Aging

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  Natural aging processes affect the tissues and cartilage around bones as well as the bones themselves, making joints more brittle and sensitive to friction.
  
  

Trauma

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  Sports injuries and falls can damage bone and tissue at joints.
  
  

Osteoarthritis

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  Osteoarthritis affects the cartilage around bones, allowing the bones to rub against each other at joints instead of sliding easily.
  
  

Rheumatoid Arthritis

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  Genes, hormones or environment can contribute to rheumatoid arthritis, a painful disease that affects every joint in the body and causes loss of function---like some other forms, may go into periodic remission.
  
  

Gout

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  Deposits of crystallized uric acid in the joints can cause periodic inflammation and pain, usually in the feet. This condition, called gout, can be caused by poor diet.
  
  

Juvenile Rheumatoid Arthritis

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  Juvenile idiopathic arthritis (JIA) and juvenile rheumatoid arthritis (JRA) are autoimmune or autoinflammatory disorders that affect children and often go into remission with proper growth therapy.
  
  

Lyme Disease and Bacterial Infections

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  Bacterial infections can cause temporary inflammation of joints: a small number of people whose Lyme disease goes untreated will develop chronic arthritis, mainly in the knees. About half of people who contract the disease may develop transient arthritis several months after the infection.