Purpose: To analyze two gold-standard patient-reported outcome measures (PROMs) in knee OA (WOMAC and SF-36) and determine which questions are the most reflective of the overall score. Methods: This was a retrospective study on 4,983 patients with primary knee pain. Patients had WOMAC and SF-36 at two-time points, pre-treatment and after three months of treatment. A decision tree classifier supported with a linear mix model regression was applied to determine, identify, and categorize the most influential questions that determine the overall score in each of the questionnaires. Results: For SF-36, the most influential items were Q22 (39%), Q32 (24%), Q11 (19%), Q25 (19%). For WOMAC, the most influential predictors were Q14 (39%), Q10 (24%) and Q15 (21%). A significant improvement in WOMAC and SF-36 was seen after three months of treatment (P<0.01). For SF-36, the main predictor items were Q11, Q22 and Q32, Regression model R2 = 0.841, p<0.01, t[55.62]=0.001, Beta for Q22=0.409, Q32=0.352, Q11=0.278. For WOMAC, the main predictor items were Q10 and Q15, Regression model R2 = 0.930, p<0.01, t[35.4]=0.001, Beta for Q15=0.548, Q10=0.4639. Conclusion: Two questions from the WOMAC questionnaire predicts 93% of the overall score and four questions form the SF-36 predict 84%. The creation of a clinically meaningful assessment tool based on larger scientifically validated PROMs will help to facilitate its use by clinicians and acceptance by patients in clinical practice.