The purpose of this study is to test whether adding a treatment using pain neuroscience education (PNE) and multimodal physiotherapy to usual care, in subjects with knee osteoarthritis and pain catastrophizing, who are scheduled for a total knee arthroplasty (TKA), is more effective than only usual care. There is a high evidence level of different systematic reviews, which support the efficacy of physiotherapy treatments combined with behavioural/educational techniques aimed to reduce pain catastrophism, pain and disability in other pathologies. The primary aim of that kind of interventions is to help the subjects to reconceptualise its own pain understanding and its role on the recovery process, as well as promoting an increase of activity and encourage the subject to resume its usual activity instead of continuing to avoid it.

The prevalence of TKA has increased dramatically during the last two decades, its popularity can be attributed to its evident success regarding pain improvement, deformity correction and disability reduction in knee osteoarthritis subjects. However, only a third of the patients report no functional problems after surgery, the 20% of then are unsatisfied with its functional skills and around a 20% are experiencing pain, high disability degrees and a significant quality of life reduction. This results cannot be fully explained by mechanical processes, surgical procedures or surgery variations, but it seems to be related to other psychological aspects. Chronic pain subjects often develop maladaptive thoughts and behaviours (i.e. pain catastrophism, Kinesiophobia, activity avoidance) which contribute to make the subject suffer physically as well as emotionally, and affect on the intensity and persistency of pain.

Although many psychosocial factors have been studied, pain catastrophism has emerged as one of the most important predictors for persistent pain after a total knee arthroplasty, as well as its severity and duration, that's why it is getting more importance when it comes to study chronic pain in this subjects. Reducing pain catastrophism has become a key factor to determine the success in the rehabilitation of some maladies accompanied by pain, considering that its reduction has been associated with the clinical improvement of pain itself. It has been observed that treatments using psychological and psychosocial interventions, therapeutic education and coping skills training, or physical therapy and therapeutic exercise, are effective techniques to reduce pain catastrophism. Nevertheless, it's still necessary to determine whether the maladaptive pain related thoughts approach, using physical therapy and behavioural techniques, are able to reduce the risk of suffering postoperative chronic pain.

Inclusion Criteria:

• To have sufficient Spanish or Catalan reading, writing and speaking skills to comprehend all explanations and to complete the assessment tools.
• Be able to provide the informed consent.
• Be scheduled to undergo in a total knee arthroplasty.
• Primary knee osteoarthritis diagnosis.
• Score more than 20 points in the Pain Catastrophizing Scale (PCS).
• Score more than 4 over 10 on pain Visual Analogue Scale (VAS)
• Patients older than 18 years old.

Exclusion Criteria:

• Patients scheduled to undergo in a total knee arthroplasty because of prostheses replacement, tumor, infection or fracture.
• Patients scheduled to undergo in a bilateral total knee arthroplasty.
• Patients that will need another total knee or hip replacement surgery in less than a year regarding the current intervention.
• Patients scheduled for unicompartmental knee arthroplasty.
• Patients with other pathologies with characteristic features of a central sensitization. (i.e. Fibromyalgia)
• Co-existing other inflammatory or rheumatic conditions (i.e. rheumatoid arthritis, psoriatic arthritis, systemic lupus erythematosus or ankylosing spondylitis)
• Co-existing other mental condition and/or major depression.

Single blind