Approach to limping child

Differential diagnoses:

0 to 5 years old

• Septic arthritis
• Osteomyelitis
• Transient hip synovitis
• DDH
• Perthes disease
• Toddler's fracture
• Nonaccidental injury (child abuse)
• Tumors (ALL)
• Neuromuscular disorders (cerebral palsy, Duchenne's Muscular Dystrophy)
• Discitis
• Juvenile rheumatoid arthritis

5 to 10 years old

• Septic arthritis
• Osteomyelitis
• Transient synovitis
• Perthes
• Limb length difference
• Tumor (ALL, Ewing sarcoma, benign bone tumors)
• Neurologic disorders (hereditary motor sensory neuropathy)
• Discitis
• Juvenile rheumatoid arthritis

10 to 15 years old

• Osteomyelitis
• Slipped capital femoral epiphysis (SCFE)
• Tumor (osteosarcoma, Ewing's sarcoma, benign bone tumors)
• Perthes disease
• Hip dysplasia
• Idiopathic chondrolysis

History

• Acuteness of onset, pain, history of trauma or injury, constitutional symptoms such as fever, malaise, chills; early morning stiffness and motor milestone development (walked by 15-18 months).
• Past medical history, Birth history and any previous surgery, injuries, or illnesses.
• Family history of childhood lower extremity conditions such as developmental dysplasia of the hip (DDH).

Physical examination

• An antalgic gait is characterized by a decreased stance period on the affected limb as well as a trunk shift over the affected limb during stance.
• Evaluation for limb length difference: palpate the anterior superior iliac spine (ASIS) with the patient standing. Then, with the patient supine, compare lengths of the lower extremities with the legs extended. Also, compare lengths of the femurs by flexing the hips and comparing the relative heights of the knees.
• Physical exam should also include the back, sacroiliac (SI) joints, and abdomen as well as the entire extremity involved.
• Palpate the entire length of the limb.
• Range of motion of the hip, knee, and ankle joints. Particular attention should be paid to any erythema, warmth, joint effusion, or focal tenderness.
• A thorough neurologic examination should also be completed.

Investigation 

• Radiographic evaluation. Anteroposterior (AP) and lateral plain radiograph (x-ray) of the entire length of bone involved, including joint above and below the area of concern. Referred pain describes pain attributed to one site or location by the patient but the source of the pain is at a different site (e.g., knee pain in a patient with an SCFE involving the hip joint). 
• Laboratory studies. Complete blood count (CBC) with differential, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). If rheumatologic conditions or spondyloarthropathies are being evaluated, include rheumatoid factor (RF), antinuclear antibody (ANA), anti-streptolysin (ASO) titer, Lyme titer, and HLA B-27.
• Additional imaging studies.
• Magnetic resonance imaging (MRI). Very sensitive and specific. Able to identify areas of bone marrow edema, soft tissue edema, or fluid collections such as abscesses.
• Ultrasound. Useful to look for hip joint effusions, subperiosteal or soft-tissue abscesses. May also help guide aspiration of hip joint or soft tissue abscess.
• CAUTION: If septic arthritis is suspected, a joint aspiration should be performed without wasting time waiting for the availability of other additional imaging studies.