Transient synovitis
Septic arthritis, gonococcal arthritis
Osteomyelitis
Osgood-Schlatter’s disease
Slipped capital femoral epiphysis (SCFE)
Legg-Calvé-Perthes disease (avascular necrosis of the proximal femoral head)
Fractures (e.g. stress fracture, child abuse, toddler’s fracture, etc.)
Jumper’s knee
Sever’s disease
Soft tissue trauma
Growing pains
Chondromalacia Patellae
Osteochondritis dessicans
Developmental dysplasia of the hip
Pyomyositis or viral myositis, Soft tissue abscess
Neoplasm (Benign) – Osteoblastoma; Osteoid osteoma.
Neoplasm (malignant) – Ewing sarcoma, Leukemia, Osteosarcoma, spinal cord tumor, neuroblastoma
Conversion disorder
Diskitis
Cerebral palsy
Meningitis
Muscular dystrophy
Myelomeningocele
Clubfoot
Congenitally short femur
Limb length discrepancy
Osteonecrosis from Sickle cell disease
Inflammation: Acute rheumatic fever, Juvenile rheumatoid arthritis, Reactive arthritis, Systemic lupus erythematosus
Idiopathic tight Achilles tendon
Trauma: Child abuse, Foreign body, Sprains and strains
Appendicitis
Psoas abscess
Hemarthrosis, Hemophilia
Discoid lateral meniscus
Lyme disease
**AAFP 2009 has a thorough differential diagnosis.
Further Reading
Am Fam Physician. 2009 Feb 1;79(3):215-224. https://www.aafp.org/afp/2009/0201/p215.html