New research into how tendons age has found that the material between tendon fiber bundles stiffens as it ages and that this is responsible for older horses being more susceptible to tendon injuries.

Researchers from Queen Mary University of London (QMUL), University of East Anglia, University College London, and University of Liverpool, all in the United Kingdom, repeatedly stretched samples of horse tendons to test their elasticity and ability to recover.

Past studies have shown that stiffening in aging tendons contributes to increased injuries in older horses, and this new research shows that it is specifically the stiffening and decreased resistance to repetitive loading of the tissue which holds tendon fiber bundles in place that is responsible.

Tendon fiber bundles are surrounded by the interfascicular matrix (IFM), which is made up of tissue which enables the fiber bundles to slide past each other and stretch independently. In horses, the superficial digital flexor tendon (SDFT), which is used to store energy for propulsion, requires greater IFM stretching than the common digital extensor tendon, which aids the positioning of the leg