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To determine if Patient Acceptable Symptom State (PASS), a single-item deterministic binary measure of pain and function outcome satisfaction leads to better differentiation of outcome classification versus latent class analysis probability-based outcome subgroups one-year following knee arthroplasty (KA).We used data from KASTPain, a one-year no-effect multicenter randomized clinical trial of participants with KA along with prior work that developed and externally validated good and poor outcome trajectories. Confirmatory latent class analyses were conducted on two exemplar outcome measures (EQ VAS single-item self-rated health and 4-Item pain ratings) and compared to PASS scores. Separation of trajectories were used to compare good and poor latent class self-rated health/4-item pain trajectories and PASS score trajectories.Prevalence rates for poor outcomes were 10% for self-rated health and 20% for 4-item pain and PASS. Probabilistic latent class derived classifications of self-rated health and 4-item pain outcomes outperformed PASS in separating growth trajectories. The effect size point estimates for 12-month 4-item pain scale score separation was approximately 3 times larger for latent class analyses as compared to PASS.When used for outcome classification, observed PASS scores consistently underperform relative to probabilistic latent class-derived subgroups of pain and self-rated health outcome. PASS is a weak substitute for probabilistic classification of other PROMs of KA outcome. Clinicians and researchers should rely on latent class analyses over PASS to differentiate between outcome subgroups following KA.

Nishida and colleagues conducted a Phase III placebo-controlled repeated knee injection study on persons with radiographically confirmed symptomatic knee osteoarthritis (1). This design allows for the determination of true effects of the active ingredient (diclofenac etalhyaluronate) over that attributable to placebo (contextual) injection effects and non-specific effects (2). My comments on the trial relate to three issues.

Profiling recovery following knee replacement (KR) is a focus of substantial research interest because KR surgery has become one of the most common major surgical procedures. In the United States, for example, approximately one million KRs are performed annually. Additionally, there is substantial clinical practice and research interest in the study of poor pain outcome and predictors of poor pain outcome following KR.

Objective Prognostic estimates for knee osteoarthritis worsening over the full disease spectrum have not been reported. Osteoarthritis Initiative data were used to determine the association between knee radiographic osteoarthritis worsening and future knee pain and function. Methods Yearly data over a 5-year period were analyzed. Outcome measures were the Western Ontario and McMaster Universities Osteoarthritis Index and the Knee Injury and Osteoarthritis Outcome Score pain and symptoms scales. Knees were grouped based on whether yearly Kellgren/Lawrence (K/L) grades worsened. Associations of yearly K/L worsening with knee pain, symptoms, or function scores at the end of the year and with lagged outcomes observed at least 1 year after worsening were assessed using linear models with generalized estimating equations. Results A total of 25,932 knee-years of observations were examined in the primary analysis. For knees with yearly K/L worsening, all outcome scores were significantly worse (P values from 0.02 to

Extensive variation in patients’ characteristics and in surgical rates for patients undergoing a variety of procedures has been well documented. For example, a substantial literature supports the presence of geographic(1), racial and ethnic disparities in total knee arthroplasty (TKA)(2). High rates of variation are not isolated to TKA and have been found for multiple surgical procedures(3). Lawson and colleagues(3), among others(4) have suggested that high variations in surgery rates are likely attributable, at least in part, to either under- or over-utilization. Attempts to quantify the extent of overuse or underuse of a medical procedure require the use of appropriateness criteria to judge indications for the procedure. The RAND-UCLA Appropriateness Method has been used extensively in the US and elsewhere(3;5) to determine the extent of over- or under-utilization of a variety of procedures including bariatric surgery(6), hysterectomy(7), and TKA(8). We used appropriateness criteria for TKA developed by Escobar and colleagues(8) and described in a prior publication(9), to study utilization of TKA. To our knowledge, this will be the first study of TKA appropriateness conducted in the US. We used variables(9) in the Osteoarthritis Initiative dataset(10) to reflect the appropriateness classification system used by Escobar and colleagues(8). We calculated prevalence rates for 175 patients undergoing isolated TKA in OAI and found a rate of 44.0% (95%CI= 37, 51) for classifications of appropriate, 21.7% (95%CI = 16, 28) for inconclusive classifications and 34.3% (95%CI =27, 41) for inappropriate classifications. The purpose of the current study was to determine if outcomes following TKA vary for the three classification groups(8). Outcome measurement in TKA can be conceptualized either as a journey, that is, change in outcome score over time, or as a destination, the outcome score the person ends up with(11). Both are important. The journey captures the magnitude of improvement (or worsening) while the destination describes the extent to which pain and functional status at a later point in time is acceptable to the patient. We hypothesized that subjects classified as inappropriate would have smaller changes in pain and function (i.e., a shorter journey) following surgery as compared to persons classified as inconclusive or appropriate for TKA(12). In regard to the destination, because the OAI data does not report Patient Acceptable Symptom State (PASS) measures(13;14), we were unable to compare groups on PASS. However, pre-operative scores are powerful predictors of post-operative status(15-17) such that persons with less pain and better function prior to surgery should have less pain and better function after surgery compared to more severely involved patients. We therefore hypothesized that the one- and two-year post-operative destination outcome scores would be better (i.e. less pain and better function) for persons classified as inappropriate as compared to the other two groups.

