Tendinopathy: Why the Difference Between Tendinitis and Tendinosis Matters

E d U c a t i o N Think tendinitis and you think pain and burning in the affected area, decreased strength and flexibility, and pain caused by everyday activities. As it turns out, tendinosis is far more often responsible for these symptoms than tendinitis (1,2,3). It is important for health care practitioners to distinguish between these disorders in order to apply the most appropriate treatment. Tendinitis is the inflammation of the tendon and results from micro-tears that happen when the muscu-lotendinous unit is acutely overloaded with a tensile force that is too heavy and/or too sudden. Tendinitis is still a very common diagnosis, though research increasingly documents that what is thought to be tendinitis is usually tendinosis (1,2,3,4,5). Tendinosis is a degeneration of the tendon's col-lagen in response to chronic overuse; when overuse is continued without giving the tendon time to heal and rest, such as with repetitive strain injury, tendinosis results. even tiny movements, such as clicking a mouse, can cause tendinosis, when done repeatedly. The confusion about the difference between ten-dinitis and tendinosis is widespread. Many injuries commonly presumed to be tendinitis are actually tendinosis. For example, tennis elbow is usually described as tendinitis of extensor carpi radialis brevis; however, " signs of either acute or chronic inflammation have not been found in any surgical pathologic specimens in patients with clinically diagnosed lateral tennis elbow syndrome, " proving that tennis elbow is not tendinitis (4). The histology of tennis elbow shows that it is actually tendinosis (5). A microscopic view of tendinosis reveals an increase of immature type III collagen fibers (mature type I fibers dominate in healthy tendon tissue); loss of collagen continuity so that collagen fibers are no longer aligned with each other and sometimes fail to link together to facilitate load-bearing; an increase in ground substance (the material between the body's cells); and a haphazard increase of vascularization (2,3,5). These vascular structures " do not function as blood vessels " and " are not associated with increased healing (2). " The appearance of the tendon shifts from a reflective, " white, glistening and firm " surface to a " dull-appearing, slightly brown and soft " surface (mucoid degeneration) (2,3). These changes result in a loss of strength in the tendon and increase the bulk of the tendon, both of which contribute to the cycle of injury and can set the stage for secondary …