Patient satisfaction is the ultimate goal of all orthopaedic procedures. However, total joint arthroplasty is performed in the face of degeneration of the normal articulation, often at the conclusion of a protracted, painful, and ultimately unsuccessful campaign to preserve the natural joint. Against this backdrop, satisfaction with the outcome of this final stage of treatment may be defined in many different ways, with widely varying results. Previous studies have demonstrated that, to an important extent, the expectations and perceptions of individual patients may define whether the outcome of knee replacement is successful, whether some degree of residual deficit is disabling, and whether, at some point in the future, symptoms related to knee function will cause the patient to seek additional treatment.4-7 These studies agree the primary aim of knee replacement is relief of pain, and in this respect, arthroplasty is overwhelmingly successful. However, as this goal is achieved early in the postoperative period, patients may revise their priorities and define the success of their treatment in terms of secondary goals, principally restoration of joint function. This may account for the findings of the National Institutes of Health Consensus panel, and numerous clinical reviews, that only 85% of patients are satisfied with their outcome after knee replacement.1,2,13-15,29 Moreover, though patients and surgeons agree that knee replacement should at least enable patients to perform low-demand activities, patients increasingly expect advances in surgical techniques and implant designs to enable them to return to their original functional status without pain or impairment.20,21,31
Thus, satisfaction with the outcome of total knee replacement is expected to depend on a combination of several factors, weighted according to the demands and expectations of each individual.10,12,18,19,21 Undoubtedly, patient satisfaction must be influenced by the extent to which the procedure relieves the patient's original symptoms and restores the normal motion of the knee.15,23 However, recent research has demonstrated that subjective factors also affect how patients internalize their symptoms and function.3,8,11,28 Consequently, each patient's objective status may be less important than the degree to which the patient is conscious of their artificial joint,9 or the belief that their treatment was successful in providing the outcome they envisioned before surgery.21
We undertook the following study to determine which factors contributing to patient satisfaction with total knee replacement, and their relative importance. In analyzing the role of individual factors, our secondary goal was to classify predictors of patient satisfaction and dissatisfaction as indicators of: (1) residual symptoms; (2) the functional capacity of the knee after TKR; (3) the extent to which normal knee function was regained after TKR; and (4) the degree to which the outcome of TKR met each patient's expectations.
MATERIALS AND METHODS
To study factors associated with patient satisfaction after total knee replacement, we developed and validated a self-administered survey instrument called the Total Knee Function Questionnaire (TKFQ), which is described in detail in previous publications.25,30 This instrument consists of 55 multiple choice questions relating to symptoms and functional abilities involving the knee, including items relating to each patient's degree of overall satisfaction with their knee replacement. Items within the instrument explored each patient's subjective appraisal of the functional outcome of their knee replacement, the frequency and severity of clinical symptoms involving their replaced knee, and the extent to which their knee replacement fulfilled their expectations. On the basis of responses obtained from patients after primary knee replacement, we were able to examine the association between individual responses relating to knee function, residual symptoms, and patient expectations, and the prevalence of responses indicative of patients' satisfaction with the outcome of their joint replacement. This analysis was then extended to develop a multivariate model to predict which patients would be satisfied and dissatisfied with the outcome of knee replacement. Through examination of the variables having the strongest association with patient satisfaction, the relative importance of functional ability, symptomatology, and patient expectations were assessed in qualitative terms.
