Two novel discoveries about how different types of tendons age and "refresh" themselves made by researchers from University College London in the United Kingdom help explain why aging horses are atrisk for tendon injury.

Tendons play key roles in locomotion as they are the link between muscles and bones. Tendons such as the equine superficial digital flexor tendon (SDFT) are energy-storing tendons that stretch and recoil to increase the efficiency of locomotion, whereas other tendons such as the common digital extensor tendon (CDET) are primarily positional tendons that assist in limb placement.

"The energy storing tendons are subjected to much higher stresses and strains than positional tendons, which is why tendons like the SDFT are more prone to injury and micro-damage," said lead researcher Helen Birch, BSc, BSc (Ost.), PhD, senior lecturer at the Institute of Orthopaedics and Musculoskeletal Science at University College London.

Birch and colleagues previously hypothesized that the matrix of the energy storing tendons would be turned over or “refreshed” more quickly than positional tendons to maintain a healthy anatomic structure and ultimately decrease injury