Primary Total Knee Arthroplasty: How Does Residual Patellar Thickness Affect Patient-Oriented Outcomes?

BACKGROUND: Maintenance of the native patellar thickness has been deemed important for proper clinical outcomes after total knee arthroplasty (TKA). Our objective was to study the effects of the change in patellar thickness on patient-perceived outcomes (PPOs) after TKA. We hypothesized that reestablishing native patellar thickness after TKA results in better PPOs. METHODS: 819 consecutive patients undergoing primary TKA were studied. Patients were classified according to their postoperative patellar thickness into: (1) less than native patella thickness; (2) equal to native patella thickness; and (3) greater than native patella thickness. Difference in postoperative range of motion (ROM), PPOs and clinical scores, and delta-Δ-change were assessed. MANCOVA was used to assess for differences. RESULTS: No significant differences found based on postoperative patellar thickness (mean follow-up: 4.9 ± 2.1 years) for each ROM assessments. Those who reported more stiffness (Western Ontario and McMaster Universities Arthritis Index stiffness; P = .011) and lower knee active flexion (P = .046) preoperatively had "greater than native patella thickness" after surgery. Postoperatively, the "equal to native patella thickness" group reported significantly better quality of life (quality of well-being scale 7 total; P = .008) as well as better physical score (Short Form-36 role physical score; P = .03). The amount of improvement (delta-Δ-change), when restoring patellar thickness equal to the native demonstrated greatest improvements in quality of life (quality of well-being scale 7 total; P = .016) physical measures (Short Form-36 role physical [P = .025], and Western Ontario and McMaster Universities Arthritis Index stiffness scores [P = .006]). CONCLUSION: When compared with the native patellar thickness, a final postoperative difference (delta thickness) that ranges from -1.06 to 2.58 mm provides satisfactory results and does not seem to affect ROM after surgery.

Preoperative Glycemic Control on Total Joint Arthroplasty Patient-Perceived Outcomes and Hospital Costs.

BACKGROUND: The purpose of this study was to determine the influence of preoperative glycemic control in diabetic patients undergoing a primary total hip or knee arthroplasty. We wanted to study patient-perceived outcomes in the medium term, the length of stay, hospital costs, and rate of short-term postoperative complications. METHODS: One hundred twenty consecutive primary total joint arthroplasties (TJAs) performed in type 2 diabetic patients were stratified into 2 groups representing optimal and suboptimal preoperative glycemic control, based on serum levels of glycated hemoglobin (HbA1c), and those groups compared. RESULTS: The mean follow-up time was 5.9 years (range, 2.1-10.7 years). Both groups demonstrated improvement in all patient-perceived outcome measures after TJA, with no significant difference detected in any change of a measure between the groups. No significant difference was detected in the length of stay, hospital costs, or rate of short-term postoperative complications between the groups. CONCLUSION: Preoperative glycemic control in type 2 diabetic patients undergoing TJA did not affect patient-perceived outcomes in the medium term. Optimal vs suboptimal glycemic control in these patients also had no effect on the length of stay, hospital costs, or rate of short-term postoperative complications.

Prolonged Conservative Management in Total Joint Arthroplasty: Harming the Patient?

BACKGROUND: It is important to understand the long-term consequences of postponing total joint arthroplasty until the onset of severe functional impairment. Therefore, the purpose of this investigation was to determine and compare the midterm to long-term postoperative outcomes of patients who underwent total joint arthroplasty with severe vs less severe preoperative functional impairment. METHODS: A total of 105 primary unilateral total hip/knee arthroplasty patients were studied. Patients were divided into 2 groups-severely functionally impaired (preoperative Western Ontario and McMaster Osteoarthritis Index function ≥51 points) and functionally impaired (preoperative Western Ontario and McMaster Osteoarthritis Index function <51 points). RESULTS: At an average of 11.2 years postoperatively, the patients who were severely functionally impaired preoperatively had worse outcomes than did the patients with less severe preoperative functional impairment. CONCLUSION: Our data suggest that, after surgery, it is unlikely that patients who are severely functionally impaired preoperatively will ever catch up to patients who have the surgery with less severe functional impairment.

Total Joint Arthroplasty: A Granular Analysis of Outcomes in the Economically Disadvantaged Patient.

BACKGROUND: Poor patients experience more serious complications and worse outcomes after surgery than higher-income patients. Our objective was to study detailed patient sociodemographic characteristics and preoperative/postoperative patient-oriented outcomes in economically disadvantaged and non-economically disadvantaged primary total joint arthroplasty patients. METHODS: From a consecutive series, 213 economically disadvantaged patients and 1940 non-economically-disadvantaged patients were statistically analyzed. Baseline sociodemographic characteristics and pain visual analog scale, Quality of Well-Being Index 7, Short Form 36, and Western Ontario and McMaster Universities Arthritis Index scores recorded before and after surgery were compared between both groups controlling for baseline differences. Minimum follow-up was 1 year. RESULTS: Economically disadvantaged patients were significantly younger, more likely to be disabled, and had worse preoperative and postoperative scores. CONCLUSION: When compared with non-economically disadvantaged patients, economically disadvantaged patients consistently had lower function and worse quality of life before and after total joint arthroplasty.

Vitamin D insufficiency in patients with THA: prevalence and effects on outcome.

