Primary knee osteoarthritis: do the clinical and functional outcomes of intra-articular PRP correlate with MRI structural changes?

Abstract Background Knee osteoarthritis (KOA) is a common degenerative joint disorder causing pain, functional limitation, and reduced quality of life. In recent years, intra-articular platelet-rich plasma (PRP) has emerged as a promising biological therapy; however, its structural effects on joint tissues remain unclear. Objective This study aimed to evaluate the clinical, functional, and structural effects of intra-articular PRP injections in patients with primary KOA, and to determine whether the improvements in symptoms are associated with significant changes in the MRI findings. Methods Forty patients with primary KOA underwent two consecutive intra-articular PRP injections. At baseline and the 6-month follow-up, patients were evaluated clinically and functionally using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), as well as by MRI using the MRI Osteoarthritis Knee Score (MOAKS). Baseline MRI was scored for cartilage defects, bone marrow lesions (BMLs)/cysts, effusion, osteophytes, meniscal lesions, cruciate ligament lesions, intra-articular loose bodies, peri-articular bursitis, and patellar tendinitis. At follow-up MRI, the total disease course and individual courses of cartilage defects, BMLs, and effusion were evaluated. Pearson’s chi-squared, Student’s t, and Cohen’s kappa tests were performed. Results All WOMAC parameters and joint tenderness showed significant improvement at follow-up ( P < 0.05). Despite the significant variation of BMLs among its different grades ( P < 0.05), the improvement was not significant, with no significant differences between baseline and follow-up MRI grading of cartilage defects, BMLs, and effusion ( P = 0.93, 0.31, and 0.21, respectively). WOMAC parameters were significantly lower in the absence of cartilage lesions and BMLs at follow-up MRI ( P < 0.05). The inter-observer agreement was moderate regarding baseline and follow-up grading of cartilage defects and effusion, while it was poor to fair in BMLs grading. Conclusions The positive clinical and functional outcomes of PRP in primary KOA were not associated with significant improvement in the structural MRI findings. Patient satisfaction after PRP therapy was significantly better in the absence of MRI abnormalities.