Tendons

About the Tendons

Tendons are tough, flexible cords or bands of dense regular connective tissue that attach muscles to bones. They are composed mainly of type I collagen fibers arranged in parallel bundles, which gives them great tensile strength, along with small amounts of elastin and specialized cells called tenocytes. When a muscle contracts, the tendon transmits the force to the bone, producing movement at a joint. Some tendons also store and release elastic energy, notably the Achilles tendon during running. Tendons have a relatively poor blood supply, which is one reason they heal slowly after injury. Many tendons pass through protective sheaths lined with synovial fluid that reduce friction. Common problems include tendinopathy from overuse, as in tennis elbow and jumper knee, inflammation of the tendon sheath, called tenosynovitis, and partial or complete ruptures, such as of the Achilles tendon or the rotator cuff. The Achilles tendon, joining the calf muscles to the heel bone, is the thickest and strongest tendon in the body.