Joints are the area where two or more bones meet. Here, bone is surrounded by a type of connective tissue called articular cartilage, which helps to reduce the friction on the bone created by movement. A tissue called the synovial membrane, or synovium, lines the joint and seals it into a joint capsule. The synovial membrane secretes synovial fluid (a clear, sticky fluid) around the joint to lubricate it. The joint capsule is surrounded by ligaments and tendons (other types of connective tissue) that connect to muscle and control movement of the joint.
Arthritis is a general term that refers to inflammation in joints. There are over 100 different forms of arthritis that can occur in men and women of all ages, affecting different parts of the joint. Some forms are the result of injury, disease or infection, and the inflammation goes away upon resolution of the underlying problem. However, in some injuries and diseases, the inflammation does not go away and the symptoms can worsen, indicative of chronic arthritis.