Arthritis literally means "inflammation of the joint" and is not actually a single disease, but, according to Medical News Today, it is a term that covers over 100 distinct medical conditions. A joint is where two bones meet, and is covered by a tough fibrous capsule and cartilage. Inside most joints is a fluid called synovial fluid that helps nourish the cartilage and joint. Some types of arthritis affect the cartilage itself, and other types attack the synovial fluid. Symptoms of arthritis include joint pain, inflammation and redness, or stiffness. There are many different causes of arthritis, but in many cases, the process is not fully understood.
Obesity
According to the Centers for Disease Control and Prevention (CDC), 66 percent of adults with doctor-diagnosed arthritis are overweight or obese. Osteoarthritis is the most common form of arthritis, according to Mayo Clinic, and is a wear-and-tear breakdown of the cartilage and joint. Extra body weight adds tremendous additional stress to the joints and can cause premature destruction of the bone surfaces. In the early stages, the smooth surface of the cartilage becomes rough and callous, and can eventually be destroyed, leaving the bone surfaces to rub on one another. While obesity may be a primary cause of osteoarthritis, it is certainly an aggravating factor in all types of arthritis.
Injury
Osteoarthritis is the result of poor joint function and improper biomechanics. Injuries, such as car accidents or sports injuries, can lead to poor function. In the case of an injury, the muscles that surround the joint may become torn, and as they go through the healing process, scar tissue is built in order to repair the torn muscle. This will limit proper motion of the joint and may cause additional stress whenever the joint is used in the future. Muscle dysfunction, muscle weakness and ligament laxity can all lead to less than adequate joint function, which will eventually result in early destruction or arthritis.
Aging
According to the National Institutes of Health, Osteoarthritis may be the result of the aging process. As the body gets older, cartilage tends to wear out, and necessary fluids dry out, leaving the joint exposed to more wear and tear. There are many things that adults can do to retard joint degeneration. Remaining active and including daily stretching and exercise helps keep joints healthy.
Genetics
The Mayo Clinic reports that doctors do not fully understand the genetic component in most forms of arthritis, specifically rheumatoid arthritis, but notes that genetics are likely a key component. With rheumatoid arthritis, the body's own immune system attacks the synovial lining of the joints, resulting in inflammation and joint destruction.