Data was collected from 253 patients who completed the Total Knee Function Questionnaire (TKFQ), at least one year after primary unilateral TKA. Of these patients, 148 (59%) were women (average age, 67.5 years) and 105 (41%) were men (average age, 69 years). The average age of the study group was 68.1 years (range, 23-90 years). The primary etiology of degenerative joint disease before arthroplasty was osteoarthritis (74% of patients), followed by rheumatoid arthritis and (12%) and prior trauma (9%). In completing this instrument, each patient was asked for responses relating to a comprehensive battery of activities involving the knee. These activities were divided into three categories: (1) baseline activities (17 questions), defined as fundamental activities of daily living that required knee function including walking, stair climbing, sitting, foot care, bathing, and car travel; (2) advanced activities (9 questions), which required greater strength, control and range of motion (ROM), and included kneeling, squatting, moving laterally, turning and cutting, and carrying loads (a bag of groceries); and (3) recreational activities and exercises (16 questions), consisting of 12 activities that included stretching, stationary biking, leg strengthening, swimming, golfing, tennis, cross-country skiing, downhill skiing, dancing, gardening, sexual activity, and running. In considering each of these activities, each patient was asked: (1) whether they performed the activity, and, if so, how frequently; (2) how important was the activity to them, personally; and (3) the extent to which their participation was hindered by the function of their artificial knee.
Additional items evaluated the extent to which knee replacement fulfilled patients' expectations. Patients were also asked the following questions: (1) Does your TKA keep you from doing anything you would like to do? (Y/N); (2) Are you more or less active now than you were before your surgery? (More/Less/Same); (3) Are you as active now as you expected you would be? (Y/N). Each patient's ability to walk was also explored in detail. Patients were asked how long they could walk without stopping, whether they used walking aids, about walking up and downhill, and about walking on even and uneven ground. Each patient was also asked to report symptoms experienced in their operated knee by answering the questions: (1) Do you ever experience swelling or tightness in your knee? (responses: never through to more than once per week, 5 levels); (2) What percentage of the time is your knee stiff? (never through to always [75-100%], 5 levels); (3) How often do you take medication because of pain in your replaced knee? (never through to more than once per day, 5 levels); (4) Does your operated knee feel “normal”? (Y/N). The questionnaire also obtained basic demographic information, overall health status, history of arthritis, and relevant knee history at the time of the survey.
Information from the completed questionnaires relating to each patient's functional ability was incorporated in a scoring system that generated a function score specific to each activity in addition to an overall composite score indicative of each patient's knee function. Scores within each group of activities (baseline activities, advanced activities, and recreational activities and exercises) were then averaged to generate subscale activity scores. Details regarding the derivation of this scoring system have been reported in a previous publication.30
The statistical significance of differences in activity prevalence, TKFQ scores and TKFQ subscale scores by gender, age, and walking ability were assessed using an analysis of variance (ANOVA) test when more than two groups were compared and an unpaired t-test when only two groups were compared. Significant differences were defined as having a p value less than 0.05. To explore factors associated with satisfaction, a univariate logistic model was developed in which satisfaction was expressed dichotomously, by coding patient responses of satisfied and very satisfied equal to 1 and dissatisfied and very dissatisfied equal to 0. Responses of neutral were censored. Independent variables described patient demographics (gender, age, and diagnosis), activity level (number of activities considered important, number of activities done more often than sometimes, change in activity level post surgery, congruence with expected activity level), pain (consumption of analgesic medications), frequency of knee symptoms at followup (swelling, stiffness), difficulty in performing activities involving the affected knee (all activities, important activities, basic activities, exercise activities, and recreational activities), functional ability (ability to perform a battery of activities of daily living) and limitation of enjoyment.
Using the entire sample, a multivariate logistic model was developed to predict patient satisfaction, based on the following criteria: the most accurate prediction of known satisfaction levels, and the most parsimonious model, ie, the model that does not include variables that do not improve prediction of satisfaction. To select the smallest subset of variables best predicting satisfaction, candidate variables were grouped into the following sub-categories: demographics, symptoms, expectation, activity level, functional limitations, and knee symptoms during activities. The variable in each subcategory with the strongest univariate correlation with satisfaction was selected to represent all of the variables in the subcategory. Once the set of candidate variables was selected from all of the subcategories, each variable in the set was entered into the logistic model in the order corresponding to its predictive value. The increase in predictive value was calculated after the addition of each new variable, as expressed by the change in the value of the -2log likelihood statistic. If this increment was statistically significant at the p < 0.05 level, the added variable was retained. If p > 0.05, the next most predictive variable was tested. This procedure was repeated until all potential variables were exhausted. The power of the final model in predicting satisfied and dissatisfied cases was then evaluated. In view of the bivariate distribution of patient responses to questions relating to satisfaction, and the potential for responses from satisfied patients to mask associations within the population of dissatisfied patients, a secondary univariate analysis was performed on the dissatisfied patient group.
