During the past decade, increasing emphasis has been given to the outcome of medical treatment, in terms of the real and perceived success of medical interventions in achieving pretreatment goals. As part of this process, the patient’s perspective is being considered as an essential component of the evaluation of treatment. This shift in emphasis is part recognition that, to a significant extent, patients’ expectations determine their assessment of the success of any treatment plan. Moreover, patients’ levels of satisfaction with their own medical care generates much of the demand for expensive procedures and claims for monetary compensation through the legal system. Despite increasing recognition of the importance of patients’ assessments of their medical care, the success of most orthopaedic procedures remains determined solely by criteria established and graded by surgeons after interviews with patients. 22 However, previous studies have shown that patients’ goals and expectations of orthopaedic treatment are highly variable, depending on the age, diagnosis, and lifestyle of each individual. 12,21
In the field of total joint replacement, patients’ expectations have been shown to strongly influence postoperative outcome. 12,21 Moreover, because these procedures are done for pain relief and restoration of joint function, the goals of individual patients will differ with respect to postoperative function and activity. Nonetheless, to a considerable extent, these goals will determine whether the knee replacement was successful, whether the patient thinks that he or she has significant residual disability, and whether, at some point in the future, symptoms related to knee function will cause the patient to seek additional treatment.
In the past, the importance of functional assessment after total knee arthroplasty has been well-recognized and has led to the creation of standard instruments to assess the outcome of this operation. 2,6,7,14,15,17,23,28 The most popular of these instruments have been created by the Hospital for Special Surgery and the American Knee Society, and assess patients’ pain and function after total knee arthroplasty. 14,15 However, these scales are designed to be physician-driven and only assess knee function in terms of the patient’s ability to walk and climb stairs without consideration of functional and recreational activities of importance to each patient or activities that place greater biomechanical demands on the lower extremities (kneeling and carrying loads).
Ideally, evaluation of any medical intervention would be customized to the demands and expectations of each patient. 4,29 Individualized functional assessment of total knee arthroplasty could be accomplished by emphasizing activities that the individual patient does frequently and perceives as being important. Such an evaluation also could be useful in assessing the indications for total knee arthroplasty in comparison with less invasive treatments, including unicompartmental arthroplasty and tibial osteotomies. This information also may help to estimate how much of a patient’s functional deficit is attributable to limitations of the knee prosthesis, and could lead to a rational basis for the development and use of new and improved prosthetic designs.
The purpose of the current study was to develop a method of assessing the functional outcome of total knee replacement and to survey the knee replacement population. The survey was done to define the functional demands of each patient in terms of their participation in specific activities, the perceived importance of those activities, and the limitations in knee function that each patient perceives after knee replacement.
MATERIALS AND METHODS
Development of the Knee Function Survey Instrument
A Knee Function Survey Instrument was developed in two phases. After approval was received from the Institutional Review Board of the authors’ institution, interviews were conducted with patients who had total knee replacements, surgeons who did knee replacement procedures, and physical therapists who worked with patients after this procedure. Information was collected documenting all of the functional activities done by each patient who had a total knee replacement, the importance of each activity to the patient, and the activities that each patient thought were limited by his or her joint replacement. Based on this information, a survey instrument was created consisting of more than 100 multiple-choice questions. Activities were divided into three categories: (1) Baseline activities were defined as fundamental activities of daily living that required knee function, and included walking, stair-climbing, sitting, foot care, bathing, and car travel; (2) Advanced activities included kneeling, squatting, moving laterally, turning and cutting, and carrying loads (a bag of groceries). These activities were done routinely by many patients but required greater strength, control, and range of motion (ROM); and (3) Recreational activities and exercises consisting of 12 activities, including stretching, stationary biking, leg strengthening, swimming, golfing, tennis, cross-country skiing, downhill skiing, dancing, gardening, sexual activity, and running.
Copies of the pilot questionnaire were sent to a selected group of 40 active patients who were at least 1 year after knee replacement. Ten of these patients were recommended by each of four joint replacement surgeons from the authors’ institution. Because one of these patients declined to participate, 39 patients were included in the pilot study. Based on the responses to the pilot study, the length of the survey instrument was reduced. Some questions about easy activities remained in the questionnaire to establish a floor, and some questions about extremely challenging activities remained to eliminate any ceiling effect. The final version of the survey instrument consisted of 55 questions, including 13 items evaluating patient satisfaction, activity level, pain, and other symptoms, 17 items assessing activities of daily living, and 16 items assessing other exercise, sports, movement and lifestyle activities at three levels (importance, frequency, and bother).
