Association of Baseline Femoral Trochlear T2*Mapping with Clinical Response to Platelet-Rich Plasma in Patellofemoral Chondropathy: A Retrospective Exploratory Study

Abstract

Background: Platelet-rich plasma (PRP) is utilised in the treatment of patellofemoral chondropathy, although clinical responses remain variable. This retrospective exploratory study assessed whether baseline quantitative T2 mapping of femoral cartilage was associated with clinical improvement following PRP administration. Methods: In this retrospective observational study conducted within routine clinical practice, patients with patellofemoral chondropathy received three ultrasound-guided intra-articular PRP injections administered weekly according to an institutional protocol. Baseline and 9-month T2-mapping MRI scans and clinical questionnaires were collected as part of standard follow-up. The main imaging variable was the worst-region femoral trochlear T2 value, evaluated as a candidate prognostic biomarker. Clinical outcomes included the Visual Analogue Scale (VAS, 0-10) and Kujala (0-100) scores, with responders defined by minimum clinically important difference (MCID) thresholds (?VAS ? 1.5; ?Kujala ? 8). Results: Thirty-two knees from 22 patients completed follow-up, including 10 bilateral cases (19 right knees, 13 left knees). Both VAS and Kujala scores improved significantly at 9 months (p < 0.001 for both). Baseline femoral trochlear worst-region T2 values were inversely correlated with pain and functional improvement (?VAS: rho = -0.51, p = 0.003; ?Kujala: rho = -0.36, p = 0.042). Baseline patellar T2 values were not associated with clinical change (?VAS: rho = -0.18, p = 0.32; ?Kujala: rho = -0.12, p = 0.51). Sensitivity analyses using baseline mean femoral T2 values did not show significant associations with ?VAS or ?Kujala. Interobserver reproducibility for the worst-region T2 metric was limited, particularly for the femoral compartment (femur ICC 0.37; patella ICC 0.47), which limits immediate clinical applicability. Mean regional longitudinal ?T2 changes did not exceed the 14% QIBA MDC95 threshold. Conclusions: In this small retrospective cohort, baseline femoral trochlear worst-region T2 values were associated with clinical improvement after PRP. These preliminary hypothesis-generating findings should be interpreted with caution and require validation in larger controlled cohorts with standardised and reproducible segmentation workflows.