Regarding psychosocial factors and outcomes in total knee arthroplasty (TKA), most of the current literature and the investigators' previous work suggest that depression, anxiety and pre-operative pain strongly predict worse outcomes following TKA. Despite some conflicting evidence, on the whole, the current literature suggests that psychological intervention in TKA patients could help to improve outcomes. In recent years, Acceptance and Commitment Therapy (ACT) has been receiving more attention as it may be more effective than the more traditional cognitive behavioural therapy in treating older people with chronic pain. ACT includes a combination of acceptance and mindfulness methods along with activation and behaviour change methods.

There have been several studies examining ACT in patients undergoing orthopaedic surgery. These studies have found that attending a pre-operative ACT workshop and receiving text messages reinforcing ACT can reduce use of pain medication, reduce post-operative pain and improve function following surgery. There are also two study protocols published which plan to investigate ACT in TKA patients but the findings of these studies are yet to be reported.

In this feasibility study, the investigators propose to investigate the acceptability and feasibility of a pre-operative ACT workshop in TKA patients considered to be at risk of poorer outcome based on a depression score. If found to be acceptable and feasible to both patients and those who will deliver the ACT sessions, a larger study will be performed.

Regarding psychosocial factors and outcomes in total knee arthroplasty (TKA), most of the current literature suggests that depression, anxiety and pre-operative pain strongly predict worse outcomes following TKA. The investigators' previous work agreed with these findings and other psychological factors, such as neuroticism, pain catastrophising and self-blame were associated with worse outcomes up to 1 year following TKA whilst conscientiousness, pain self-efficacy and extraversion were associated with better outcomes up to 1 year following TKA. These psychological factors have been less consistently associated with outcomes following joint arthroplasty in other papers and several papers have found no evidence or conflicting evidence that depression or anxiety are associated with outcomes following TKA. Despite some conflicting evidence, on the whole, the current literature suggests that psychological intervention in TKA patients could help to improve outcomes.

To date, few studies have randomised patients to a psychological intervention or control group to determine whether intervention could improve outcomes following TKA or total hip arthroplasty (THA). A systematic review by Bay et al. (2018) reported that the current literature, which is still in its infancy, does not support routine psychological interventions for TKA or THA. This review included seven studies of randomised controlled trials (RCTs) of psychological interventions which involved active patient participation measured with patient reported outcomes in THA or TKA patients. Only two of these studies found psychological interventions to be effective in improving at least one patient reported outcome. One study used a combination of cognitive behaviour therapy and relaxation therapy in THA patients and this was found to significantly improve hip function at 1-year follow-up. In the second study, guided imagery improved gait velocity 6 months after TKA, and reduced knee pain 3 weeks after surgery compared to the control group.

Recently, ACT has been receiving more attention as it may be more effective than the more traditional cognitive behavioural therapy in treating older people with chronic pain. ACT includes a combination of acceptance and mindfulness methods along with activation and behaviour change methods. The goal of ACT is to enhance psychological and behavioural flexibility by cultivating the six inter-rated skills of acceptance, cognitive defusion, present-moment awareness, values clarification, committed action, and perspective taking.

In the current literature, there have been several studies examining ACT in patients undergoing orthopaedic surgery. One study included 88 veterans who were undergoing orthopaedic surgery (including TKA, THA, shoulder and spine). Half of the patients were randomised to standard care and the other half attended a 1-day ACT workshop pre-operatively in addition to standard care. Pain levels and opioid use were assessed up to 3 months following surgery. The intervention group achieved pain and opioid cessation sooner than those in the control group. Increases in pain acceptance and values-based behaviour, processes targeted in ACT, were related to better outcomes. The other study included 76 patients who underwent operative fixation of a traumatic upper or lower extremity fracture. Patients were randomised to the intervention group, who received twice-daily text messages communicating an ACT-based intervention for the first 2 weeks after surgery, or the control group, who received no text messages. At baseline, patients completed paper forms comprising a basic demographics questionnaire and baseline patient-reported outcomes. Two weeks following surgery, patients again completed the patient reported outcomes and had an opioid medication pill count. On average, the intervention group used 36.5% fewer opioid tablets compared to the control group (intervention group average: 26.1 (SD 21.4) tablets, control group average: 41.1 (SD 22.0) tablets). The intervention group also reported significantly lower post-operative pain compared to the control group. The same group of authors then investigated ACT using the same intervention (text messages sent twice a day for 2 weeks) to a total of 45 THA and TKA patients who had their surgeries delayed due to the Covid-19 pandemic. They found that the ACT group showed improved function and slowed decline compared to the other 45 in the control group who did not receive any text messages.

There are also two study protocols published which plan to investigate ACT in TKA patients but the findings of these studies are yet to be reported.

Based on the investigators' previous work, psychological factors are associated with TKA outcomes, therefore, in this feasibility study, the investigators propose to examine the acceptability and feasibility of a pre-operative ACT workshop in TKA patients considered to be at risk of poorer outcomes based on a depression score. If found to be acceptable and feasible to both patients and those who will deliver the ACT sessions, a larger study will be performed to determine whether ACT can improve outcomes in TKA patients.

The aim of this feasibility study is to determine the acceptability and feasibility of a half day pre-operative ACT workshop, ACT text messages and follow-up with a physiotherapist in a cohort of patients undergoing TKA who have been identified as having a higher likelihood of a below average post-operative outcome.

Inclusion Criteria:

• Patients ≥ 18 years old scheduled for routine primary elective TKA.
• Participants must have a functional level of spoken and written English and be able to complete the online pre-operative psychosocial questionnaire independently.
• Patients must have scored 10 or more on the Depression subscale of the (Depression, Anxiety and Stress Scale) DASS-21 of the pre-operative psychosocial questionnaire.

Exclusion Criteria:

• Any patient who does not have access to a mobile phone to receive the booster text messages, or online facilities to answer online questionnaires.
• Any patient who has a significant change (≥3 months) in scheduled date of surgery i.e. has a delayed surgery or surgery earlier than expected.
• Any patient who does not attend the pre-operative education class.
• Any patient scheduled for revision, uni-compartmental or bilateral TKA.
• Any patient who has further orthopaedic surgery planned in the next 3 months.
• Any patient who cannot commit to the schedule of events.
• Any patient currently receiving any other "talking therapy".

The Chief Investigator will be blinded to what group patients are randomised to. It will not be possible to blind the patients, research team or physiotherapists involved in the study.