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Summary Objective To determine whether good versus poor outcome trajectories and predictors of poor outcome obtained in a derivation study could be replicated in an independent sample of persons undergoing knee arthroplasty (KA). Methods We used data from TRIO-POPULAR, a prospective cohort study of 926 participants who underwent KA in the United Kingdom. The participants were assessed preoperatively and 6-weeks, 6- and 12-months postoperatively. The Oxford Knee Score was the primary outcome and a variety of pre-operative predictors of outcome were selected. The outcome measure and the predictors were selected to most closely align with a previously published derivation study of good versus poor outcome. Confirmatory two-piece latent class growth curve analyses were used to model outcome and regression was used to identify predictors of outcome class. Results Trajectories for the Oxford Knee Scores from TRIO-POPULAR replicated trajectories for WOMAC Pain and Function scores from the previously published derivation study. Multivariable predictors of poor outcome were pain catastrophizing (odds ratio = 1.125, 95% CI = 1.048, .206, p = 0.001) and comorbidity (odds ratio = 1.134, 95%CI = 1.049, 1.227, p = 0.002. Pain catastrophizing also predicted poor outcome in the derivation study. Conclusions Good and poor outcome trajectories replicated those found in the previously published derivation study. Our model-based method produces stable outcome trajectories despite using data from different countries and participants with substantively different characteristics. Predictors of poor outcome were somewhat inconsistent between the cross-validation and derivation studies. Pain catastrophizing was the only consistent poor outcome predictor.

Objective The assessment of racial differences in pain and function outcome following knee arthroplasty (KA) has received little attention despite very substantial literature exploring a variety of other prognostic factors. The present study was undertaken to determine whether race was associated with KA outcome after accounting for potential confounding factors. Methods We conducted a secondary analysis of a randomized clinical trial of 384 participants with moderate-to-high pain catastrophizing who underwent KA. Preoperative measures included race/ethnicity status as well as a variety of potential confounders, including socioeconomic status, comorbidity, and bodily pain. Outcome measures were Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and function scales as well as performance measures. Linear mixed-effects models compared outcomes over a 1-year follow-up period for African American versus non-African American participants. Results WOMAC pain scores differences for African American versus non-African American participants averaged ~2 points in unadjusted analyses and 1-1.5 points in adjusted analyses. In adjusted analyses, follow-up WOMAC function scores differed by 6 points for African Americans compared to non-African Americans (P = 0.002). Conclusion African Americans generally had worse pain, function, and performance prior to KA and worse scores after surgery, but differences were small and attenuated by ~25-50% after adjustment for potential confounding. Only WOMAC function scores showed clinically important postsurgical differences in adjusted analyses. Clinicians should be aware that after adjustment for potential confounders, African Americans have approximately equivalent outcomes compared to others, with the exception of WOMAC function score.

OBJECTIVES: This study examined ninety-day and one-year postoperative healthcare utilization and costs following total knee arthroplasty (TKA) from the health sector and patient perspectives. DESIGN: This study relied on: 1) patient-reported medical resource utilization data from diaries in the Knee Arthroplasty Pain Coping Skills Training (KASTPain) trial; and 2) Medicare fee schedules. Medicare payments, patient cost-sharing, and patient time costs were estimated. Generalized linear mixed models were used to identify baseline predictors of costs. RESULTS: In the first ninety days following TKA, patients had an average of 29.7 outpatient visits and 6% were hospitalized. Mean total costs during this period summed to $3720, the majority attributed to outpatient visit costs (84%). Over the year following TKA, patients had an average of 48.9 outpatient visits, including 33.2 for physical therapy. About a quarter (24%) of patients were hospitalized. Medical costs were incurred at a decreasing rate, from $2,428 in the first six weeks to $648 in the last six weeks. Mean total medical costs across all patients over the year were $8,930, including $5,328 in outpatient costs. Total costs were positively associated with baseline Charlson comorbidity score (p

