when initial radiographs are normal.
  • An unstable SUFE must not be walked, frog-leg positioned or forcibly reduced because further displacement can compromise blood supply.
  • Persistent symptoms beyond the expected transient-synovitis course require review for Perthes disease, inflammatory disease, tumour or infection.
  • Night pain, weight loss, pallor, bruising, mass or lymphadenopathy raises concern for malignancy.
  • Back pain, weakness, altered reflexes or bladder and bowel change suggests spinal infection, tumour or neurological compression.
  • Atypical SUFE in a very young, short or underweight child warrants endocrine and renal assessment.

Investigations

  1. 01
    First-line clinical risk assessmentFirst stepFirst line
    Why
    Document temperature, appearance, weight bearing, pain severity, both-hip range and infection, neurological or malignancy features.
    Interpretation and limitations
    A well partly weight-bearing child may follow an irritable-hip pathway; any red flag changes urgency and testing.
  2. 02
    First-line bilateral pelvic radiographsFirst line
    Why
    Obtain AP pelvis and an appropriate lateral view for persistent limp, restricted hip or suspected Perthes disease or SUFE.
    Interpretation and limitations
    Assess both hips for asymmetry, epiphyseal density or fragmentation and physeal displacement; normal early films do not exclude Perthes disease.
  3. 03
    Safe lateral imaging for SUFE
    Why
    Use frog-leg lateral views for stable suspected disease when the protocol permits, but cross-table lateral for an unstable painful hip.
    Interpretation and limitations
    Posteromedial physeal displacement can be visible only laterally; unsafe positioning must never be used merely to improve the image.
  4. 04
    Targeted inflammatory and blood tests
    Why
    Obtain full blood count, CRP, ESR and blood cultures when fever, severe pain, non-weight-bearing or systemic features suggest infection.
    Interpretation and limitations
    Raised values increase concern but normal early results cannot alone exclude septic arthritis or osteomyelitis.
  5. 05
    Ultrasound for effusion
    Why
    Detect hip fluid and guide aspiration when septic arthritis remains possible.
    Interpretation and limitations
    An effusion is non-specific and does not separate transient synovitis from infection without clinical and microbiological assessment.
  6. 06
    Preferred MRI for occult diseasePreferred
    Why
    Investigate persistent symptoms with normal radiographs, early Perthes disease, osteomyelitis, tumour or complex anatomy.
    Interpretation and limitations
    Marrow perfusion and structural change can appear before radiographic collapse, while infection or tumour requires a different pathway.
  7. 07
    Directed endocrine and renal profile
    Why
    Check thyroid, renal-mineral and growth-related abnormalities when SUFE occurs at atypical age, body habitus or stature.
    Interpretation and limitations
    An identified systemic disorder affects perioperative care, contralateral risk and longer-term treatment.

Differential diagnosis

01

Septic arthritis or osteomyelitis

Fever, toxicity, complete non-weight-bearing, focal bone tenderness or severe passive pain demands cultures, inflammatory tests and urgent specialist assessment.

02

Trauma and occult fracture

A toddler fracture, stress injury or undisclosed trauma may produce limp despite normal early examination or initial radiographs.

03

Juvenile idiopathic arthritis

Morning stiffness, persistent swelling, multiple joints or uveitis risk suggests inflammatory arthritis after infection has been excluded.

04

Malignancy

Night pain, weight loss, pallor, bruising, mass, lymphadenopathy or cytopenias requires urgent investigation for leukaemia or bone tumour.

05

Referred abdominal or spinal pain

Appendicitis, psoas pathology, discitis and neurological disease can alter gait while the hip itself remains structurally normal.

Additional chapter-specific clues

Infective mimicRed flag

Fever, toxicity, severe passive pain or complete non-weight-bearing makes septic arthritis the immediate priority.

