Ultrasonographic Evaluation of Femoral Cartilage Thickness in Patients with Lumbar Radiculopathy

Background: Lumbar radiculopathy (LR) is frequently associated with proprioceptive deficits, altered load distribution, peri-knee muscle thinning, and early degenerative changes in femoral cartilage, potentially accelerating osteoarthritis development. Aim: This study aimed to assess distal femoral cartilage thickness, rectus femoris muscle (RFM) thickness and cross-sectional area, and gastrocnemius medialis muscle (GMM) thickness using ultrasonography (USG) in patients with unilateral LR. Methods: A prospective cross-sectional design was employed, including 50 patients with MRI-confirmed unilateral LR (L3–S1) of at least 3 months’ duration. Clinical assessments included the LANNS, VAS, and ODI. Bilateral femoral cartilage thickness (medial, lateral, intercondylar), RFM thickness and cross-sectional area, and GMM thickness were measured by USG. Comparisons were made between radiculopathy and intact sides and according to symptom duration (3–12 vs. >12 months). Results: The RFM cross-sectional area (4.12 ± 1.27 vs. 4.50 ± 1.18 cm², P = 0.001) and thickness (1.40 ± 0.28 vs. 1.51 ± 0.28 cm, P = 0.001) were significantly lower on the affected side. The intercondylar cartilage thickness was also reduced (0.23 ± 0.05 vs. 0.25 ± 0.05 cm, P = 0.014). Patients with symptom duration > 12 months exhibited thinner intercondylar cartilage than those with 3–12 months (0.22 ± 0.05 vs. 0.25 ± 0.05 cm, P = 0.014). Significant correlations were identified between intercondylar cartilage thickness and GMM thickness ( r = 0.316, P = 0.026) and between medial condyle cartilage thickness and RFM cross-sectional area ( r = 0.362, P = 0.010). Conclusions: LR is associated with femoral cartilage thinning and peri-knee muscle atrophy on the affected side, underscoring the risk of early osteoarthritis. Early rehabilitation strategies focusing on periarticular muscle strengthening are warranted. USG represents a practical, dynamic, and noninvasive modality for monitoring these changes.