Summary Objectives No clinical prediction rules were found for estimating the likelihood of developing incident radiographic tibiofemoral osteoarthritis (OA) with rapid progression. Such a tool would enhance prognostic capability for clinicians and researchers. Design We used two longitudinal datasets to independently derive (Multicenter Osteoarthritis Study) and validate (Osteoarthritis Initiative) a prognostic clinical prediction rule for estimating the probability of incident rapidly progressing radiographic knee OA in the following 4–5 years. Eligible subjects had at least one knee with a Kellgren and Lawrence (K&L) graded tibiofemoral joint of 0 or 1. Several potential risk factors were examined including obesity, age, knee alignment, frequent knee symptoms, contralateral knee OA and knee injury history. Multiple logistic regression was used to identify significant predictors and area under the receiver operating characteristic curve (AUC) was used to assess discrimination. Results A total of 1690 subjects participated in the derivation and 2422 subjects participated in the validation of the clinical prediction rule. The multivariable model displayed good discrimination with AUC of 0.79 in the derivation dataset and 0.81 in the validation dataset. Conclusions Persons with contralateral knee OA, a baseline index knee OA grade of 1, higher body mass index (BMI) and higher baseline Western Ontario and McMaster Universities arthritis index total scores were more likely to develop K&L grade of 3 or 4 within 5 years. Frequent knee symptoms at baseline were not a significant predictor. The prediction rule and nomogram can assist clinicians in estimating the probability of rapidly progressing radiographic knee OA and the nomogram can assist researchers conducting epidemiologic studies and clinical trials.

Summary Objectives We determined the radiographic osteoarthritic worsening rate prior to knee arthroplasty (TKA) and whether this worsening was associated with worsening pain and function as compared to a non-surgical matched sample. Methods We used the Osteoarthritis Initiative 5-year datasets. Extent of knee OA 2 years prior to total knee arthroplasty (TKA) was matched to knees of persons who did not undergo TKA. Western Ontario and McMaster Universities Arthritis Index (WOMAC) Function and Knee injury and Osteoarthritis Outcome Score (KOOS) Pain scales were used to quantify functional deficit and functionally relevant pain respectively. A total of 167 persons with isolated TKA and 300 persons with matched symptomatic knee OA but no TKA were studied. Results During the 2 years prior to TKA, worsening by at least one Kellgren and Lawrence (KL) grade occurred in 27.4% (95% CI = 20.6–34.2) of the surgical knees compared to 6.6% (95% CI = 3.8–9.4) of matched non-surgical knees. Osteoarthritis radiographic progression was strongly associated with WOMAC Function and KOOS Pain worsening ( P prior to TKA. KL worsening was strongly associated with future arthroplasty (Odds ratio = 5.0, 95% CI = 2.6–9.8) after adjustment for potential confounders. Conclusions Persons undergoing TKA 2 years later had substantial worsening pain and function over the 2-year pre-operative period as compared to a non-surgical sample matched based on KL grades. Almost 30% of persons who elect to undergo TKA undergo rapid disease progression and symptom worsening during the 2 years prior to TKA.

Summary Objective The American Academy of Orthopaedic Surgeons (AAOS) recently published appropriateness criteria for patients with knee osteoarthritis (OA) who are being considered for total knee arthroplasty (TKA). We evaluated the extent to which predictor variables used by the AAOS contribute to final classification, rated as "appropriate," "may be appropriate" or "rarely appropriate." Methods The RAND/UCLA Appropriateness method was used by AAOS to develop 864 clinical vignettes, each incorporating eight evidence-based variables associated with TKA outcome or need. Variables included function-limiting pain severity, knee OA severity, knee motion and age among others. The contribution of each variable to the overall classification was determined using multinomial regression. A classification tree method was applied to determine the combinations of variables that contributed to final classification for each vignette. Results Multinomial regression indicated that patient age, knee motion, OA severity and location were the four most powerful predictors of final classification. Function limiting pain, knee instability and lower limb alignment contributed little to the final classification. The classification tree had an accuracy of 86.7% and the most important contributors to classification were age, knee OA severity and pattern. Conclusion Function limiting pain, the most frequent reason endorsed by patients seeking TKA does not meaningfully contribute to the newly developed AAOS appropriateness criteria. The system is highly dependent on traditional variables that surgeons consider when evaluating patients for TKA: patient age, knee OA severity, knee OA pattern and knee motion.

