Common Causes:

• unusual exertion or overuse, including strains or sprains
• accidental injury including fracture
• gout (especially found in the big toe)
• osteoarthritis - degenerative joint disease septic arthritis
• tendinitis
• bursitis
• infectious diseases, including
  • influenza
  • measles
  • rheumatic fever
  • Epstein-Barr viral syndrome
  • hepatitis
  • mumps
  • rubella
  • varicella
• chondromalacia patellae
• osteomyelitis