Development of a Knee Function Score
To analyze the information from the completed questionnaires, a scoring system was developed (Appendix 1). For each activity, the patient’s activity score was calculated as the product of the frequency of participation, the perceived importance of the activity, and the patient’s ability to do the activity without difficulty. Scores within each group of activities (baseline activities, advanced activities, and recreational activities and exercises) then were averaged to generate subscale activity scores. A composite knee function score also was calculated as the average of the three subscale scores, with the baseline activity score weighted by a factor of 2.
The statistical significance of differences in activity prevalence, composite knee function score and 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.
One hundred seventy-six patients returned completed questionnaires, corresponding to an overall response rate of 48%. Of these patients, 105 (60%) were women (average age, 70 years) and 71 (40%) were men (average age, 71 years). Twenty-four percent of these patients were younger than 65 years, 41% were between the ages of 65 and 75 years, and 35% were older than 75 years.
The average patient did all six of the baseline activities (walking, stair-climbing, bathing, sitting, foot care, and car travel) at least occasionally. One hundred twenty-three patients (70%) participated in all six of these activities, and 11 patients (6%) did four or less activities. Seventy-one patients (40%) regularly did all five of the advanced activities (turning and cutting, moving laterally, kneeling, squatting, and carrying heavy objects), whereas 15 patients (9%) did none of these activities on a regular basis. The average patient participated in six of the 12 possible recreational activities, ranging from two patients (1%) who reported participation in 10 of these activities, to five patients (3%) who participated in only one of these activities.
Participation in specific activities provides additional description of the study participants (Fig 1). More than ⅔ of the patients in the study reported that they did leg strengthening (prevalence, 70%) and stretching exercises (73%) at least occasionally, and 40% of patients did both activities on a regular basis (more than twice per week). Other activities done by patients, at least occasionally, were moving laterally (69%), cutting and turning (74%), kneeling (58%), carrying heavy objects (56%), gardening (57%), and/or riding a stationary exercise bike (51%). Squatting (50%), sexual activities (48%), and dancing (43%) also were common. Thirty-five percent of the patients swam, at least occasionally (9% regularly) and 18% played golf. Interestingly, approximately 10% of the patient population was surprisingly active and occasionally participated in high demand activities. Two patients (10%) who played tennis reported “at least occasional” participation and one patient (7%) participated in cross-country skiing on a regular basis. Surprisingly, 79 patients (45%) reported that they had run at least a few steps since their total knee replacement, and 17 patients (10%) had run distances ranging up to a mile.
Patients also were asked to rate the importance of each activity to them, personally, on a 5-point scale (Fig 2). Expressed as a percentage of patients who actually did each activity, the most important activities to participants were sexual activities (62%), stretching exercises (56%), kneeling (52%), and gardening (50%). Patients also reported that they considered their ability to turn or cut (49%), move laterally (46%), and carry heavy objects (35%) as important, in addition to recreational activities including swimming (36%) and golfing (39%). Fewer participants rated dancing (25%), racquet sports (17%), stationary biking (14%), or cross-country skiing (8%) as important.
Limitations in Doing Activities
According to the responses to the survey, many patients reported that their knee performed completely normally, without symptoms attributable to the knee replacement (Fig 3). In terms of specific activities, more than ½ of the patient group experienced normal knee function when doing the following activities: swimming (77%), sexual activities (70%), golf (65%), stationary biking (64%), and stretching exercises (61%). Almost as many patients reported that they could dance (61%), do leg strengthening exercises (60%), and carry heavy objects (59%); however, fewer patients (46%) could garden without difficulty (Fig 3). In terms of basic knee functions, 57% of patients experienced no difficulty with moving laterally and 52% could turn and cut; however, patients could not kneel (72%) or squat (75%) without some knee symptoms. Of the small subset of patients who participated in sporting activities, more than ½ experienced no knee symptoms when participating in golf (65%), racquet sports (56%), and cross-country skiing (58%); however, patients reporting significant difficulty ranged from 5% (swimming) to 30% (downhill skiing).
Relatively few patients reported that their artificial knee caused moderate to severe difficulty in doing routine exercises: swimming (5%), stationary biking (15%), leg strengthening (17%), stretching exercises (11%), sexual activities (14%), dancing (12%), or moving laterally (15%). However, a dramatic increase was observed in the prevalence of knee symptoms when patients were asked about activities that placed greater loads on the extremity (carrying heavy shopping bags, 20%), or demanded increased knee flexion (gardening [26%], kneeling [47%], and squatting [42%]).
Knee Function Scores
The average value of the composite knee function scores for all activities was 5.7 ± 1.6 points (range, 1.0–10.0 points) for all patients in the study. For the 71 men, the average composite score was 5.7 ± 1.8 points (range, 1.3–10.0 points) compared with 5.6 ± 1.3 points (range, 1.0–8.3 points) for the 105 women (p = .71).
