What membrane in a diarthrotic joint provides lubrication for movement?ball and socket, hinge, pivot, saddle are types

A diarthrotic joint is also known as a synovial joint.  These joints are freely movable, and include hip and shoulder joints (ball and socket), ankle and elbow joints (hinge), and the thumb (saddle).  A synovial joint cavity is lined with vascular synovial membrane, which secretes synovial fluid to lubricate the joint.