Tendons have a limited blood supply when compared with muscle,28 and are susceptible to injury when muscles remain contracted for long periods, effectively rendering the tendon avascular. This leads to the generation of destructive free radicals on reperfusion. Tendons undergo- ing repetitive use may experience a rise in temperature of up to 10%, which can lead to hyperthermic injuries. Another theory is that injury to the tendon activates protein kinases, which lead to apoptosis.29 Further theories are still being investigated, which include altered gene expression and an imbalance of matrix metalloproteinases and growth fac- tors.30 A greater understanding of these mechanisms has the potential for guiding future interventions.
Although it is known that the structure of the affected tendon in lateral epicondylitis is degenerate with multiple micro-tears, in itself that is not sufficient to explain the var- iability in patients’ symptoms. The cause of pain in lateral epicondylitis is thought to be due in part to an increased