Platelet-rich plasma (PRP) to treat chronic upper patellar tendinopathies

Background: Upper patellar tendinopathies remain often chronic and rebel to a thorough conservative treatment. Moreover, the option of a surgical treatment could be disappointing. New treatments are being developed. Injection of PRP is one of these. Platelets contain lot of growth factors which would have the potentiality to enhance the healing process of tendons. Even if in vitro and animal experiments have demonstrated this stimulation of tendon healing process1, clinical series are subject to controversy2. Methods: Twenty patients with chronic upper patellar tendinopathy were enrolled. Assessments ［VAS, clinical examination with an algometer, algofunctional scores (IKDC and VISA-P), functional assessments (isokinetic and Optojump) and imagery (ultrasounds and MRI)］were made before infiltration of PRP, and 6 weeks and 3 months after. The PRP was obtained by an apheresis system (COM.TEC, Fresenius). Six millilitres of PRP were injected without local anaesthetic. One week after infiltration, patients started a 6-week standardised sub-maximal eccentric reeducation. Results: We observed a very significant improvement of the algofunctional status as soon as 6 weeks after the infiltration of PRP, and continued to a lesser extent up to 3 months. During functional evaluation, pain decreased as well, but without significant improvement of performances. No significant improvements in the imagery were observed. Interestingly, patients who had a VAS equal or below 1 after 3 months post-infiltration were younger (24.7 vs 32.2 y.o.). Moreover, these younger patients had a significant increase of the IKDC score (p=0.003), a significant improvement of pain during isokinetic evaluations (p