15.1 Limp, Developmental Hip Dysplasia & Nursemaid's Elbow

Musculoskeletal and orthopedic problems are clinical category #8 on the PNCB CPNP-PC outline; pain is category #13 (section 15.3). Domain II wants the limp diagnosed by age, gait, and which joint is actually sick. Domain III wants the child safe tonight: Pavlik via orthopedics, a wheelchair for SCFE, the ED for a septic hip, and reduction of nursemaid's elbow as a named office procedure. You are not running a pediatric orthopedic OR. You are deciding which hip cannot wait until Monday, which elbow you reduce in the room, and which "knee sprain" is a slipped capital femoral epiphysis.

Quick Answer: Screen infant hips with Ortolani and Barlow, then Galeazzi and limited abduction. Risk: breech, family history, female. AAP imaging: ultrasound after 6 weeks when needed for risk, radiograph after 4–6 months. Pavlik is ortho-directed. Do not delay referral for an unstable hip. Kocher-like predictors (non-weight-bearing, fever, ESR/CRP, WBC) send septic hip to the ED. SCFE: obese adolescent, external rotation, referred knee pain — make the child non-weight-bearing and call ortho urgently. LCPD is younger. Nursemaid's: axial traction, held pronated/flexed; reduce with hyperpronation or supination-flexion; no x-ray if classic. Image the tibia for a toddler's fracture.

Developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) is a spectrum from capsular laxity to a frankly dislocated femoral head. Missed DDH is a lifetime of acetabular reconstruction, avascular necrosis, and early arthritis. The CPNP-PC job is a serial hip exam at well visits until the child walks well, risk-based imaging, and early orthopedic referral.

Ortolani reduces a dislocated hip: abduct and lift the femoral head into the acetabulum; a clunk of reduction is positive. Barlow asks whether a reduced hip can be dislocated: adduct and apply a gentle posterior stress; a clunk of exit is positive. These maneuvers belong to early infancy (most useful through about 2–3 months). After that, physiologic laxity falls and you will not Barlow a chronically dislocated hip back in. Later signs: Galeazzi (hips and knees flexed, feet on the table — unequal knee heights; the short femur is the dislocated side), limited abduction, and a limp or Trendelenburg once walking. Asymmetric thigh or gluteal creases are nonspecific alone. A soft "click" without a clunk is not a diagnosis.

Risk that should raise your threshold: breech presentation (especially frank breech), first-degree family history of DDH, and female sex. Tight swaddling with hips extended and adducted is a modifiable harm. Packaging deformities (torticollis, metatarsus adductus) travel with DDH. Male, vertex, no family history, normal exam: you still examine the hips at every well visit. DDH is not a one-time newborn checkbox.

AAP imaging teaching the exam expects:

• Universal physical examination, not universal ultrasound.
• Ultrasound if needed after 6 weeks for risk factors with a stable exam, or for an equivocal exam. Imaging much earlier over-calls physiologic laxity.
• Radiograph (AP pelvis) after 4–6 months, when femoral ossific nuclei make plain films readable.
• A positive Ortolani or a frankly unstable/dislocated hip is not an imaging-then-wait problem. Refer now. Do not delay referral of an unstable hip while you argue about a 4-week ultrasound slot.
• Pavlik harness is the usual infant treatment and is directed by pediatric orthopedics (fit, wear time, avascular-necrosis surveillance). Primary care does not independently harness and hope.

Clinic vignette. A 10-day-old girl born frank breech has a left Ortolani clunk. Grandmother wants "the ultrasound they do at two weeks" and a two-month follow-up. You refer today. You do not start a Pavlik yourself. You do not x-ray a 10-day-old.

The limp: septic hip versus transient synovitis

An acute limp in a young child is infection until you can defend otherwise. Septic arthritis of the hip destroys cartilage in hours. Transient synovitis is often post-viral and self-limited — a diagnosis you make after you have thought about pus in the joint.

Kocher criteria (original) and Kocher-like primary-care teaching use four predictors:

1. Non-weight-bearing
2. Fever (original Kocher used temperature >38.5°C)
3. ESR ≥40 mm/h (CRP ≥2.0 mg/dL is the common Caird/Kocher-like add)
4. WBC >12,000/µL

More predictors, higher probability of septic arthritis. A well, weight-bearing, afebrile preschooler after a URI with a mild limp and low inflammatory markers is closer to transient synovitis. A toxic, non-weight-bearing, febrile child with a high CRP is septic hip until the ED and orthopedics say otherwise. When in doubt, ED. Do not send a non-weight-bearing febrile toddler home on ibuprofen labeled synovitis.

Septic hip care after you leave the office: immediate labs, urgent ultrasound or other imaging per the receiving team, joint aspiration, surgical drainage, and antibiotics. That is not a primary-care observation trial. Osteomyelitis and pyomyositis sit on the same emergency spectrum. Lyme arthritis is a more subacute knee story in endemic areas; it does not let you ignore an acute non-weight-bearing hip.

