Osteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joint
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...

s, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking
Joint locking (symptom)
In medicine, joint locking is a symptom of pathology in a joint. Joint locking is a common symptom of:*Osteochondritis dissecans*Synovial osteochondromatosis...

, and sometimes an effusion
Joint effusion
A joint effusion is the presence of increased intra-articular fluid. It may affect any joint. Commonly it involves the knee.-Differential diagnosis:There are many causes of joint effusion...

. A variety of causes—hereditary, developmental, metabolic, and mechanical—may initiate processes leading to loss of cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...