Objective: To compare the effectiveness of injections of platelet-rich plasma (PRP) compared with focused extracorporeal shock-wave therapy (ESWT) among athletes with chronic patellar tendinopathy (jumper's knee).
Design: Randomized controlled single-center trial, with 12 months of follow-up.
Setting: Tertiary-level care in Rome, Italy. Patients were recruited from January 2009 to May 2011.
Participants: Patients who received a diagnosis of jumper's knee from a participating physician were recruited into the study (n = 46). Inclusion criteria were chronic (≥6 months), unilateral, proximal patellar tendinopathy in a recreational or elite athlete confirmed by ultrasound (US); prior failed nonoperative management that concluded ≥12 weeks prior to study entry; and ages 18 to 50 years. Exclusion criteria were coexisting knee lesions, systemic disorders, knee surgery or corticosteroid injection in the previous 3 months, and contraindications to PRP treatment.
Intervention: Patients in the PRP group (n = 23) received 2 US-guided injections separated by 1 week and directed at the affected tendon portion. Each injection consisted of 2 mL of nonactivated, autologous PRP extracted from a single centrifugation of 10-mL blood and administered by a trained physician via a 22-guage needle. Patients in the focused ESWT group (n = 23) received 3 treatments (2400 impulses at 0.17-0.25 mJ/mm per session) separated by 48 to 72 hours. Treatments were guided by inline US and administered by 1 experienced operator. No local anesthesia was used in either group. One week later, both groups began a conventional stretching and strengthening program for 2 weeks. At 4 weeks, patients gradually resumed normal activities and sports, as tolerated.
Main outcome measures: At 2, 6, and 12 months after treatment, patients were assessed by a single investigator, blinded to group assignment. The main measure was the Italian version of the Victorian Institute of Sports Assessment-Patella (VISA-P) questionnaire, which evaluates severity of symptoms, function, and ability to participate in sport. A 10-cm visual analog scale (VAS) was used to assess pain while doing 5 single-leg squats. Patients also assessed their response to treatment on the Blazina scale (excellent to poor). No patients were lost to follow-up
Main results: During the 12-month follow-up period, VISA-P scores for both groups improved significantly from baseline (55.3 for PRP, 56.1 for ESWT), although the PRP group had greater improvement at 6 months (86.7 vs 73.7; P = 0.014) and 12 months (91.3 vs 77.6; P = 0.026). Pain scores during 5 single-leg squats demonstrated similar findings. At 12 months a greater proportion of patients in the PRP group rated their response to treatment as good or excellent (PRP, 91.3% vs ESWT, 60.8%; P = 0.035), although at earlier follow-ups the groups did not differ. Both the injections and ESWT caused transient discomfort. No patient had surgery during follow-up.
Conclusions: Athletes with chronic patellar tendinopathy responded positively to both PRP injection and ESWT. However, the PRP-treated patients demonstrated significantly greater improvements in VISA-P and pain scores by 6 months and significantly better functional outcomes and satisfaction based on a modified Blazina scale, at 12 months.