['Blood platelets release a cocktail of growth factors when activated, some of which are thought to initiate and stimulate repair.', 'We studied whether a platelet concentrate injection would improve Achilles tendon repair in an established rat model. The Achilles tendon was transected and a 3 mm segment removed. After 6 h, a platelet concentrate was injected percutaneously into the hematoma. This increased tendon callus strength and stiffness by about 30% after 1 week, which persisted for as long as 3 weeks after the injection. At this time, the mechanical testing indicated an improvement in material characteristics--i.e., greater maturation of the tendon callus. This was confirmed by blinded histological scoring.'] Does platelet concentrate injection improve Achilles tendon repair in rats?