Sinews

Sinews, in anatomical terms, refer to tendons—the robust cords of dense connective tissue that attach muscles to bones or other structures. They transmit the force generated by muscle contraction to produce movement, while also helping to stabilize joints and store elastic energy during locomotion.

Tendons are composed primarily of type I collagen arranged into hierarchical fibers. They contain tendon cells called tenocytes within the extracellular matrix and are surrounded by connective tissue coverings such as the endotenon and epitenon. The vascular supply to tendons is relatively limited, especially in their deeper regions, which can influence healing after injury.

Tendons exhibit viscoelastic properties, allowing them to stretch slightly under load and recoil when the load is released. This behavior helps to smooth and optimize the transmission of muscle force and can contribute to energy efficiency during movement. The alignment of collagen fibers along the tendon’s line of pull provides high tensile strength, and some tendons have specialized pathways or pulleys that redirect forces to channels or joints.

Clinical relevance includes a range of tendon injuries, from tendinopathy—degenerative changes due to overuse or aging—to acute ruptures from sudden overload. Diagnosis often relies on clinical examination supplemented by ultrasound or magnetic resonance imaging. Treatments vary from rest, physical therapy, and eccentric strengthening to surgical repair in selected cases. Notable tendons include the Achilles, patellar, biceps, and rotator cuff tendons.

Etymology and usage: sinew is sometimes used in literature and common language to denote strength or resilience, but in modern anatomy it is synonymous with tendon.