epitenon

Epitenon is the outermost connective tissue layer that surrounds a tendon, lying external to the endotenon which encases the tendon’s individual fascicles. In many regions, the epitenon is overlain by a looser tissue layer called the paratenon, which facilitates gliding between the tendon and surrounding structures. The epitenon is a vascularized sheet rich in small arteries and nerves, and it blends with adjacent connective tissues.

Structure and contents a

The epitenon is composed of dense irregular connective tissue. It houses a network of capillaries that supply the tendon with nutrients and a sensory innervation that contributes to pain and proprioception. The layer can connect with the perimysial tissue of fascicles and with surrounding paratenon, helping to integrate the tendon within its anatomical neighborhood.

Relationship to paratenon and synovial tissue

In extrasynovial tendons, the epitenon may be separated from surrounding tissues by the paratenon, a loose connective tissue layer that permits movement and friction reduction. Some tendons also have a synovial sheath or synovial lining in regions where the tendon experiences high friction or rapid gliding, but the epitenon itself is not synovial; it often functions in concert with paratenon or synovial structures to reduce friction.

Function

The epitenon provides vascular supply to the tendon, participates in nourishment and healing, and contributes to the tendon's sensory innervation. It plays a role in reducing friction between the tendon and adjacent tissues, facilitating smooth movement during muscular activity.

Clinical relevance

Injury or inflammation involving the epitenon, such as tendinopathy or tenosynovitis, can affect tendon healing and pain. Surgical repair or rehabilitation may aim to preserve the epitenon to maintain vascular supply and promote recovery. Common tendons with notable epitenon involvement include the Achilles tendon and various hand and rotator cuff tendons.