Seventy-five percent of the patients reported that they were either satisfied (18%) or very satisfied (57%) with their knee replacement, while 11% reported that they were neutral and 14% reported that they were either dissatisfied (3%) or very dissatisfied (11%) (Fig 1).
Factors associated with a higher proportion of patient satisfaction were age 60 or under at followup (odds ratio = 5.90, p < 0.001), and a knee that felt normal (odds ratio = 3.65, p < 0.001). Of the 53 patients of 60 years of age or younger, 96% reported satisfaction with TKA, compared to 81% in the 60 to 75-year-old group, and 86% of patients older than 75 years. Forty-six percent of dissatisfied patients reported that their knee did not feel normal compared to 20% of satisfied patients (p < 0.0001) (Table 1).
Factors associated with a lower proportion of satisfied patients included an age of 60 to 75 years at followup (odds ratio = 0.43, p = 0.024), knee stiffness at least once per week (odds ratio = 0.17, p < 0.001) (Fig 2), swelling of the affected knee at least once per week (odds ratio = 0.38, p = 0.010) (Fig 3), and use of analgesics at least once per day to treat pain associated with the affected knee (odds ratio = 0.37, p = 0.011). Overall, only 5% of satisfied patients experienced knee stiffness at least once per week compared with 23% of dissatisfied patients. Over one third (36%) of the dissatisfied group also reported that their knee swelled at least once per week compared with 18% of satisfied patients. Finally, 83% of satisfied patients never or rarely take pain medication because of pain in their operated knee compared to 65% of dissatisfied patients (p < 0.0001). In fact, 22% of dissatisfied patients take pain medication once or more per day, compared to 8% for satisfied patients.
There was no correlation between patient satisfaction and gender. There was a correlation (p < 0.001) between patient satisfaction and limitations in performing activities involving the replaced knee, although there was no difference in the number of activities performed by satisfied and dissatisfied patients. One half (50%) of dissatisfied patients reported they were not as active as they expected they would be before the operation compared with 14% for satisfied patients (p < 0.0001) (Fig 4). Similar differences were observed in the proportion of patients who reported they were less active after their knee replacement operation (dissatisfied, 32% versus satisfied, 14%; p = 0.0001), and in the prevalence of patients who reported that their knee kept them from doing activities they wanted to do (dissatisfied, 53% versus satisfied, 33%; p < 0.0001).
There were differences in the difficulty reported by satisfied and dissatisfied patients in performing basic activities of daily living (ADL) such as climbing and descending stairs, getting up from a low couch or chair, and walking up and down a ramp or on an uneven surface. Overall, dissatisfied patients reported at least some difficulty in performing 71% of the ADLs included in the questionnaire compared with 45% of satisfied patients (p < 0.0001). Dissatisfied patients also exhibited lower functional performance with many functional activities including stretching (p = 0.01), leg strengthening exercises (p = 0.0001), turning/pivoting (p = 0.005), moving laterally (p = 0.0003), dancing (p = 0.01), gardening (p = 0.03), and squatting (p = 0.004). Both groups exhibited functional deficits during kneeling. On average, satisfied patients scored 1.8 times higher than dissatisfied patients per activity (Fig 5). Knee function scores were calculated for the activities that each patient identified as personally important. This analysis revealed that dissatisfied patients experienced more difficulty (p = 0.008) and functional deficit (p < 0.0001) than satisfied patients in performing those functional activities of greatest personal importance. However, there was no difference between the satisfied and dissatisfied patients in terms of the number of activities performed (Fig 6).
