Fulfilment of the patient’s expectations is one of the chief determinants of satisfaction after TKA. Noble et al. studied the factors contributing to satisfaction after TKA and their relative importance. A total of 253 patients with unilateral TKA at 1 year after surgery completed a self-administered validated Knee Function Questionnaire. The questionnaire assessed patients’ range of activities involving the knee, their level of satisfaction and fulfilment of expectations from the surgery. Seventy-five percent of the patients were either satisfied or very satisfied whilst 14 % were either dissatisfied or very dissatisfied and the remainder neutral. Satisfaction with TKA correlated with age less than 60 years, absence of residual symptoms, fulfilment of expectations and absence of functional impairment. They suggested that satisfaction with TKA was primarily determined by patient expectations and not by the absolute level of function [3].

In a cross-sectional study by Bourne et al. on 1,703 primary TKA patients, 19 % were not satisfied with the surgery. The authors found that the strongest predictors for dissatisfaction were expectations not met, a low 1-year Western Ontario McMaster University Osteoarthritis Index (WOMAC), preoperative pain at rest and a post-operative complication requiring repeat hospital admission [5]. This study also reemphasised the importance of meeting patient expectations for a satisfactory outcome from TKA.

Scott [6] categorised patients into those with realistically high expectations and those with unrealistically high expectations. Patients who are younger, more physically active, with lower body mass index (BMI), higher baseline function and lower baseline pain levels may be categorised as those with realistically high expectations and tend towards a higher level of fulfilment of expectations. On the contrary, older patients with poor baseline activity levels and worse baseline pain who expect total pain relief and complete recovery of function fall into the category of unrealistic high-expectations group. This category of patients has lower levels of satisfaction after surgery.

What patients expect from surgery can be highly variable in terms of extent of pain relief and limitations in daily and recreational activities and not always expressed during consultation before surgery. It is therefore germane for the surgeon to explore patient expectations and to assess if they are realistic. Patients with unrealistic expectations should be counselled about the mismatch between what they expect and what the surgery can likely offer them.

The primary aim of TKA is relief of pain. Persistent pain after surgery is considered unacceptable by patients and can be a source of dissatisfaction. Persistent pain may have a demonstrable cause including infection, loosening, malalignment, incorrect sizing, patellar maltracking, instability, arthrofibrosis and soft tissue impingement. Most of these problems can be prevented by meticulous surgical techniques which help achieve superior results and reduce the incidence of preventable complications and dissatisfaction [6].

However, there is a subset of patients who have persistent pain in a well-done TKA for which there is no obvious cause. That is, the knee is well aligned and stable with a functional range of motion, normal inflammatory markers and no indication of a problem on imaging studies – the so-called uncomplicated TKA. These patients are the subject of this chapter.

Persistent pain after TKA has been shown to be associated with an exaggerated response to pain. Sullivan [7] developed the Pain Catastrophizing Scale (PCS), in order to quantify patient’s negative or exaggerated orientation to pain. It is a 13-item self-reported scale from 0 to 4 and has three different categories: rumination (tendency to focus excessively on pain sensations), magnification (tendency to exaggerate the threat value of pain sensations) and helplessness (tendency to perceive oneself as being unable to control pain symptoms). Scores range from 0 (no catastrophizing) to 52 (severe catastrophizing). Forsythe observed that patients with persistent pain at 24 months after TKA had a significantly higher preoperative PCS, suggesting a psychosocial explanation of post-operative pain [8]. PCS scores greater than 16 have been shown to be associated with poor WOMAC pain scores 6 months after TKA [7]. The PCS can be used as a simple preoperative screening tool to identify the pain responsiveness of patients, and those with higher scores can be offered behavioural therapies to improve their ability to cope with pain. Whilst this has been shown to improve PCS scores, there has been no study published to confirm this helps in patients undergoing TKA.

The constant nociceptive input from an inflamed joint leads to sensitisation of the central and peripheral nervous system to pain. Pain at rest is mediated by both central and peripheral sensitisation, whereas pain on movements is mediated by peripheral sensitisation. Patients with pain at rest having poor pain relief after TKA are easily explained by central sensitisation [9]. Neuronal sensitisation can be controlled by reducing the nociceptive input through medications to reduce joint inflammation before surgery. Pre-emptive analgesia before surgery can play a major role in prevention of establishment of central sensitisation after surgery.

Whilst Scott et al. found younger age at the time of surgery to be associated with higher satisfaction, younger age has also been shown to be associated with persistent pain after TKA. Singh et al. reported a higher incidence of moderate to severe pain 2 and 5 years after TKA in patients who were younger than 60 years at the time of surgery [10]. In a cohort studied by Elson, the incidence of painful TKA was 17 % in patients younger than 60 years as against 6 % in the age group of 60–70 years and 4 % in patients older than 70 years [11].

Controversy exists regarding the effect of gender on the incidence of pain after TKA. Results from studies conducted by Ritter et al. and Singh et al. point towards an association between female sex and persistent pain after TKA [10, 12]. However, Elson et al. and Roth failed to detect any significant difference among men and women in terms of pain after TKA [11, 13].

The classical indication for a TKA has been pain in the presence of severe osteoarthritic changes on radiographs. Polkowsky et al. retrospectively analysed the preoperative radiographs of 49 uncomplicated painful TKA patients and graded the severity of osteoarthritis according to the Kellgren and Lawrence classification. They detected a 49 % incidence of early osteoarthritis in patients with an uncomplicated painful TKA [14].

Hence, identification of the extent to which non-organic factors contribute to the overall pain response is crucial before surgery. The patient may be directed to appropriate cognitive and ancillary therapies in order to correct the underlying factors which would help improve the satisfaction from surgery, especially pain relief. Given that gender, age and osteoarthritis severity affect the incidence of persistent pain following a TKA, it would be prudent to consider these factors when deciding whether to offer surgery.