Tendon the presence of denatured collagen are factors that are believed to cause weakening of the tendon ECM and an increase in the potential for another rupture to occur. In response to repeated mechanical loading or injury, cytokines may be released by tenocytes and can induce the release of MMPs, causing degradation of the ECM and leading to recurring injury and chronic tendinopathies. A variety of other molecules are involved in tendon repair and regeneration. There are five growth factors that have been shown to be significantly upregulated and active during tendon healing: insulin-like growth factor 1 (IGF-I), platelet-derived growth factor
Achilles tendon rupture can also contribute to injury. Fluoroquinolone antibiotics, famously ciprofloxacin, are known to increase the risk of tendon rupture, particularly Achilles. People who commonly fall victim to Achilles rupture or tear include recreational athletes, people of old age, individuals with previous Achilles tendon tears or ruptures, previous tendon injections or quinolone use, extreme changes in training intensity or activity level, and participation in a new activity. Most cases of Achilles tendon rupture are traumatic sports injuries. The average age of patients is 29–40 years with a male-to-female ratio of nearly 20:1. Direct steroid injections into the tendon have also been linked