Platelet-rich plasma for muscle injury and tendinopathy.

Platelet-rich plasma (PRP) is increasingly used in Regenerative Medicine. The concept of PRP as a natural source of signaling molecules with paracrine effects in different cells is the basis for the increased PRP application as treatment for sports injuries. PRP recapitulates the principal functions of the natural healing response in orchestrating cell proliferation, differentiation, migration, and angiogenesis. After systematically searching the literature, we identified 21 trials for PRP injections in tendinopathy: 57% were uncontrolled trials and 1 cohort study in muscle. Leukocyte-PRP was used in 91.7% of tendons, of which 65.5% received 1 single injection. Given the lack of large controlled trials, it is clear that the effectiveness of conservative L-PRP treatments is not proven. The clinical evaluation of alternative formulations can be extremely informative. Other unexplored issues include activation, redosing, and concomitant longitudinal tenotomies. Limiting factors for the acceptance of PRP are the lack of evidence of obvious clinical improvement and reimbursement.