Achilles tendon rupture: a review of etiology, population, anatomy, risk factors, and injury prevention.

Sports participation has undergone an increase in recent decades. Injury due to sporting activity has also recently risen. The Achilles tendon has been one of the most common sports-related injuries. A 2 in 100,000 individual Achilles tendon injury rate increased to a 12 in 100,000 individual injury rate in less than 10 years. The injury is typically observed in men in the fourth to fifth decades of life. Male to female injury ratios range from 2:1 to 12:1. Running, jumping, and agility activities involving eccentric loading and explosive plyometric contractions are usual mechanisms. Natural aging allows predisposing chronic degeneration of the tendon. Blood flow decreases and stiffness increases with aging to decrease the ability to withstand stress. Noninflammatory tendinosis and chronic tendinopathy are 2 separate processes proposed for tendon degeneration and subsequent rupture. Rupture typically occurs 2 to 6 cm proximal to the calcaneal insertion. Predisposing factors are grouped into 2 categories: intrinsic and extrinsic risk factors. Avoidance of degenerative changes within the tendon is the primary method to prevent rupture. Regular physical activity as athletes age also promotes tendon hypertrophy, increases nutrient delivery, and reduces collagen fiber fatigue.