Clinic vignette. A 4-year-old had a cold last week, now limps but walks into the room, is playful, temperature 37.4°C. That might be transient synovitis — still examine the hip, consider labs if you are not sure, and give strict return precautions. A 4-year-old who refuses all weight, is 38.9°C, and holds the hip flexed and externally rotated does not get a wait-and-see sticker. ED.

SCFE versus Legg-Calvé-Perthes

Slipped capital femoral epiphysis (SCFE) is displacement of the femoral head through the hypertrophic physis. Classic: obese adolescent (often 10–16 years), more often male, limp, hip held in external rotation, limited internal rotation, and referred pain to the thigh or KNEE. The knee exam can be bland. If you MRI the knee and miss the hip, you miss SCFE. Stable SCFE: can bear some weight. Unstable: cannot bear weight even with crutches — higher avascular necrosis risk.

Action: make the child non-weight-bearing immediately (wheelchair or stretcher, not "walk down to radiology"), urgent pediatric orthopedic evaluation, NPO pending pinning. Do not send the child to gym. Do not wait for a routine ortho slot next month. The opposite hip is at risk; orthopedics decides on contralateral pinning. Atypical SCFE (thin, very young, or short child) should make you think endocrine disease (hypothyroidism, growth hormone) — still non-weight-bearing, still urgent ortho first.

Legg-Calvé-Perthes disease (LCPD) is idiopathic avascular necrosis of the femoral head in a younger child, typically 4–8 years, more often boys, insidious limp, activity-related pain, limited abduction and internal rotation. That is not the obese 13-year-old with acute knee pain. Refer to orthopedics; management is containment and activity modification, not an office Pavlik harness.

Nursemaid's elbow — named blueprint procedure

Reduction of nursemaid's elbow (radial head subluxation) is a CPNP-PC outline office procedure. Typical age 1–4 years. Mechanism: axial traction on a pronated forearm — yanked away from a curb, swung by the hands. The annular ligament slips over the radial head. The child will not use the arm, holds it slightly flexed and pronated, and is not particularly swollen. There is no deformity.

If classic: no radiograph required. Reduce in the office.

Two acceptable reductions:

• Hyperpronation: firm hyperpronation of the forearm, often with the elbow modestly flexed. Many series find this more successful and less painful as a first attempt.
• Supination-flexion: fully supinate, then flex the elbow.

A palpable or audible click and return of use within minutes confirm success. Observe until the child reaches for a toy with that hand. If two gentle attempts fail, or if there is swelling, deformity, point bony tenderness, a fall onto the arm, or an unclear history, x-ray and stop calling it nursemaid's. Recurrence is common; teach caregivers not to lift by the hands. Chronic or irreducible cases go to orthopedics.

Do not reduce a deformed, swollen elbow and call it annular-ligament subluxation. Do not x-ray every classic case "just because." Do not send the child home in a sling for three weeks without a reduction attempt when the story is textbook.

Toddler's fracture

A toddler's fracture is a minimally displaced spiral fracture of the distal tibia in a newly walking child (about 9 months to 3 years). History is often a trivial twist or an unwitnessed limp. Exam: tibial tenderness, sometimes warmth, often little swelling. Image the tibia-fibula (AP and lateral; add an oblique if suspicion is high and the first films are normal). Treatment is immobilization (long-leg cast or walking boot per local orthopedic practice) and follow-up. In a cruising or walking toddler with a consistent story, this is a classic accidental pattern. In a non-ambulatory infant, with an inconsistent history, or with other injuries, think maltreatment (Chapter 20), not "toddlers just break."

Other cannot-miss limp items: osteomyelitis, JIA (morning stiffness — rheumatology chapter), diskitis, and malignancy (night pain and systemic signs — section 15.3). Unilateral "growing pains" are not a diagnosis.

Exam traps. Delayed referral of an Ortolani-positive hip. Ultrasound at 2 weeks for a stable-risk infant as if that replaced a 6-week study. Starting Pavlik in primary care without ortho. SCFE presenting as knee pain. Transient synovitis labeled in a non-weight-bearing febrile child. Radiograph-first nursemaid's when classic — or reducing a deformed elbow. Calling a toddler's fracture child abuse without context, or missing abuse in a non-walker.

Clinic close. Unstable newborn hip: refer today, Pavlik via ortho, US after 6 weeks for risk not as a delay tactic. Febrile non-weight-bearing hip: ED, Kocher-like labs. Obese adolescent, externally rotated hip, knee complaint: NWB, urgent SCFE pathway. Younger insidious limp: think LCPD. Yanked pronated toddler arm, no swelling: reduce with hyperpronation or supination-flexion. New walker, tibial tenderness: image the tibia.