In developing a multivariate logistic model of patient satisfaction, the following independent variables were initially included: age (odds ratio = 0.43), frequency of knee stiffness (odds ratio = 0.17), knee feels abnormal (odds ratio = 0.27), patient not as active as expected (odds ratio = 0.17), patient less active than before surgery (odds ratio = 0.35), limitation in performing liked activities (odds ratio = 0.42), limitation in performing activities of daily living (odds ratio = 0.21), and patient bothered by symptoms in performing important activities (odds ratio = 0.20) (Table 2). Because many variables in each subgroup were highly correlated, inclusion of only one variable in the subgroup was necessary to explain the contribution of all variables in the subgroup. This was particularly true of all variables describing knee symptoms (pain, swelling, stiffness) and the types of activities that gave rise to bothersome knee symptoms (all activities, important activities, basic activities, exercise activities, and recreational activities).
The logistic model with the greatest predictive accuracy correctly assigned 90% of patients to the satisfied and dissatisfied groups. This model was based on responses to only 6 questions: knee stiffness more than once per week, (relative impact, −0.39); patient is as active as they expected they would be at followup, (relative impact, +0.76); patient's knee bothers them if they perform activities they consider important, (relative impact, −1.35); patient less active after TKA than before TKA, (relative impact, −0.95); medication for knee pain more than once per week, (relative impact, −0.76); age at followup > 75 years, (relative impact, +1.24); or < 60 years, (relative impact, +1.79) (Table 3). Using all of these factors, the logistic model was able to correctly classify 97.3% of satisfied patients, but only 41.2% of dissatisfied patients. Moreover, once the frequency of knee stiffness had been entered into the model, addition of other variables did not improve its ability to correctly predict satisfied patients. Conversely, five variables were required to correctly predict more than 40% of the dissatisfied patients in our study population.
In view of the large difference in the accuracy of our statistical model in correctly identifying satisfied and dissatisfied respondents, a secondary analysis was performed that only considered the responses of patients who were dissatisfied with the outcome of their TKA. This subset of 39 patients was divided into two cohorts: Group 1 (symptoms; 17 patients) consisted of those who had frequent episodes of stiffness, pain or swelling, while all other patients were assigned to Group 2 (no symptoms; 22 patients). Dissatisfied patients without symptoms were older than those with symptoms: 73.7 versus 66.6 years (p < 0.001). The proportion of men and women in both groups was identical. Dissatisfied patients without symptoms were indistinguishable from satisfied patients in terms of their ability to perform functional activities.
Patient satisfaction is becoming increasingly important in defining a successful outcome of surgical intervention. This statement is particularly true of total knee replacement which is performed on an elective basis to restore joint function and eliminate disabling pain. Surgeons are critically aware of variations in the functional outcome of knee replacement, and differences between patients in terms of their satisfaction with the procedure, however, the relationship between outcome and patient satisfaction is clearly multifactorial. Moreover, the relative impact of each factor on patients' evaluation of their functional status remains to be elucidated. This study was undertaken in an attempt to assess the relative importance of functional ability, residual impairment, and subjective expectations, as determinants of satisfaction with the outcome of total knee arthroplasty.
This study has several strengths and limitations. Its primary strength is that the analysis is based on responses to a validated, self-administered survey instrument. The items present in this survey allow us to explore many facets of each patient's expectations, functional abilities, and symptoms at followup, in combination with factors related to satisfaction and dissatisfaction with knee function after TKA. In addition, the data were collected from each patient on a confidential basis, minimizing the patients' concerns that any of the opinions expressed may offend their surgeon or affect their followup care.22 A fundamental limitation of the study is that the data were collected at one time point. Moreover, although we have examined associations between patient satisfaction and other variables, this analysis is unable to prove the role of each factor in causing satisfaction or dissatisfaction after TKA. Nonetheless, this analysis can serve as a valuable source of working hypotheses for prospective studies in the future.
