Observed Station · Limp & Gait Disorders · Data Interpretation
⏱️ TIME REMAINING
08:00
📋 Data Interpretation Station
Limp & Gait Disorders – Clinical Scenarios with Lab & Imaging
You will be presented with 8 clinical scenarios of children with limping or gait abnormalities.
For each, interpret the clinical and laboratory data and provide: 1) Diagnosis, 2) Any other test, 3) What to do next, 4) Follow-up plan.
Septic arthritis: fever, ↑ESR, ↑CRP, joint effusionSCFE: obesity, limited IR, frog-leg X-rayPerthes: age 4-8, limited abduction, femoral head flatteningTransient synovitis: post-viral, self-limited, normal labs
Case 1
A 4-year-old boy with fever (39.5°C), refusal to bear weight on left leg, and left hip pain. Holding left hip in flexion and external rotation.
WBC
18,000/µL (elevated, normal 5-15)
ESR
65 mm/hr (elevated, normal <20)
CRP
12 mg/dL (elevated, normal <0.5)
Blood Culture
Pending
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Septic arthritis of the left hip – fever, non-weight-bearing, elevated WBC/ESR/CRP, large effusion. Kocher criteria: 4/4 (fever >38.5, non-weight-bearing, ESR >40, WBC >12,000) → 99% probability.
• Any other test: Hip Ultrasound for joint effusion, Hip aspiration (synovial fluid: WBC >50,000, Gram stain, culture, PCR for Kingella kingae), MRI (if osteomyelitis suspected).
• What to do next: Urgent orthopedic consultation. Arthrocentesis for diagnosis and surgical irrigation (arthrotomy/arthroscopy). Start IV antibiotics (vancomycin + ceftriaxone) after cultures.
• Follow-up plan: Monitor CRP (should decrease >50% in 48-72h). Repeat blood cultures. IV antibiotics for 10-14 days (uncomplicated). Clinical improvement within 48h. Watch for avascular necrosis of femoral head.
Case 2
A 13-year-old obese boy (BMI 32) with right knee pain and limp for 2 weeks. Pain is worse with walking. No fever.
WBC
7.0 × 10³/µL (normal)
ESR
12 mm/hr (normal)
CRP
0.2 mg/dL (normal)
X-ray (AP pelvis)
Normal
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Slipped Capital Femoral Epiphysis (SCFE) – obese adolescent, referred knee pain, frog-leg lateral X-ray showing posterior displacement (Klein's line does not intersect epiphysis).
• Any other test: Frog-leg Lateral View for Klein's line sign, Radiograph of contralateral hip (20-40% bilateral). Thyroid panel (hypothyroidism), renal function (if suspected secondary).
• What to do next: Admit for non-weight-bearing. Urgent orthopedic referral. In situ pinning (single screw) to prevent further slip and avascular necrosis.
• Follow-up plan: Monitor for contralateral slip (20-40% risk). Post-operative weight-bearing restrictions. Long-term: monitor for avascular necrosis, chondrolysis. Avoid high-impact activities until healed.
Case 3
A 6-year-old boy with painless limp for 3 months. Limited hip abduction and internal rotation. No fever, no trauma.
WBC
6.0 × 10³/µL (normal)
ESR
18 mm/hr (normal)
CRP
0.3 mg/dL (normal)
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Legg-Calvé-Perthes disease (LCPD) – avascular necrosis of femoral head, age 4-8, male predominance, insidious limp, normal inflammatory markers.
• Any other test: X-ray (AP & Frog-leg) for Flattening and sclerosis of the femoral head (Coxa plana), MRI (early diagnosis, assess extent of necrosis), bone age (for prognosis), Herring lateral pillar classification on X-ray to guide treatment.
• What to do next: Orthopedic referral. Containment treatment: bracing (Petrie cast, abduction orthosis) or femoral varus osteotomy if lateral pillar collapse (group B/C).
• Follow-up plan: Monitor with serial X-rays (fragmentation → reossification → remodeling). Prognosis: better if age <6 and group A (lateral pillar >50%). Physical therapy for hip range of motion.
Case 4
A 5-year-old boy with acute limp and right hip pain after a viral URI 1 week ago. Afebrile, able to bear weight with limp.
WBC
8.0 × 10³/µL (normal)
ESR
22 mm/hr (mildly elevated)
CRP
0.6 mg/dL (normal)
X-ray
Normal
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Transient synovitis (toxic synovitis) – most common non-traumatic cause of limp in children 3-8 years. Post-viral, self-limited. Normal/low-grade inflammatory markers.
• Any other test: Hip Ultrasound for Small joint effusion , if Kocher criteria low (0-1 criteria). If fever develops, worsening symptoms → repeat ultrasound, consider aspiration to rule out septic arthritis.
• What to do next: Supportive care: rest, NSAIDs (ibuprofen). Activity restriction until pain resolves. Observe clinically; resolve in 5-7 days.
• Follow-up plan: Reassure parents. If limp persists >10 days, symptoms worsen, or fever develops → re-evaluate with imaging and labs.
Case 5
A 7-year-old boy with fever (38.8°C), refusal to bear weight on left leg, and point tenderness over the distal femur. No joint swelling.