There was no overall correlation between the age of the patients and the average composite score (R2 = 0.01). However, patients younger than 75 years had higher scores than patients older than 75 years (p = 0.03). Patients younger than 65 years (n = 25) had an average composite score of 6.0 ± 2.0 points, compared with 5.4 ± 1.2 for patients between 65 and 75 years (n = 41) and 5.9 ± 1.3 for patients older than 75 years (n = 35).
The number of minutes that a patient could walk continuously did not correlate with the patient’s composite knee function score (R2 < 0.5). Walking ability, as described by the questions in the Total Knee Function Questionnaire (Appendix 2), correlated significantly with the composite score (R2 = 0.8, p < 0.0001). The average composite score of the 118 patients who reported that they could walk more than 15 minutes was 5.9 ± 1.6 points (range, 1.3–10.0 points) compared with only 4.9 ± 1.6 points for patients who could walk for less than 15 minutes. Patients who could walk for more than 15 minutes and also reported unlimited ability in climbing stairs (n = 46) had an average composite score of 6.7 ± 1.3 points (range, 4.6–10.0 points).
One hundred forty-two patients (81%) reported that they were satisfied with their total knee replacement, whereas 33 patients (19%) were not satisfied. Of the 52 patients with unlimited ability to walk and climb stairs, nine (17%) were not satisfied with the functional outcome of their knee replacement. Conversely, 72% (13 of 18) of sedentary patients were satisfied with their total knee replacement, even though they could walk for less than 5 minutes at a time or required a walking aid for ambulation. However, patient satisfaction with knee function after total knee replacement did not correlate with composite subscale scores for walking and stair-climbing (p = .70).
When asked to compare their preoperative and postoperative levels of activity, 20% of patients reported that they were less active now than before their operation, 24% stated that their activity level was unchanged, and 56% reported that they now were more active.
The current study shows that many patients are active after total knee arthroplasty and participate in a diverse range of activities. Many of the patients enrolled in this study regularly participated in therapeutic activities, including swimming, stationary biking, and stretching exercises and leg strengthening routines. Despite increasing age, many patients also participated in a broad range of recreational activities on a regular basis, even though many of these activities, such as gardening, squatting, dancing, kneeling, and carrying heavy items, impose significant loads on the knee. Ten percent of patients also played golf at least occasionally, and 2% played tennis and/or cross-country skied. Even more remarkable was the fact that 10% of the patients had run distances of up to a mile at least once since their total knee replacement.
One of the major strengths of the questionnaire used in this study was the inclusion of items relating to the importance of specific functional activities to the patient. 2,11,29 Moreover, because of the self-reporting format of this instrument, each patient was allowed to report the personal importance of and their frequency of participation in a broad range of activities of graduated difficulty. The responses elicited indicate that many diverse activities are important to patients despite their knee replacement. Many patients cited therapeutic activities such as swimming, stationary biking, leg strengthening, and stretching as being important (Fig 2). A surprising number of patients valued activities such as kneeling, gardening, carrying heavy objects, squatting, dancing, and golf. More vigorous sporting activities, including cross-country skiing and tennis, were important to far fewer patients in the population studied. There was a high correlation between the importance of an activity to the patient and the frequency of their participation (Fig 4). This suggests either that knee replacement allows many patients to do activities that they consider important, or that patients do what they consider important regardless of the functional status of their knees.
An important conclusion of this study is that, not withstanding the success of knee replacement in relieving pain, many patients still experience significant difficulty in doing activities that they regard as important, including gardening and kneeling (Fig 5). More than ¾ of patients who squatted and kneeled reported limitations. Participation in therapeutic activities, including stretching and leg strengthening exercises also was limited by knee function, and more than ⅓ of the patients reported that their replaced knee limited their recreation in activities ranging from dancing (39%) to racquet sports (44%) to golf (35%). The percentage of patients who experienced limitations in other challenging activities ranged from 41% (carrying heavy objects) to 75% (squatting) (Fig 6). These observations lend support to the conclusion that although knee replacement does not prevent patients from doing activities they consider important, the procedure, nonetheless, does not restore the ease associated with normal knee function. 3,13,20
Great variability was observed in the knee function of the patients with knee replacements who participated in this study. A broad continuum was found across all degrees of activity, rather than a categorical distinction between sedentary and active patients. This variability is shown by the wide range of aggregate knee function scores that ranged from 1.0 to 10.0 across the population studied, and the wide range of scores in each subscale of the knee function survey.
