Peritenon

Peritenon is a layer of loose connective tissue that surrounds many tendons, forming part of the soft-tissue coverings that allow movement and supply nutrients. In areas without a true synovial tendon sheath, the peritenon (often termed paratenon in some texts) acts as the main wrapping around the tendon. The term peritenon is sometimes used interchangeably with paratenon, though some sources reserve paratenon for the tissue surrounding a tendon when no synovial sheath is present, while peritenon may be used more broadly to describe the surrounding tissue around a tendon.

Anatomically, the peritenon lies outside the more fibrous epitenon, and it may fuse with the epitenon along parts of the tendon. It contains small blood vessels and nerves that provide nutrition to the tendon and serve as a conduit for inflammatory or healing processes. Its presence facilitates tendon gliding relative to surrounding tissues and can influence the spread of pathology.

Clinical relevance includes paratenonitis or peritenonitis, an inflammatory condition often related to overuse. It commonly affects tendons such as the Achilles, patellar, and hand flexors, presenting as diffuse tenderness and swelling around the tendon, especially with movement. Diagnosis is typically clinical, with confirmation by imaging modalities like ultrasound or MRI showing thickening or increased vascularity of the peritenon. Management focuses on rest, anti-inflammatory measures, physical therapy, and gradual return to activity; chronic involvement may lead to scarring and impaired tendon gliding. See also epitenon, endotenon, and tendon sheath.