WBC
14,000/µL (elevated)
ESR
78 mm/hr (elevated)
CRP
8.5 mg/dL (elevated)
X-ray
Normal
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Acute osteomyelitis of distal femur – fever, point tenderness, elevated inflammatory markers, MRI evidence of bone marrow edema (gold standard). X-ray normal (early).
• Any other test: MRI (STIR) for Bone marrow edema in distal femur metaphysis, Blood cultures, CRP (monitor response), consider bone aspiration for culture if no source identified.
• What to do next: IV antibiotics (empiric: vancomycin + ceftriaxone if MRSA risk; cefazolin if low MRSA). Duration: 3-4 weeks total (switch to oral after clinical improvement, CRP decreasing >50%).
• Follow-up plan: Monitor CRP weekly; should decrease >50% in 7-10 days. If no improvement in 48-72h → repeat MRI for abscess. Consider surgical drainage if abscess. Follow-up for growth disturbance (physeal involvement).
Case 6
A 6-month-old infant with asymmetric thigh folds and limited hip abduction on the left. No fever, no pain.
WBC
6.5 × 10³/µL (normal)
ESR
10 mm/hr (normal)
CRP
0.1 mg/dL (normal)
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Developmental Dysplasia of the Hip (DDH) – asymmetric thigh folds, limited abduction, abnormal hip ultrasound (alpha angle <60°).
• Any other test: Pelvic X-ray (after 4-6 months for ossific nucleus), Hip Ultrasound (Graf) for Alpha angle 52° (normal >60°), beta angle 60° (normal <55°) – dysplastic hip, Ortolani/Barlow maneuvers (if still unstable).
• What to do next: Pavlik harness (for infants <6 months) – maintain hips in 90-100° flexion and neutral abduction. Full-time wear for 6 weeks, then wean. Follow-up ultrasound weekly.
• Follow-up plan: Monitor with ultrasound every 1-2 weeks to confirm concentric reduction. If no reduction after 3-4 weeks → consider closed reduction and spica cast. Long-term: monitor for residual acetabular dysplasia.
Case 7
A 5-year-old boy with limp, bone pain (especially at night), pallor, and bruising. He has had fevers on and off for 2 weeks.
WBC
45,000/µL (elevated, blasts present)
Hemoglobin
7.2 g/dL (low, normal 10.5-13.5)
Platelets
30,000/µL (low)
ESR
85 mm/hr (elevated)
X-ray
Multiple lytic lesions in long bones
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Acute Lymphoblastic Leukemia (ALL) – bone pain (night pain), pallor, cytopenias (anemia, thrombocytopenia), blasts on peripheral smear, lytic lesions on X-ray.
• Any other test: Bone marrow aspiration/biopsy (confirm diagnosis, immunophenotyping, cytogenetics). Lumbar puncture (CNS involvement).
• What to do next: Urgent oncology referral. Initiate chemotherapy per protocol. Supportive care: transfusions (RBC, platelets), antibiotics for infections.
• Follow-up plan: Monitor for tumor lysis syndrome, infections. Chemotherapy phases: induction, consolidation, maintenance. Long-term monitoring for relapse, secondary malignancies, growth/endocrine effects.
Case 8
A 10-year-old boy with acute limp and swollen right knee. He had diarrhea 2 weeks ago.
WBC
10.0 × 10³/µL (normal)
ESR
45 mm/hr (elevated)
CRP
3.5 mg/dL (elevated)
Stool Culture
Campylobacter positive
1️⃣ Diagnosis: (Write your answer below)
2️⃣ Any other test: (Write your answer below)
3️⃣ What to do next: (Write your answer below)
4️⃣ Follow-up plan: (Write your answer below)
✅ Model Answer:
• Diagnosis: Reactive arthritis (Reiter syndrome) – post-enteric (Campylobacter), asymmetric arthritis, conjunctivitis, urethritis. HLA-B27 positive.
• Any other test: HLA-B27 is Positive, Synovial fluid analysis (exclude septic arthritis), Chlamydia testing (if sexually active), HIV/hepatitis screen.
• What to do next: NSAIDs (ibuprofen/naproxen) for arthritis. Treat underlying infection (Campylobacter usually self-limited). If severe or chronic, consider sulfasalazine or TNF inhibitor.
• Follow-up plan: Monitor for persistent arthritis (>6 months) → may evolve into enthesitis-related arthritis (ERA). Treat conjunctivitis with topical steroids if severe. Resolves in weeks to months. Screen for uveitis.
⚠️ Key Concept: Approach to Limp in Children
• Septic arthritis: Kocher criteria (fever >38.5, non-weight-bearing, ESR >40, WBC >12,000). 4/4 = 99% probability → urgent aspiration.
• SCFE: Obese adolescent, knee pain, limited internal rotation → frog-leg lateral X-ray.
• Perthes: Age 4-8, painless limp, limited abduction → X-ray shows flattening.
• Transient synovitis: Post-viral, self-limited, normal labs.
• Osteomyelitis: Fever, point tenderness, MRI best imaging.
• Leukemia: Night pain, cytopenias, blasts on smear.
• Reactive arthritis: Post-infectious, HLA-B27 associated.
🎯 Examiner Scoring Checklist
• Identifies septic arthritis (Kocher criteria, hip effusion, aspiration)