Tendons and ligaments are collagen rich connective tissues that link muscle to bone and bone to bone respectively. Tendon consists of densely packed bundles of fibrous collagen. It receives a relatively small blood supply in comparison to muscle and the bone and is characterised by high tensile strength and elasticity. Ligament has a similar anatomy to tendon, but collagen fibrils are fewer and more disorganised.

Exterior (left) and interior (right) tendons and ligaments of the knee joint. From Gray’s Anatomy 1918 (Bartleby Books: http://www.bartleby.com)

Tendon and ligament both have similar hierarchical structure, consisting of elements called fascicles, which are built of smaller basic tendon/ligament fibrils and fibroblasts. The main component of the basic fibril is type I collagen. Both ligaments and tendons are surrounded by a sheath of transparent material called the synovial membrane, a delicate connective tissue layer secreting synovium, a viscous lubricating fluid.