Several recent high-profile publications have described the dramatic growth in utilization of total knee arthroplasty (TKA) in the United States (1–4). Between 1991 and 2010, for example, the annual volume of TKA surgeries among Medicare beneficiaries increased 161.5% and per capita utilization increased 99.2% over the same period (1). Some have suggested that TKA is over-utilized (2) or that over-utilization may be one factor explaining large per capita increases in TKA surgery (1). Cram and colleagues (1) contend that recent growth in TKA utilization is likely due both to an increase in utilization of a highly effective procedure and over-utilization of a procedure that is highly reliant on subjective criteria. Any determination of the extent to which TKA surgery is appropriate or inappropriate requires the use of valid appropriateness criteria. These criteria, as applied to patients undergoing TKA, to our knowledge, have not been formally developed or studied in the US but have been developed in other countries (5–8). The most commonly recommended approach for establishing appropriateness criteria for elective surgical procedures is the RAND/UCLA method (9–11). First, a systematic literature review of risks, benefits and indications for the procedure is conducted. Second, an extensive and mutually exclusive set of clinical scenarios (typically numbering in the hundreds) are written to capture the gamut of potential patient scenarios reflecting all potentially important clinical indications. Third, an expert panel is formed to conduct a modified Delphi survey to classify each scenario as appropriate, inconclusive or inappropriate for the procedure. A rating of “appropriate” indicates the expected benefits of the procedure outweigh the expected harms to the extent that the procedure is justified. A rating of “inconclusive” indicates either that the expected benefits and harms are roughly equal or that a lack of consensus among panel members was found. An “inappropriate” rating indicates the expected harms outweigh the expected benefits. The most extensively studied RAND/UCLA-based appropriateness algorithm for TKA is the approach developed in Spain by Escobar and colleagues (5;12–15). The authors conducted a systematic review of TKA evidence related to indications, effectiveness, and risks and used this evidence to develop 624 clinical scenarios based on the following literature-based key variables: symptom behavior, functional status, extent and location of radiographic arthritis, age, knee joint mobility and stability, and prior history of surgical and non-surgical treatment. A modified Delphi survey approach was used with two independent national panels (n=11 each) of arthroplasty surgeons (n=18) and physiatrists or rheumatologists (n=4). Reliability of recommendations between the two panels was found to be high (Weighted Kappa = 0.75) for judging whether TKA for each scenario was judged to be appropriate, inappropriate or inconclusive. A subsequent study of 775 TKA patients judged as appropriate based on the appropriateness criteria (5) demonstrated the largest WOMAC Scale improvements 6 months following surgery and patients judged as inappropriate had the smallest improvements (14). Ghomrawi and colleagues contend that appropriateness criteria like those developed by Escobar and colleagues, are among the most powerful tools for improving quality of care and controlling costs (2). Because studies in other countries reported that 60% to 80% of arthroplasty procedures were found to be appropriate, Ghomrawi et al suggested that similar over-utilization in TKA was possible in the US. Given that no appropriateness criteria for TKA have been developed in the US, we used a modified version of the Escobar et al appropriateness criteria to make an initial approximation of the proportion of knee arthroplasties that may be inappropriate in the US. While the Escobar et al system was not designed for US patients, we contend that the key criteria used in the system (i.e., pain and functional status, extent of radiographic arthritis, age and knee joint impairment) are likely among the most important criteria for US patients as well (16). Our purpose was to use a modified version of the Escobar et al (5) appropriateness criteria to estimate the proportion of TKA procedures classified as appropriate, inconclusive and inappropriate. We hypothesized that the prevalence rate of TKAs judged to be inappropriate would be similar to prior reports (11;13;14) and approximate 20%.

