Psychosocial Predictors of Poor Outcomes After a Knee Arthroplasty

Participants will be asked to rate their pain at resting, walking and flexing their knee on a horizontal 100-mm Visual Analogue Scale (VAS). The horizontal line anchors will be "no pain" and "worst imaginable pain". The VAS is a valid and reliable instrument compared with other pain rating scales, and has been well established in clinical practice and research for measuring pain levels in arthritis populations.

Western Ontario and McMaster University Osteoarthritis Index (WOMAC) (Spanish version) will be used to assess patient´s physical function. This questionnaire can be completed in less than 5 minutes. It's a widely used, reliable, valid and responsive measure of outcome in people with osteoarthritis of the hip or knee.

The spanish version of the Euro Quality of Life 5D-5L (EQ-5D-5L) was used to assess the health related quality of life (HRQL).(10) The EQ-5D-5L consists in two pages: the first one is based on a descriptive system that defines health in terms of five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Each dimension has five response categories: no problems, slight problems, moderate problems, severe problems, extreme problems.(10) A health state is composed by taking one level for each dimension, and a preference-based scoring function is used to convert the descriptive system to a summary index score (ranging from states worse than dead <0 to full health 1).

Participants will be asked to complete the Tampa Scale for Kinesiophobia (TSK-11) (Spanish version). TSK-11 is a 11 item self-administered questionnaire used to assess the pain-related fear of movement. The TSK-11 uses a 4-point Likert scale with responses ranging from 1 = totally disagree, to 4 = totally agree. Overall scores range from 11 to 44 indicating a higher degree of pain-related fear of movement when the score is higher.

Participants will be asked to complete the Spanish version of Survey of Pain Attitudes - Brief (SOPA-B). The SOPA-B is a 30 item self-administered questionnaire which evaluates the pain attitudes and is composed of 7 subscales: solicitude, emotion, medical cure, control, physical harm, disability and medication. This questionnaire uses a 5-point Likert scale with responses ranging from 0 = very false to 4 = very true.

Participants will be asked to complete the Hospital Anxiety and Depression Scale (HADS) (Spanish version) will be used. The HADS is a 14 item self-administered questionnaire comprised of 2 subscales: depression and anxiety, both composed with 7 items. Each item use a 4-point Likert scale with responses ranging from 0 to 4. Overall scores range from 0 to 21 points for each subscales, and final score is presented using each subscale scores separately. The higher the score, the higher are the anxiety or depression levels.

Goniometric assessments of knee will be carried out to assess flexion and extension range of motion.

The Spanish version of Pain Catastrophizing Scale (PCS) was used to asses thoughts and feelings related to pain experiences.(9) The PCS is a 13 item self-administered questionnaire composed of 3 subscales: rumination, magnification and helplessness. The PCS uses a 5-point Likert scale with responses ranging from 0 = not at all to 4 = all the time. Overall scores range from 0 to 52 points, the higher the score, the higher is the pain catastrophism level.

30-Second Chair Stand Test (30sCST) will be use to evaluate patient's functionality on standing, because it is a well-recognized test to detect early declines in functional independence.

4 Meters Walking Test (4MWT) will be used to evaluate patient's walking speed.