A further shortcoming of our study design is that it depends on completion of a lengthy questionnaire. Previous experience with this survey instrument in our patient population has shown that less than two-thirds of potential respondents return this instrument completed if it is self-administered in the home. This is comparable to reports from other centers.26,27 It is our expectation that those not returning the survey would tend to have less favorable responses26 and so may provide more insight into reasons for dissatisfaction with TKA. As the data collected can only reflect the perceptions of those patients who chose to participate in our study, it is likely that the incidence of patients who are dissatisfied with the procedure is higher than we have reported. Nonetheless, we have no reason to believe that the relative importance of factors affecting satisfaction would be any different in a more complete sample.
The first of the previously explored hypotheses, the impairment hypothesis, holds that patient satisfaction and the mechanical performance of the replaced joint are synonymous, and that dissatisfaction is a reflection of the extent to which the biomechanical function of a patient's joint is abnormal. If this is accepted as being true, it follows that the key to increasing the satisfaction of the patient is to provide devices and procedures that allow normal joint motion and mechanics. However, the impairment hypothesis is not supported by previous reviews,2,8,17 or several key observations derived from the present study. Firstly, we found little correlation between the frequency of activities involving the knee and patients' satisfaction, whereas patients who were dissatisfied had markedly more difficulty in performing almost all activities requiring knee function. This suggests that most patients minimize the impact of residual disability on their lifestyle, and continue to perform the activities they want, despite limitations in the function of their knee post arthroplasty. We also showed that, among patients with no knee symptoms, there was no apparent difference between satisfied and dissatisfied patients in terms of their demographic profile or functional capacity. This suggests that satisfaction with the outcome of total knee replacement has more to do with each patient's subjective perception of their knee function than the biomechanical performance of their knee.
The impairment hypothesis is also inconsistent with the observation that patient satisfaction is lowest in patents between the ages of 60 and 75 years, and highest in those under 60, and intermediate in patients older than 75. If knee function were the primary driver of satisfaction, one would expect that satisfaction would decline with age. Conversely, if the loss of ability after TKA were important, the youngest patients would be least satisfied with their outcome, as previous work has shown that the under 60 age group sustains the larger deficit in comparison with their age and sex-matched peers.25
An alternative hypothesis is that dissatisfaction is generated by disability, and so satisfaction stems from a patients' ability to perform functional activities that they consider important to the extent that they want, without difficulty or recurrence of symptoms. In an earlier study of activities performed by knee replacement patients, we showed that patients attach widely different degrees of importance to activities involving the knee.30 However, many patients attach importance to activities, like kneeling and squatting, which are both biomechanically demanding and indicative of normal knee function. On this basis, it is to be expected that patient satisfaction might be related to the ability of the patient to perform those activities of greatest personal importance, or activities that place highest demands on the knee (or provoke the highest level of discomfort or impairment). This conclusion was supported by the results of the multivariate logistic analysis that showed three factors independently correlated with reduced patient satisfaction were difficulty in performing activities the patient considered important, limitations in performing activities that the patient enjoyed, and limitation in performing activities of daily living.
Many clinicians have observed that, to a large extent, satisfaction and dissatisfaction are products of the mind as much as the body. Consequently, any analysis of patients' subjective assessment of TKA must primarily consider the psychological impact of aging, joint disease, and disability on the patient before and after their joint replacement.9-11,16 This leads to the alternative hypothesis that patient satisfaction with the outcome of TKA depends on the extent to which that outcome meets the patient's expectations, no matter how reasonable or unreasonable they may be. The results of this study do, in fact, show that patients' expectations are highly correlated with satisfaction after total knee replacement. Patient satisfaction was strongly associated with fulfillment of patients' expectations that their activity level, after recovery, would be at least as they expected before surgery. Conversely, patients who were less active than they expected were highly likely to be dissatisfied with the procedure. Almost all questions relating to expectation were predictive of satisfaction and, for this reason, it is not possible to reliably discriminate between alternative spheres of activity in isolating those areas of expectation that were most indicative of subjective outcome.
