According to the shape and the movement, the synovial joints are of six types:
(i) Gliding Joint: The articular surface of this joint are usually flat, permitting only back and forth and side to side movements. No rotation or twisting is possible because bones are tightly packed. e.g., joints between carpal and tarsal bones.
(ii) Hinge joint: In this, the surface of one bone fits into the concave surface of another bone. e.g., joints in elbow, knee, ankle etc.
(iii) Pivot joint: A pivot joint is a joint that allows movement in only one plane. In this rounded bone fits into a shallow depression of another bone. Ex. Joint between atlas and axis, radius and ulna.
(iv) Saddle joint: It allows the movement in two planes freely. The projection of one bone fits in saddle shaped depression of another bone. e.g., the joint between the carpal and metacarpal of thumb of hand.
(v) Ball and socket joint: This is the most freely movable joint. In this, a ball like structure on the one bone fits into socket like structure in another bone. e.g., shoulder and hip joints.
