Myotendinøse

Myotendinøse or myotendinous junctions (MTJ) are the regions where skeletal muscle fibers attach to tendons, forming the interface through which contractile force is transmitted from muscle to bone. In this junction, muscle fibers interdigitate with the tendon matrix, creating a large interface area that helps distribute mechanical stress and reduce strain concentrations.

Structurally, the MTJ features folding and protrusions of the muscle cell membrane into the tendon’s extracellular matrix, increasing surface area. The tendon is rich in type I collagen and organized collagen fibrils, while the muscle side contains a specialized cytoskeleton and basement membrane components. The gradient in tissue stiffness and the interlocking architecture enhance secure force transfer and resist injury during rapid or high-load contractions.

Functionally, the MTJ serves as the critical link between muscle contraction and tendon transmission of force to bone. It is a dynamic structure that remodels in response to loading, with increased interface complexity and strength occurring with regular eccentric and resistance training. Aging, overuse, or inadequate conditioning can compromise MTJ integrity, making it more susceptible to strain or tear.

Injury to the MTJ is common in athletes, often during high-speed or eccentric activities. MTJ injuries include partial or complete tears at the muscle-tendon interface, frequently affecting the hamstrings, gastrocnemius, quadriceps, or adductors. Clinical presentation includes sudden focal pain near the MTJ with functional loss. Diagnosis relies on clinical assessment supported by imaging, especially magnetic resonance imaging (MRI) and ultrasound, which can show edema and disruption at the junction. Management ranges from rest and rehabilitation to, in some cases, surgical repair, with prognosis depending on injury severity and rehabilitation quality. Prevention emphasizes progressive loading, eccentric strengthening, and adequate recovery.