<P> Occasionally the fourth and fifth carpometacarpal joints have a separate synovial membrane . </P> <P> Osteoarthritis of the carpometacarpal joints is a type of joint disease that results from breakdown of joint cartilage and underlying bone . When it affects the thumb it is termed trapeziometacarpal osteoarthritis . </P> <P> Carpometacarpal bossing is the presence of a small immovable protuberance over the joint . </P>

In terms of the arthokinematics of the wrist the axis of rotation is located at which carpal bone