Summary Objective Literature examining the effects of total hip arthroplasty (THA) on subsequent body weight gain is inconclusive. Determining the extent to which clinically relevant weight gain occurs following THA has important public health implications. Design We used multi-variable logistic regression to compare data from one of the largest US-based THA registries to a population-based control sample from the same geographic region. We also identified factors that increased risk of clinically important weight gain specifically among persons undergoing THA. The outcome measure of interest was weight gain of ≥5% of body weight up to 5 years following surgery. Results The multi-variable adjusted [age, sex, body mass index (BMI), education, comorbidity and pre-surgical weight change] odds ratio for important weight gain was 1.7 [95% confidence interval (CI), 1.06, 2.6] for a person with THA as compared to the control sample. Additional arthroplasty procedures during the 5-year follow-up further increased odds for important weight gain (OR = 2.0, 95% CI, 1.4, 2.7) relative to the control sample. A patient with THA had increased risk of important post-surgical weight gain of 12% (OR = 1.12, 95% CI, 1.08, 1.16) for every kilogram of pre-operative weight loss. Conclusions While findings should be interpreted with caution because of missing follow-up weight data, patients with THA appear to be at increased risk of clinically important weight gain following surgery as compared to peers. Patients less than 60 years and who have lost a substantial amount of weight prior to surgery appear to be at particularly high risk of important post-surgical weight gain.

Summary Objective To assess the influence of baseline score on concordance between the Minimal Clinically Important Difference (MCID) and Patient Acceptable Symptom State (PASS) estimates obtained on persons following total knee arthroplasty (TKA). Design Patients scheduled for TKA in 15 hospitals in Spain were recruited and provided pre-operative and 1-year postoperative Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain and Function scores. 1 year following surgery, patients completed questionnaires that determined the importance of any changes in status since surgery as well as the extent of satisfaction with the 1-year outcome. Kappa ( κ ) was used to determine the extent of concordance between MCID and PASS measures for the entire sample and after splitting the sample based on quartiles of the baseline WOMAC scores. Results A total of 923 patients participated in the study. The extent of concordance between MCID and PASS without regard to baseline score was κ = 0.41 (95% Confidence Interval (CI) = 0.36, 0.47) for WOMAC Function and after stratifying baseline scores into quartiles, κ = 0.72 (95%CI = 0.68, 0.77). Similar estimates were obtained for WOMAC Pain. Conclusions Baseline score has substantial influence on the extent of concordance between MCID and PASS for patients undergoing TKA. Clinicians should account for baseline score when interpreting either MCID or PASS and the extent to which these measures agree. These findings have potential to influence the interpretation of outcome following TKA.

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.

Summary Objective We determined whether baseline depressive symptoms, knee-related confidence and general psychological distress influenced changes in pain and function during 2 years of follow-up. Design We included persons in the Osteoarthritis Initiative (OAI) dataset with baseline pain of 1 or greater on a 0–10 scale in at least one knee and no knee or hip surgery during the 2-year follow-up (n=3407). The four outcome variables were repeated chair standing, 20m walk and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain and Disability. Linear mixed effects models assessed the association of each mental health variable with the yearly change in each baseline adjusted outcome measure after controlling for covariates. Results Depressive symptoms were significantly predictive of worsening in most outcomes. The magnitude of worsening predicted for each year was small. For example, the dichotomized WOMAC Pain model indicated that depressed persons experience more rapid worsening than non-depressed persons at an average rate of 0.59 WOMAC points per year (95% CI 0.176, 1.013, P =0.005). Similar significant but very small effects of depressive symptoms on other outcomes were observed. Knee confidence was not predictive of change. General psychological distress was predictive of change in 20-m walk and WOMAC Pain. Conclusions The most consistent psychological predictor of yearly worsening was baseline depressive symptoms. Although a statistically robust predictor of outcome, given that change was very small and highly dependent on baseline status, our results indicate that a considerable degree of persistent depressive symptoms would be required to have a meaningful effect on future self-reported outcome.

Background Knee arthroplasty traditionally is recommended for persons with substantial disability and disabling pain attributable to moderate or severe osteoarthritis (OA). Pain and functional status after arthroplasty may be influenced by the extent of knee OA before surgery and recent evidence suggests persons with less severe knee OA before undergoing TKA have greater pain levels and worse function than persons with more severe knee OA.