Efficacy and safety of treating symptomatic, primary focal osteochondral lesions of the patella with a combination of intra-articular injection of hyaluronic acid (HAi) and radial extracorporeal shock wave therapy (rESWT) or HAi alone: A retrospective two-cohort study

Abstract Background: This study tested the hypothesis that a combination of intra-articular injection of hyaluronic acid (HAi) and radial extracorporeal shock wave therapy (rESWT) is more effective than HAi alone in the treatment of symptomatic, primary focal osteochondral lesions of the patella (sPFOLP).Methods: We performed a retrospective analysis of n=81 subjects with unilateral sPFOLP who were treated with respectively HAi+rESWT (n=36) or HAi alone (n=45) at the outpatient department of our hospital between January 1st, 2014 and January 31th, 2018. Subjects in both cohorts also received education with special attention to reduction of going up and down the stairs, squatting and specific activities, as well as non-opioid analgesics if necessary. Efficacy was assessed using the pain visual analogue scale (VAS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, which were examined at baseline (BL) and six weeks (W6), three months (M3) and six months (M6) after BL, as well as during a last follow-up examination (LE) which was performed at 37.6 ± 1.7 (mean ± standard error of the mean) months after BL (range, 12-59 months). In addition, measurements of the area of the patellar bone marrow edema (PBME) on sagittal, fat suppression sequence magnetic resonance imaging (MRI) scans of the knee were performed at BL, M3, M6 and LE. Results: Subjects who were treated with HAi+rESWT showed significantly smaller mean VAS pain scores at W6, M3 and M6, significantly smaller mean WOMAC scores at W6, M3 and LE and significantly smaller mean PBME areas at M3, M6 and LE than subjects who were treated with HAi alone. No severe adverse events were observed.Conclusion: The results of this study suggest that HAi+rESWT is safe and more effective than HAi alone in the treatment of sPFOLP. This result should be verified in adequate randomized controlled trials. Level of Evidence: Level III; retrospective two-cohort study.