The use of PRP has been shown to add stem cells to the tissue, which stimulated the production of new tissue and directly influences ligament healing.
Murray et al. (2003) investigated the action of growth factors during treatment of anterior cruciate ligament (ACL) injuries in the knee. MRI demonstrated the evolution of ACL ligament healing, and was followed up with biomechanical tests to determine traction properties. Ovine studies (Murray et al. 2009) have also presented promising results regarding the use of PRP in the treatment of ACL. Several recent studies have attracted attention for finding positive effects with PRP in ligament injuries, such as Sánchez et al. (2003b), who in a retrospective clinical trial reported fewer complications and better healing after applying PRP to 100 patients submitted to ACL reconstruction. A prospective single-blind study by Radice et al. (2010) evaluated, using MRI images of the interior of the ACL graft, 50 patients who had undergone ACL reconstruction for the first year after the procedure.
In a recent further clinical trial, randomized and controlled, de Almeida et al. (2012) selected 27 patients that were divided at random to receive (n - 12) or not to receive (n - 15) PRP injections on the patellar tendon collection site at the knee during surgery for reconstruction. The results were assessed by MRI after 6 months. The researchers observed that the recuperation of the opening site of the patellar tendon was significantly bigger in the PRP group than in the control group. The visual analogue scale (VAS) was also used and the post-surgery pain score was significantly lower in the group treated with PRP. Concluding, that PRP improves the healing of the tissues on the collection site of tendons and ligaments and this was confirmed. PRP also reduced the pain after surgery.