Chronic pain in the Achilles tendon

INTRODUCTION Achilles tendon disorders are a common entity in middle-aged active people. With increasing sports participation in the general population, the number of overuse injuries has increased1. Tendon disorders comprise 30 to 50% of all sports-related injuries and there is a lifetime risk of 52% in elite long-distance runners of suffering from an Achilles tendon injury2. Despite this high prevalence there is still a lack of knowledge about the aetiology and pathogenesis of these injuries. The terminology used to describe chronic tendon disorders has changed in the past few decades. For many years this condition was persistently defined as “tendinitis”, denoting an inflammation of the tendon3. Several researchers proposed abandoning this term as there were no signs of inflammation in chronic painful tendons analysed after biopsy or with microdialysis techniques. To redress this confusing terminology, the term “tendinopathy” was introduced to describe the clinical condition of pain, swelling and impaired performance. Nowadays this is the most accepted term for chronic Achilles tendon disorders. Histopathological studies showed that tendinopathy is frequently characterised by degeneration of the tendon tissue, also referred to as “tendinosis”3. The term tendinosis is based on histopathological characteristics and should only be used after histopathological confirmation4. The treatment of tendinopathy has been challenging in sports medicine and orthopaedics and it is therefore becoming a major problem in this field.