The Association Between Pre-operative Pain Psychology and Hypersensitivity With Poor Functional Outcome After Knee Replacement.

To explore whether there are factors that help us to understand why some patient outcomes are not successful and identify prediction factors for progression. Assess central pain sensitisation and psychology pre- and post-surgery with reliable tools that explore prediction tools for good/poor progression and improve patient selection, patient preparation and timing for surgery.

The aim of this project is to explore the effects of pre-surgical central pain sensitisation on pain and function outcomes post-TKA. Central pain sensitisation will be assessed using pressure algometry and the Pain Catastrophizing Scale will be used to explore pain psychology. Functional outcomes post-TKA will be assessed using a commonly used scale for patients' self-reported outcomes (Oxford Knee Score), visual analogue scale, a star excursion balance test and four recommended patient performance-based tests.

Knee osteoarthritis (OA) is a major cause of disability around the world; it is the most common chronic condition in primary care in the UK. By 2030 it is predicted to be the greatest cause of disability in the general population. An effective end-stage treatment for knee OA is knee-replacement surgery, which was first done in the 1970s and 1980s.

In England and Wales, the number of knee-replacement procedures recorded by the National Joint Registry in 2013 was 91,703, which represents an increase of 0.9 % over 2012. The data analysis by the National Joint Registry and the Office of National Statistics suggests that, by 2030, primary TKAs will increase by 117% from the 2012 level. Subsequently, TKA revision surgeries are expected to increase incrementally by 332%. There is a similar estimation of demand for revision TKA surgeries in the United States; by 2030, they are expected to rise by 601% from the 2005 level. The United States estimation of primary TKA is for growth of 673% from the 2005 level, which is similar to England and Wales's upper-limit projections.

Post-TKA, 75-85% of patients report satisfaction with surgery outcomes, while the remaining 15-25% are dissatisfied . Total knee arthroplasty's success has traditionally been evaluated from the surgeon's perspective, e.g. the presence of surgical complications or implant survival. This is gradually changing to involve the patient in measuring health outcomes and decision-making processes. Patient-reported outcome measures (PROMs) have evolved to explore patient perspectives by monitoring the quality of care in health organizations and conducting clinical trial outcomes.

Worldwide National Joint Registry summarise the common indication for TKA revision are; 29.8% due to aseptic loosening, 14.8% infection and 9.5% due to pain. Most prediction studies show that pain and psychology pre-operation may predict poor outcomes post-TKA. A systematic review by concludes that pain catastrophizing predicts chronic pain post-TKA. Pain catastrophizing is defined as a construct that reflects anxious preoccupation with pain, an inability to inhibit pain-related fears, amplification of the significance of pain vis-à-vis health implications, and a sense of helplessness regarding pain.

Chronic post-surgery pain is significantly associated with preoperational central sensitisation as in post-shoulder subacrominal decompression and hernia repair. Regarding post-TKA, a study by Lundblad et al. (2008) concluded that the preoperational hand electrical pain threshold significantly predicts pain outcomes one year post-TKA. The study explored the association between chronic pain post-TKA and preoperation widespread pain sensitisation using pressure algometry. Both study association without control the psychological confiding factor. The correlation with Western Ontario and McMaster Universities Osteoarthritis Index pain score (WOMAC) is questionable due to weakness of WOMAC with post TKA population such as low sensitivity of WOMAC's stiffness subscale reduces the overall standardized response mean and high ceiling effect Psychological pain thinking is assessed using the most widely used measuring scale: Pain Catastrophizing Scale (PCS). PCS assesses pain thinking in three dimensions: rumination ("I can't stop thinking about how much it hurts"), magnification ("I worry that something serious may happen") and helplessness ("It's awful and I feel that it overwhelms me").

The current study will investigate preoperational central sensitisation using pressure algometry, in addition to the Pain Catastrophizing Scale (PCS), to explore psychological factors. There may be some correlation between preoperational central sensitisation and post-TKA outcomes such as pain and functional improvements.

To the best of our knowledge, no previous study has explored central sensitisation using pressure algometry and the Pain Catastrophizing Scale and possible correlation with its effects on pain and function recovery post-TKA. Pain and function can be accurately assessed before and after TKA using visual analogue scale, Oxford Knee Score, balance and performance functional tests. No previous study has correlated preoperational central sensitisation and pain psychology post-TKA on the Oxford Knee Scale as commonly used patients' self-reported outcome measures.

Thus, the study may explore accurate and objective prediction factors of post-total-knee arthroplasty progression. Potentially, reliable outcome prediction could, however, improve patient selection for surgery, as appropriate timing for surgery depends on patient symptoms and efficient patient preparation for surgery if it is to be cost-effective. Accurate preoperative prediction is crucial to minimize the potential for unrealistic expectations.

Eligibility Criteria:
Inclusion Criteria:

* All patients scheduled for elective primary unilateral total knee arthroplasty for end-stage knee osteoarthritis with stable and controlled medical condition

Exclusion Criteria:

Potential research participants were excluded from the study if ;

* The patients schedule for bilateral knee arthroplasty or unilateral knee revision surgery.
* The patient cannot read and understand English language.
* Their function limited due to other musculoskeletal involvements other than unilateral knee osteoarthritis.
* Diagnosed with uncontrolled diabetes mellitus or blood pressure.
* Diagnosed with any neurologic disorders such as stroke, Parkinson disease or multiple sclerosis.
* morbid obese patients their body mass index BMI greater than 40.
* Advance osteoporosis or other unstable chronic disease.
* Diagnosed with peripheral vascular diseases or uncontrolled cardiac diseases.
* The participant will excluded post-surgery if they develop any surgical complication such as deep vein thrombosis, uncontrolled infection, or fracture