The Science of Sever's Disease

Sever's disease, formally known as calcaneal apophysitis, represents an inflammatory condition of the posterior calcaneal growth plate in skeletally immature children and adolescents. The calcaneal apophysis is a secondary ossification center that appears around age 8 and typically fuses with the main body of the calcaneus between ages 14-16 years. During periods of rapid skeletal growth, the bones often grow faster than the surrounding soft tissues, creating increased tension in muscles and tendons. The Achilles tendon and plantar fascia both attach to the posterior aspect of the calcaneus, creating a traction force on the growth plate during activities involving running, jumping, or rapid direction changes. The growth plate cartilage is inherently weaker than mature bone and more susceptible to stress-related injury. Repetitive traction forces from tight posterior muscle groups, combined with impact forces from athletic activities, create microtrauma within the growth plate. This leads to localized inflammation, increased blood flow, and pain characteristic of the condition. The condition is essentially a stress reaction rather than an acute injury, developing gradually as cumulative stress exceeds the growth plate's adaptive capacity. Unlike adult tendinopathies, the problem lies within the bone itself rather than the tendon, explaining why rest is typically more effective than treatments targeting tendon pathology. The self-limiting nature of Sever's disease relates directly to skeletal maturation. As the growth plate closes and the apophysis fuses with the main calcaneal body, the weak link in the posterior heel complex is eliminated, and symptoms resolve permanently.