Objective To determine the trajectories of preoperative worsening and postoperative recovery for both the index knee and the contralateral knee of patients undergoing knee replacement surgery. Methods Of the 4,796 subjects in the Osteoarthritis Initiative cohort study database, we examined 5-year data from 177 patients who underwent isolated unilateral knee replacement surgery and no other joint replacement surgery. Patient-reported outcomes captured domains defined by the International Classification of Functioning, Disability, and Health. Domains of knee structure and function, activity limitation, and participation restriction were examined using growth-curve modeling over 5-year periods prior to and following surgery. Results Preoperative worsening of the index knee was substantial in all domains of knee impairment, activity limitation, and societal participation. Pain intensity worsened only slightly from 5 years to 2.5 years prior to surgery, but worsened by ∼2 points (0–10-point scale) during the 2.5 years prior to surgery. Trajectories of improvement following surgery varied depending on the outcome measure. The contralateral knee also changed over time, such that by ∼2 years following surgery, pain was worse and by 3 years, activity limitation was worse in the contralateral knee as compared to the index knee. Conclusion Patients who elect to undergo knee replacement surgery demonstrate perioperative trajectories of change that influence most health domains for both the index knee and the contralateral knee. After a period of no change, escalation of pain and worsening functioning in the index knee begins ∼2.5 years prior to surgery, which may be a key trigger for surgery.

Objective The impact of knee arthroplasty on body weight has not been fully explored. Clinically important weight gain following knee arthroplasty would pose potentially important health risks. Methods We used one of the largest US-based knee arthroplasty registries and a population-based control sample from the same geographic region to determine whether knee arthroplasty increases the risk of clinically important weight gain of ≥5% of baseline body weight over a 5-year postoperative period. Results Of the persons in the knee arthroplasty sample, 30.0% gained ≥5% of baseline body weight 5 years following surgery as compared to 19.7% of the control sample. The multivariable-adjusted (age, sex, body mass index, education, comorbidity, and presurgical weight change) odds ratio (OR) was 1.6 (95% confidence interval [95% CI] 1.2–2.2) in persons with knee arthroplasty as compared to the control sample. Additional arthroplasty procedures during followup further increased the risk for weight gain (OR 2.1, 95% CI 1.4–3.1) relative to the control sample. Specifically, among patients with knee arthroplasty, younger patients and those who lost greater amounts of weight in the 5-year preoperative period were at greater risk for clinically important weight gain. Conclusion Patients who undergo knee arthroplasty are at an increased risk of clinically important weight gain following surgery. The findings potentially have broad implications to multiple members of the health care team. Future research should develop weight loss/maintenance interventions particularly for younger patients who have lost a substantial amount of weight prior to surgery, as they are most at risk for substantial postsurgical weight gain.

Osteoarthritis (OA) of the knee has multiple causes but one of the more powerful risk factors for OA onset and progression is excessive body weight1,2. The Framingham study, for example, reported that women who lost at least 5kg had a 50% reduction in the odds of developing symptomatic knee OA3. Given the high costs and high prevalence of knee OA, many researchers have focused on attempts to identify interventions that reduce body weight of persons with OA who are overweight or obese4-10. A meta analysis that examined the effects of various approaches to weight reduction with or without co-interventions for persons with symptomatic knee OA found that a weight reduction on the order of a 5% reduction of body weight was associated with insignificant reductions in knee pain but significant though small improvements in self reported functional status.6 Christensen and colleagues also reported a dose-response effect such that the extent of weight reduction was proportional to the extent of functional improvement. In recently published trials, weight reduction strategies leading to losses approximating 10% or more of body weight have resulted in more substantial reductions in pain and improved function4,7,10. In a recently published cohort study of 44 persons undergoing gastric surgery for severe obesity, the average reduction in body weight from baseline to 6-months following surgery was 20.2%11. Average WOMAC Pain and Physical Function scores were reduced by 50% or more. These data, in combination, suggest that weight reduction and improvements in pain and functional status may be proportional and respond in a dose-response manner. Several trials have examined the influences of weight loss on pain and function and we found one cohort study that examined effects of body weight gain on pain or functional status12. If a dose-response relationship exists between body weight changes and corresponding changes in pain and function for persons with symptomatic knee OA, one would expect that body weight gains may also be associated with proportional increases in pain and worsening functional status. We found no studies that determined if a dose-response relationship existed between body weight changes, both gains and losses, and changes in knee related pain and functional status in a large sample of persons with symptomatic knee osteoarthritis. Trial evidence suggests that weight reduction of at least 5% of body weight would lead to improved function and that weight reductions of 10% or more would lead to greater reductions in pain and substantially improved function. Recommendations based on trial findings on persons with knee OA are similar to federal government-based recommendations for weight reduction to optimize health.13,14 Participants in weight loss trials receive extensive attention and training during the trial and it is unclear whether persons in the community who are not part of a weight loss trial and who undergo similar amounts of weight reduction also experience similar changes in pain and function. It also is unknown whether persons who gain weight actually experience worse pain and function and whether this pain and functional loss is proportional to the amount of weight gained. Knowing whether persons in the community report proportionate reductions (or increases) in pain and function following changes in body weight would equip clinicians with additional evidence-based information to aid in managing patients with knee OA. The purpose of our longitudinal cohort study was to determine if a dose-response relationship exists between extent of weight changes (including both weight reduction and weight gain) and extent of changes in self-reported function-related pain and functional status.