Structure, function and adaptation of bone-tendon and bone-ligament complexes.

Mechanical and physiological processes contribute to joint tissue adaptations during growth and exercise and after injury. Those adaptations are often in response to the mechanotransductive stimuli linked to the transmission of forces across these load-bearing structures. Muscle-tendon interactions have been explored during skeletal loading and describe the relation of sarcomere shortening at the expense of tendon lengthening(1,2). The effects of load transmission through the bone-tendon and bone-ligament complexes, however, have not been studied as extensively, although both disuse and exercise will alter the stiffness of these significant structures. Recently, however, renewed interest has emerged about the pathogenesis underlying enthesopathies and enthesitis, and investigators are beginning to reveal the intricacies of bone-tendon and bone-ligament complexes(3,4,5). Here, we summarize the structure and function of the types of entheses between bone-tendon and bone-ligament, and relate how mechanical loading leads to functional adaptation, and at times, entheseal pathophysiology.