To the authors’ knowledge, this is the first methodical examination of the various functional abilities, priorities, and limitations of patients after total knee replacement. In the past, some important points may have been neglected in an attempt to simplify the definition of function after total knee replacement. This may be because the traditional functional assessment tools were not designed to assess the growing prevalence of younger and more active patients in the total knee replacement population. 5,8,26 The relevance of assessment tools that ignore the functional capacity of patients in doing prevalent and important activities is questionable. Although the knee rating scores of the Knee Society 14 and Hospital for Special Surgery 15,21 may accurately measure components of knee function that the surgeon considers important (ROM), the relevance of these parameters to the patient and his or her priorities is unknown. Furthermore, these rating scales assume that knee function may be gauged by the patients’ ability to walk and climb stairs even though other activities may impose different loads and motions on the knee. Moreover, this study shows that activities other than walking and stair-climbing often embody the most important elements of the knee function sought by the patient. The survey instrument used in this study was designed to describe more fully knee function after total knee replacement by addressing the wide range of activities prevalent among patients who had total knee replacement. Using this information, it is possible to assess the performance of this therapeutic intervention in addressing the perceived needs and priorities of individual patients.
These results suggest that conventional questionnaires and scoring systems may be missing important information about knee function in the patient who had joint replacement. It is clear that patients with knee replacements participate in different activities and thus it is not possible to accurately portray function after these procedures in terms of the patient’s ability to do one or two activities nominated, a priori, by the surgeon. In addition, comprehensive examination of the functional activities of patients after total knee replacement indicates that the ability of patients in doing functional activities is highly dependent on the specific activity. 10,20 In view of these compounding factors, many activities in addition to walking and stair-climbing must be considered to describe the functional demands and expectations of patients after total knee replacement. An additional consequence of the survey approach is that patients have more opportunity to evaluate the success of knee arthroplasty in fulfilling their personal expectations. Not surprisingly, it was found that knee arthroplasty does not seem to restore as much function as previous, less comprehensive studies, may have suggested. 1,9,11,16,18,19,24,25,27
The current study has some obvious limitations, including those inherent to any work based on responses to self-administered questionnaires. The most significant of these was the fact that only ½ of the patients who were sent the questionnaire completed and returned it. Although this rate of return probably is better than average for survey instruments of this type, it raises the question of the absolute validity of the conclusions that have been made. Differences between responders and nonresponders may contribute to a self-selection bias, although none of the demographic variables that could be assessed indicated any significant difference between patients who completed the survey and patients who did not complete the survey. It is true that patients who are working full-time may have less time to participate in the study compared with patients who are retired. Conversely, patients who are not active may have been discouraged by the many questions addressing challenging activities, and may have been disinclined to participate. This methodology also relies on the patients’ abilities to accurately report their status and their frequency of participation in functional activities. Even among patients who did return a completed packet, there is no way of knowing which patients unintentionally may have inflated or deflated their functional status.
This study also shows that age, gender, and walking ability correlate poorly with the functional status of the patient. Additional study is required to identify the characteristics of the patients who are likely to place greater demands on their prostheses, patients who will have higher rates of wear, and patients who will benefit from prostheses designed to increase mobility while still providing protection against early loosening and failure. Additional work also is needed to compare the responses reported in this study with those of healthy control subjects to gauge the effect of surgery on normal knee function as distinct from the influence of age alone.
The current study has shown that patients who had knee replacement participate in a diverse range of activities. Consequently, conventional outcome instruments that assess patient function on the basis of walking and stair-climbing can, at best, only provide a limited insight into the patient’s ability to do those activities. However, the activities that determine the success of the procedure to the patient, and even its ultimate longevity, are unlikely to be represented by the limited snapshot provided by walking and stair-climbing activities. The study does confirm that, for most patients, knee replacement successfully restores a significant degree of function, especially in doing the basic, low-demand activities of daily living. However, these patients also report significant limitations in doing some activities that are more physically demanding but are nonetheless important. This suggests that function after knee replacement may not be as satisfactory, to the patient, as previous studies have suggested.
The authors thank Dr. Sharon Olsen for critique and analysis of this work. The authors also thank the following surgeons for assistance and suggestions in the development of the Knee Function Questionnaire: Brian Parsley, MD, Hugh Tullos, MD, William Bryan, MD, David Lionberger, MD, Anthony Hedley, MD, Joseph McCarthy, MD, Robert Bourne, MD, Aaron Hoffmann, MD, Lawrence Dorr, MD, Clifford Colwell, MD, Glenn Landon, MD, and Michael Huo, MD.
Appendix 1. Knee Scoring System
1Frequency score ranges from 0 to 50 (0 = never)
2Importance score ranges from 1 to 5 (1 = not important)
3Bother score ranges from −2 to 2 (2 = no bother) MATH
Appendix 2. Total Knee Function Questionnaire
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Richard S. Laskin, MD—Guest Editor