Joint capsule; Articular capsule - Capsula articularis
The articular capsules form complete envelopes for the freely movable joints. Each capsule consists of two strata—an external (stratum fibrosum) composed of white fibrous tissue, and an internal (stratum synoviale) which is a secreting layer, and is usually described separately as the synovial membrane.
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).
General Anatomy > Joints; Articular system > Bony joints > Synovial joint; Diarthrosis > Joint capsule; Articular capsule