These are TWO types of osteoarthritis:
Primary Osteoarthritis is mostly related to aging. As we age, repetitive use if the joints leads to wear and tear of the cartilage. The cartilage begins to flake setting off an inflammatory reaction causing pain. Loss of the cartilage cushion causes friction between the bone and eventual loss of the joint space. Osteoarthritis is commonly found in multiple members of the same family implying a heredity or genetic factor.
Secondary arthritis is caused by another disease or condition. Obesity is the primary cause of secondary arthritis increasing load forces will cause any joint to deteriorate and eventually fail. Each extra pound overweight causes an added four-pound per square inch of force to the knee joint.
Another cause of secondary arthritis is repeated trauma to the joint. Football players who run and take repeated blows to the knees would be an example of a class of individuals with repeated trauma but this is not limited to the sports related activity. Chronic job related kneeling, kicking, jumping, or knee stress would also qualify for related trauma. Multiple surgeries is also repeated trauma. Abnormally formed joints from birth would also be prone to the development of secondary osteoarthritis. Diabetes and growth disorders are causes of cartilage wear and osteoarthritis these deposits are uric acid and calcium pyropitosphate, the etiology of gout and pseudo gout.
There are several other minor causes of secondary osteoarthritis.