Arthritis is a medical term that implies inflammation of joint(s).

Causes of this illness are diverse and involve many pathological mechanisms. The causes of arthritis are either infective or non-infective. However, whatever the cause is, it leads to pain, tenderness and limitation of movements of the affected joint(s) in most cases.

Infective causes of arthritis are numerous and include viral, bacterial, fungal and parasitic causes. Hepatitis A virus, Hepatitis B virus, Hepatitis C, Alphaviruses, Rubella virus, Retroviruses, Epstein-Barr virus, Varicella-zoster virus and Mumps virus are recognizable causes of arthritis. Bacterial arthritis is sometimes termed septic arthritis and is usually caused by Staphylococcus aureus and Streptococci. Septic arthritis is usually caused by spread of infection from nearby bones (osteomyelitis). Bacterial arthritis is rather common in the pediatric age group. Fungal causes of arthritis usually affect immune-compromised individuals like HIV infected patients. Lyme disease is one of the recognizable infective causes of arthritis in America.

Non-infective causes of arthritis are numerous and are related to many pathological mechanisms. Gouty arthritis occurs due to accumulation of uric acid in the body which might be caused by faulty diet habits or congenital metabolic abnormalities. Rheumatologic causes are numerous and lead to inflammation of the joints due to autoimmune related mechanisms. Systemic lupus erythematosus, rheumatoid arthritis, rheumatic fever, ankylosing spondylitis and reactive arthritis are amongst the commonest causes of rheumatologic inflammation of joints. Rheumatologic arthritis is commonly accompanied by other systemic manifestations such as fever, skin rash, eye inflammation, nephritis and inflammation of the blood vessels (vasculitis).

Osteoarthritis is one of the types of arthritis that are related to aging. Osteoarthritis often affects people beyond the age of 50 years and commonly affects the knees. Other rather uncommon causes of arthritis include leukemia, bone tumors and amyloidosis.

Whatever the cause of arthritis is, arthritis should be differentiated from isolated pain of the joints (arthralgia). Arthritis leads to arthralgia, but is also often accompanied by swelling, hotness, tenderness and limitation of movement of the affected joint(s).