Table 1.
Patient-reported measures and their psychometric properties for knee OA.
| Outcome | Observations | Scoring | Psychometrics |
|---|---|---|---|
| Visual Analogue Scale (VAS) | The purpose of VAS is to measure pain. The scale is placed in front of the patient who is asked to rate their pain intensity according to a pre-determined period of time. VAS can be used before, during, or after physical function tests. | From 0 to 10 cm (0 – the complete absence of pain, and 10 – maximum intensity). | A pain reduction of 1.75 cm on the scale is the recommended MCID in OA research.103 |
| Numeric Rating Scale (NRS) | The purpose of NRS is to represent a unidimensional measure of pain. Usually, it is a segmented numeric version of VAS, and it can be administered verbally (also by telephone) or graphically for self-completion. The scale is placed in front of the patient who is asked to rate their pain intensity according to a pre-determined period of time. NRS can be used before, during, or after physical function tests. | A 0–10-point numeric scale with 0 representing “no pain” and 10 representing “pain as bad as you can imagine”/“worst pain imaginable.” | A pain reduction of 2 points on the scale is the recommended MCID in patients with chronic musculoskeletal pain.104 |
| Western Ontario & McMaster Universities Osteoarthritis Questionnaire (WOMAC) | WOMAC is a self-report questionnaire designed to assess the problems experienced by individuals with lower limb OA in the past 72 h. It contains 24 specific questions divided into three domains: pain, stiffness, and physical function. | The score of each question ranges from 0 to 4. The total questionnaire score is 96, with high scores representing worse results. | An improvement greater than or equal to 12% from baseline is the recommended MCID in OA research.105 |
| Knee Injury and Osteoarthritis Outcome Score (KOOS) | This self-report questionnaire assesses the problems experienced by people with lower limb OA in the prior week by measuring quality of life and knee function. It contains 42 questions in 5 domains: pain, other symptoms, function in daily life, sports-related function and recreation, and knee-related quality of life. | The answers are standardized and scored from 0 to 4. The total score of the questionnaire is 168. High scores indicate worse results than low scores | A difference of 8–10 in the total score from baseline is the recommended MCID in OA research.106 |
| Algofunctional indices for the knee or index of severity for knee disease (Lequesne Index) | This index is used specifically for the evaluation of pain, maximum walking distance, and daily activities of patients with OA. | The 10-item questionnaire is scored on a 0–24-point scale. Lower scores indicate there is less functional impairment, and higher scores reflect the worst outcomes. The sum of the scores is classified as: little effect (1–4 points), moderate effect (5–7 points), severe effect (8–10 points), very severe effect (11–13 points) and extremely severe effect (greater than or equal to 14 points). | The MCID for the Lesquene Index is still not established in knee OA research. |
| Short Form-36 questionnaire (SF-36) | The short form questionnaire is intended to measure the patient's quality of life with 36 items referring to the past four weeks. It presents a multiple-choice scale that evaluates eight domains of life: Physical Functioning, Role Limitations due to Physical Problems, General Health Perceptions, Vitality, Social Functioning, Role Limitations due to Emotional Problems, General Mental Health and Health Transition. | The sum of the total value varies from 0 to 100, with higher indexes indicating a better quality of life. Each of the eight summed scores can be linearly transformed into a scale from 0 (negative health) to 100 (positive health) to provide a score for each subscale. Each subscale can be used independently. | A difference of 10 points is recommended as an MCID in OA research.107 |
| Short Form-12 questionnaire (SF-12) | The short form questionnaire is intended to measure the patient's general physical and mental well-being, which is based upon the SF-36 score. It has two components, the physical component summary (PCS) and the mental component summary (MCS) scores. | Scores are reported on a scale of 1–100 with a higher score representing a better health status. The score is calculated independently for each component according to the responses recorded on Likert scales of six questions (each). Scores are converted into the validated score using a defined algorithm. | An improvement of 4.5 points for the physical component and 4.8 points for pain relief and function are established as MCID in OA research for patients after knee arthroplasty.108 |
| Health Assessment Questionnaire (HAQ) | A self-administered questionnaire consisting of 20 detailed questions of people's daily activities divided into eight categories: dressing and activities related to taking care of appearance, getting up, eating, walking, hygiene, reaching, gripping, and daily life activities. | Each patient assesses the difficulty they face carrying out each activity on a scale from 0 to 3, where zero means no difficulty performing and three means unable to perform the activity. Increasing scores indicate worse functioning with 0 indicating no functional impairment and 3 indicating complete impairment. | The MCID for the HAQ questionnaire is still not established in knee OA research. |
MCID, minimal clinically important difference; OA, osteoarthritis.