Abstract
BACKGROUND: Chronic knee pain is highly prevalent among older adults and contributes substantially to mobility limitation and reduced quality of life. Emerging evidence suggests that periarticular muscle degeneration, particularly fatty infiltration and atrophy, plays an important role in symptom severity and functional decline. Magnetic resonance imaging (MRI) allows direct visualization of muscle quality, and semi-quantitative visual grading may offer a practical approach suitable for routine clinical practice. OBJECTIVE: To evaluate thigh and peri-knee muscle quality using a semi-quantitative MRI visual grading system in elderly patients with chronic knee pain and to examine its association with pain severity and functional limitation. METHODS: This cross-sectional study included 150 elderly patients who underwent routine MRI of the knee and the corresponding thigh. Fatty infiltration and muscle bulk were graded visually on a 0-3 scale for major muscle groups, including the quadriceps and hamstrings. Subcutaneous fat prominence was similarly assessed. Pain severity and functional limitation scores were recorded. Pearson correlations were used to assess associations between MRI scores and clinical measures. RESULTS: The mean age was 65.6 ± 6.3 years, and 54.7% were women. Quadriceps muscles demonstrated the greatest degree of fatty infiltration (mean score 1.7 ± 0.8), with 58% showing moderate to severe changes. Quadriceps bulk loss was observed in 55% of participants. Visual muscle scores showed significant correlations with pain severity and functional limitation, with the strongest associations observed for quadriceps fatty infiltration (r = 0.46-0.51) and quadriceps bulk loss (r = 0.49-0.53). Subcutaneous fat prominence demonstrated weaker but statistically significant correlations. CONCLUSION: Semi-quantitative visual MRI assessment reveals substantial muscle degeneration among elderly patients with chronic knee pain, particularly involving the quadriceps. These visual findings correlate strongly with clinical severity and demonstrate high reproducibility, supporting their utility in routine MRI interpretation. Incorporating systematic muscle evaluation into standard knee MRI may help identify patients at risk for functional decline and inform targeted rehabilitation strategies.