Accuracy of Ultrasonography in Comparison with Magnetic Resonance Imaging to Detect Meniscal Tears in Knee Injuries

Abstract

Meniscal tears are common in active adults, and timely imaging guides triage to conservative care or arthroscopy. While MRI is the reference standard, ultrasonography (US) offers a low-cost, accessible alternative. Objective: To determine the diagnostic accuracy of high-resolution US for detecting meniscal tears using MRI as the reference standard. Methods: We conducted a cross-sectional diagnostic-accuracy study of 304 participants (mean age 29.9 ± 7.57 years; 61% male). At radiology department of JPMC karachi from 1st August 2024 till 31st January 2025.All underwent standardized knee US followed by MRI. Meniscal tear status on US was compared with MRI using 2×2 tables to compute sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy. Discrimination was assessed with receiver operating characteristic (ROC) analysis. Results: US identified tears in 207/304 (68.1%), while MRI showed tears in 222/304 (73.0%). Cross-tabulation yielded 193 true positives, 14 false positives, 68 true negatives, and 29 false negatives. Using MRI as reference, US achieved sensitivity 86.9%, specificity 82.9%, PPV 93.2%, NPV 70.1%, and accuracy 85.9%. ROC analysis demonstrated AUC 0.847 with p < 0.0001, indicating good overall discrimination. Conclusion: High-resolution ultrasonography showed good diagnostic performance versus MRI, with particularly strong rule-in value given its high PPV. In resource-constrained or high-throughput settings, US can function as an effective first-line triage tool, reserving MRI for equivocal cases or when clinical suspicion persists after a negative US.