Tendon injuries

Tendons are anatomical structures connecting muscles to bones which generate transmission of forces, thereby ensuring joint movements.1 Due to overuse or age-related degeneration, tendon injuries have become a common clinical problem. Damaged tendons heal slowly and rarely retain the structural integrity and mechanical strength of a healthy tendon, which often results in clinical challenges as well as patient burden. According to clinical observations and statistical data, certain tendons are prone to a higher possibility of injury. These are the rotator cuff, forearm extensors, Achilles tendon, tibialis posterior and patellar tendons.2,3 The attachment of tendon to bone is termed an osteotendinous junction or enthesis.4,5 The attachment between muscles and the tendon is called a myotendinous junction; a highly specialised region where tendinous collagen fibrils are inserted into deep recesses formed by myocytes. This arrangement allows first, the transmission of tension generated by intracellular, muscular contractile proteins to the tendinous collagen fibres,6 and second, reduces the exerted tensile stress that is applied to the tendon.1 The enthesis reduces and dissipates stress concentration at the hard-soft tissue junction, prevents collagen fibre bending, sharing and failure.7-10 There are two types of entheses: fibrous entheses and fibrocartilaginous entheses. In a fibrous enthesis, the collagenous tendon or ligament directly attaches to the bone, whereas the fibrocartilaginous interface encompasses different transitional zones, namely, uncalcified fibrocartilage, calcified fibrocartilage and bone.