In practice, a diverse range of factors appear to form the basis of patients' expectations; some relate directly to their joint pathology (eg, knee pain, joint function), while others may be only subjectively connected to the condition of the knee (eg, feelings about aging, self-image). Clearly, the more patients' expectations are based on outcomes not directly connected to joint function, the less likely joint replacement will meet those expectations, and thus, the less likely a patient might regard their outcome as being satisfactory. However, even if it is postulated that reasonable expectations can only be those based on joint function and symptoms, it is unknown whether patients' satisfaction is most predicated on expectations pertaining to all activities involving the knee or key activities that most impact some aspect of each patient's lifestyle.
Although psychological factors have a critical influence on each patient's evaluation of their knee replacement, it remains true that more half of all patients expressing dissatisfaction also failed to achieve asymptomatic knee function at 1 year postoperatively. In this study, we defined recurrence as swelling of the knee or episodes of stiffness more frequently than once per week or daily use of analgesics for relief of knee pain. Overall, approximately ⅔ of patients never or rarely experienced these symptoms at follow-up; however, even among satisfied patients, 18% experienced knee swelling at least once per week. A recurring theme in our analysis of satisfaction and outcome is patients find knee symptoms unacceptable after knee replacement, presumably because their initial reason for undertaking the procedure was symptomatic relief. Thus, the strongest determinants of dissatisfaction at followup were found to be frequency of knee stiffness,24 the perception that the knee felt abnormal, and frequency of medication for knee pain. Clearly, attention to prevention and treatment of symptoms following total knee replacement would likely have the greatest impact on patient satisfaction with the outcome of these procedures.
Our results suggest separate analyses should be performed of satisfied and dissatisfied patients in future work. Although all clinicians recognize that the opinions of patients after surgical treatment is a complex amalgam of relief, regret, hope, and expectation, many surgeons feel most comfortable with a dichotomous assessment of their patients' responses as satisfied or dissatisfied. This method of classification leads to the assumption that satisfaction and dissatisfaction are diametrically opposite states, not just in terms of emotions, but also in terms of the factors and perceptions leading to each state. However, our results demonstrate that patients' responses to the outcome of knee replacement cannot be classified so simply. In reality, many factors seem to lead patients to regard the outcome of their surgery favorably and unfavorably, and the relative importance of each factor may vary with the individual. Moreover, it appears that there is only partial concordance between factors leading patients to be less satisfied with their outcome, and those causing patients to express overt dissatisfaction with the same procedure.
Though unproven, it also seems reasonable to assume that patient's expectations, whether reasonable or irrational, will strongly influence their interpretation of the outcome of their joint replacement procedure, and their ultimate satisfaction. In anticipating a successful outcome from treatment of any chronic degenerative disease, it is natural for the patient to hope their function might be restored to what it was before the onset of their initial symptoms. This hope often supercedes many considerations, including the passage of time, the effects of age, and the extent to which the patient has maintained their health and their fitness despite the disabling effects of their chronic disease. In the face of these hopes, the surgeon must guide patients in helping them formulate reasonable expectations for the outcome of each available treatment option. This suggests that real improvements in patient satisfaction after TKA will be realized once we address patients' preoperative concept of a satisfactory outcome as much as the functional performance of the knee prosthesis itself.
The authors wish to acknowledge the assistance of the following physicians whose patients participated in this study: William J. Bryan, MD, David Edelstein MD, Michael Huo, MD, George Lane, MD, David R. Lionberger, MD, Brian S. Parsley, MD and Hugh S. Tullos, MD (deceased). We also recognize the technical assistance of Ms. Denise Leon and Ms Sheri Wall in preparation of the manuscript.
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