Management

01Likely transient synovitisConfirm the expected recoveryFirst stepThe child is well and afebrile, can bear some weight and has a short low-risk history after viral illness.+
  1. 1Provide relative rest, age-appropriate analgesia and written advice to return immediately for fever, worsening pain or inability to bear weight.
  2. 2Review in approximately 48 hours and confirm clear functional improvement rather than relying only on reduced pain after medicine.
  3. 3If symptoms are not resolving by about one week, recur or become atypical, arrange imaging and specialist reassessment.
02Suspected Perthes diseaseImage and preserve containmentA systemically well child has persistent limp, referred knee pain or loss of abduction and internal rotation.+
  1. 1Obtain AP pelvis and suitable bilateral lateral imaging and refer to paediatric orthopaedics even if early films are equivocal.
  2. 2Use analgesia and specialist-directed activity modification or physiotherapy to preserve comfortable movement and containment.
  3. 3EscalationContinue serial clinical and radiographic review; escalate to MRI or containment surgery assessment according to age and disease extent.
03Suspected SUFEProtect the physis immediatelyA peripubertal child has hip, thigh or knee pain, out-toeing or obligatory external rotation.+
  1. 1Make strictly non-weight-bearing, give analgesia, keep fasting when appropriate and obtain emergency orthopaedic advice.
  2. 2Image both hips with AP pelvis and a stability-appropriate lateral view; avoid frog-leg positioning if the slip is unstable.
  3. 3Proceed to urgent specialist stabilisation, commonly in-situ fixation, and assess the contralateral hip and atypical endocrine risk.
04Infection concernExclude the destructive mimicThe child is febrile, unwell, completely non-weight-bearing or has severe pain on passive movement.+
  1. 1Use paediatric sepsis assessment, obtain blood cultures and inflammatory tests without delaying necessary treatment and contact orthopaedics.
  2. 2Arrange urgent ultrasound and aspiration for a suspected septic hip and MRI when bone or deep infection is possible.
  3. 3Start age-appropriate intravenous antibiotics and secure source control through the current bone-and-joint infection pathway.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Provides short-term analgesia for transient synovitis, Perthes pain or while suspected SUFE is immobilised and transferred.

Paracetamol

Use the current BNFC age- or weight-specific oral dose and maximum; prescribe a measurable paediatric formulation and review need as symptoms improve.

Check all combination products and total daily exposure, use lower or less frequent dosing where hepatic risk requires it, and do not let analgesic response override red flags.

Reduces pain and inflammatory discomfort in a low-risk irritable hip or selected Perthes care.

Ibuprofen

Use the current BNFC age- or weight-specific oral dose for a short course when an NSAID is appropriate.

Avoid with dehydration, significant renal disease, active gastrointestinal bleeding, previous NSAID hypersensitivity or NSAID-sensitive asthma; it is not treatment for septic arthritis or SUFE.

Complications

01

Missed septic joint

Prematurely labelling infection as transient synovitis can delay drainage and permit cartilage destruction, sepsis or femoral-head ischaemia.

02

Femoral-head deformation

Perthes fragmentation can heal with coxa magna, flattening or extrusion that impairs movement and joint congruity.

03

Avascular necrosis after SUFE

Unstable slip or vascular injury can collapse the femoral head and cause severe long-term pain and disability.

04

Chondrolysis and impingement

Cartilage loss or residual proximal femoral deformity can restrict movement and accelerate painful long-term femoroacetabular conflict.

05

Premature osteoarthritis

Persistent incongruity after Perthes disease or SUFE increases abnormal contact stress and may require reconstructive or replacement surgery later.

Monitoring and follow-up

  • For presumed transient synovitis, record temperature, weight bearing, hip movement and pain trajectory at planned early review.
  • Escalate immediately if fever, systemic illness, increasing pain or inability to bear weight develops at home.
  • Confirm complete resolution rather than allowing a recurrent or persistent limp to retain an irritable-hip label.
  • In Perthes disease, follow range of movement, activity pain, femoral-head shape and acetabular containment through serial specialist review.
  • After SUFE fixation, monitor wound, pain, weight-bearing instructions and radiographic stability exactly as the surgical team directs.
  • Assess both hips over time because Perthes disease and SUFE can be bilateral or sequential.
  • Screen growth, thyroid or renal-mineral features when SUFE presentation is atypical and ensure abnormal results have a named owner.
  • Track later function, leg length, impingement symptoms and radiographic avascular necrosis or chondrolysis.

Special situations

The knee can be innocent

Shared innervation means serious hip disease may present with isolated knee pain despite a completely normal knee examination.

Trajectory validates irritable hip

Clear improvement within 48 hours supports transient synovitis; non-resolution should change the diagnosis rather than prolong reassurance.

Early Perthes films can be normal

Persistent restricted hip movement warrants orthopaedic review and often MRI even when initial pelvic radiographs appear reassuring.

SUFE stability changes positioning

A child unable to walk even with crutches should not undergo frog-leg movement; use specialist-selected cross-table imaging.

Do not reduce SUFE clinically

Forceful manipulation can injure femoral-head vessels, so stabilisation and any corrective strategy belong to paediatric orthopaedics.

Common pitfalls

  1. 01

    Diagnosing transient synovitis from an effusion without considering infection.

  2. 02

    Failing to examine the hips when the symptom is knee pain.

  3. 03

    Reassuring after normal early radiographs despite persistent limp and restricted movement.

  4. 04

    Asking a child with possible SUFE to walk or repeatedly testing painful hip range.

  5. 05

    Using frog-leg positioning for an unstable SUFE.

  6. 06

    Attempting to manipulate or reduce a slip before specialist fixation.

  7. 07

    Treating intermittent Perthes symptoms as proof that the disease has resolved.

  8. 08

    Missing endocrine or renal disease in an atypical SUFE presentation.

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