Ultrasound-Guided Posteromedial Fascial–Periarticular Injection for Mild-to-Moderate Knee Osteoarthritis: Twelve-Month WOMAC Outcomes in a Retrospective Pilot Case Series

Knee osteoarthritis (OA) is increasingly recognized as a whole-joint disorder involving periarticular soft tissues in addition to intra-articular structures. A recently published technical report described an ultrasound-guided posteromedial knee injection targeting a fascial–periarticular convergence region operationally termed the popliteal fascial retinaculum. In the present study, we evaluated preliminary longitudinal clinical outcomes after this procedure in patients with mild-to-moderate knee OA. Background/Objectives: Knee OA is a common cause of chronic pain, stiffness, and disability. In the present study, we evaluated preliminary 12-month WOMAC outcomes after a three-session ultrasound-guided posteromedial fascial–periarticular injection in patients with Kellgren–Lawrence grade 1–3 knee OA. Methods: This retrospective analysis of a prospectively maintained single-center clinical registry included 10 patients treated between October 2023 and October 2025. Each patient received three monthly ultrasound-guided posteromedial injections using 30 mL of 5% dextrose with 0.1% lidocaine (lignocaine). The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was recorded at baseline and at 1, 3, 6, and 12 months after the final injection. Data are mean ± SD, median (IQR), and 95% CI. In exploratory inferential analyses, we used Friedman tests and Wilcoxon signed-rank tests with Bonferroni correction. Results: The mean WOMAC total score improved from 59.5 ± 4.33 at baseline to 38.6 ± 4.50 at 1 month, 34.3 ± 4.45 at 3 months, 30.6 ± 3.06 at 6 months, and 28.5 ± 2.51 at 12 months after the final injection, corresponding to a mean 12-month within-patient change of −31.0 points (95% CI −32.58 to −29.42; −52.1%). Mean pain improved from 12.6 ± 1.35 to 5.6 ± 0.70, stiffness from 4.7 ± 0.48 to 2.1 ± 0.32, and physical function from 42.2 ± 2.62 to 20.8 ± 2.15. All 10 patients had lower WOMAC total scores at 12 months than at baseline. Friedman tests were significant for all four WOMAC domains (all p ≤ 5.05 × 10−7); Wilcoxon signed-rank tests versus baseline reached the theoretical minimum p at n = 10 (Bonferroni-adjusted p = 7.81 × 10−3) at every follow-up timepoint. No serious adverse events were documented; mild transient post-procedural soreness occurred in three patients. Conclusions: In this small retrospective pilot cohort, ultrasound-guided posteromedial fascial–periarticular injection was associated with sustained improvement in WOMAC pain, stiffness, physical function, and total scores over 12 months. These findings are preliminary and hypothesis-generating; non-specific effects including placebo, regression to the mean, and natural symptomatic fluctuation cannot be excluded. Prospective controlled trials are required to establish safety, reproducibility, mechanism, and comparative effectiveness.