Diagnostic Accuracy of Quadriceps Muscle Strength Measure in Discriminating between Knee Osteoarthritis Patients with Mild and Moderate to Severe Radiographic Signs

Accurate diagnosis and discrimination of quadriceps muscle weakness between mild and moderate to severe grades of knee osteoarthritis (OA) can help timely treatment and prevention of future complications. Thus, our aim of this study was to evaluate the accuracy of quadriceps strength measure and to determine its optimal cutoff point in discriminating between two groups of mild and moderate to severe knee OA radiographic sign.
Subjects and Based on the Kellgren-Lawrence (KL) grading scale, a total of 130 knee OA patients were classified into 65 patients with mild (a KL grade≤ 2) and 65 patients with moderate to severe (a KL grade≥3) radiographic sign. Quadriceps muscle strength was assessed using isometric dynamometer. The accuracy of this measure was determined by calculation of sensitivity, specificity, area under the Receiver Operating Characteristic (ROC) curve (AUC), likelihood ratios (LR), and predictive values (PV). Our results showed that quadriceps muscle strength had high sensitivity and good level of accuracy in discriminating between the two groups of knee OA patients. Also, based on LR and PV results, quadriceps muscle strength had good ability for ruling out moderate to severe grade of knee OA patients and accurate diagnose of mild grade of patients, respectively. Our findings provide evidence for good accuracy of quadriceps muscle strength in discriminating between the two groups of knee OA patients. Thus, it may be recommended that this measure be evaluated before planning for intervention