BACKGROUND: The consequences of vitamin D insufficiency in the elderly remain controversial. The prevalence and potential effects of its chronic insufficiency on quality of life and physical function in patients undergoing THA have received little attention. QUESTION/PURPOSES: We determined (1) prevalence of preoperative vitamin D insufficiency in patients undergoing THA and (2) relationships of insufficiency to patient-perceived outcomes (PPOs) and hip scores. METHODS: We retrospectively reviewed 62 consecutive patients who underwent 66 primary THAs. We excluded two patients with missing data and the second hip of bilateral THAs, leaving 60 patients (60 hips) for final inclusion. Based on preoperative plasma 25-hydroxyvitamin-D3 levels, patients were retrospectively assigned into a normal or insufficient group. We used two different thresholds (20 and 30 ng/mL) to define insufficiency; groups were set twice. We compared demographics, BMI, American Society of Anesthesiologists score, Charlson Comorbidity Index; albumin, transferrin, calcium levels; and total lymphocyte count between groups. The insufficient group had a higher mean BMI with the 20-ng/mL cutoff but not with the 30-ng/mL cutoff. We compared the 20-ng/mL cutoff groups (adjusting for BMI) and the 30-ng/mL cutoff groups in terms of preoperative and postoperative Quality of Well-being Scale, SF-36, WOMAC, Harris hip, and Merle d'Aubigné-Postel scores. Mean followup was 11 months (range, 3-24 months). RESULTS: The prevalence of vitamin D insufficiency was 30% (using 20 ng/mL) and 65% (using 30 ng/mL). Preoperative and postoperative Harris hip and Merle d'Aubigné-Postel scores were lower in patients with insufficiency using 30 ng/mL. No differences in PPOs or hip scores were found using 20 ng/mL. CONCLUSIONS: Hypovitaminosis D was common in patients with THA and associated with lower hip scores. Standardization of the definition of hypovitaminosis D is urgently needed so that further studies can properly evaluate its real prevalence, potential negative effects on function, and therapeutic effects of reversing insufficiency before THA.

Celecoxib and heterotopic bone formation after total hip arthroplasty.

We assessed the effectiveness of celecoxib in the prevention of heterotopic ossification (HO) following primary total hip replacement (THR). We studied 170 consecutive THRs. Sixty-three patients received celecoxib after surgery (200mg twice/daily) for 28 days and 84 did not. HO was more common in non-celecoxib patients than in the celecoxib-group at 3, 6, and 12 months (P =0.005, 0.004 and 0.01, respectively). At 1 year, fewer celecoxib recipients had Brooker classes II or III. None of the celecoxib patients developed HO Brooker class IV, while 2% in the non-celecoxib group did. No patient discontinued treatment or had revision for aseptic loosening. A short course of celecoxib for pain aids in the prevention of HO after primary THR, and could be a useful and safe option that does not interfere with anticoagulation.

Disparities in functional recovery after dysvascular lower limb amputation are associated with employment status and self-efficacy.

PURPOSE: Employment status is considered a determinant of health, yet returning to work is frequently a challenge after lower limb amputation. No studies have documented if working after lower limb amputation is associated with functional recovery. The study's purpose was to examine the influence of full-time employment on functioning after lower limb amputation. METHODS: Multisite, cross-sectional study of 49 people with dysvascular lower limb amputation. Outcomes of interest included performance-based measures, the Component Timed-Up-and-Go test, the 2-min walk test, and self-reported measures of prosthetic mobility and activity participation. RESULTS: Average participant age was 62.1 ± 9.7 years, 39% were female and 45% were persons of color. Results indicated that 80% of participants were not employed full-time. Accounting for age, people lacking full-time employment exhibited significantly poorer outcomes of mobility and activity participation. Per regression analyses, primary contributors to better prosthetic mobility were working full-time (R2 ranging from 0.06 to 0.24) and greater self-efficacy (R2 ranging from 0.32 to 0.75). CONCLUSIONS: This study offers novel evidence of associations between employment and performance-based mobility outcomes after dysvascular lower limb amputation. Further research is required to determine cause-effect directionalities. These results provide the foundation for future patient-centered research into how work affects outcomes after lower limb amputation. IMPLICATIONS FOR REHABILITATIONLower limb amputation can pose barriers to employment and activity participation, potentially affecting the quality of life.This study found that the majority of people living with lower limb amputation due to dysvascular causes were not employed full-time and were exhibiting poorer prosthetic outcomes.Healthcare practitioners should consider the modifiable variable of employment when evaluating factors that may affect prosthetic mobility.The modifiable variable of self-efficacy should be assessed by healthcare professionals when evaluating factors that may affect prosthetic mobility.

Do patient expectations about arthroplasty at initial presentation for hip or knee pain differ by sex and ethnicity?

BACKGROUND: Many studies show gender and ethnic differences in healthcare utilization and outcomes. Patients' presurgical cognitions regarding surgical outcomes also may vary by gender and ethnicity and play a role in explaining utilization and outcome differences. However, it is unclear whether and to what extent gender and ethnicity play a role in patients' presurgical cognitions. QUESTIONS/PURPOSES: Do gender and ethnicity influence outcome expectations? Is arthroplasty-related knowledge affected by gender and ethnicity? Do gender and ethnicity influence willingness to pay for surgery? METHODS: In a prospective, multicenter study we gave 765 patients an anonymous questionnaire on expectations, arthroplasty knowledge, and preferences before their consultation for hip and/or knee pain, from March 2005 to July 2007. RESULTS: Six hundred seventy-two of the 765 patients (88%) completed questionnaires. Non-Hispanics and men were more likely to indicate they would be able to engage in more activities. Non-Hispanics and men had greater arthroplasty knowledge. Hispanics and women were more likely to report they would not pay for a total joint arthroplasty (TJA) relative to non-Hispanics and men. CONCLUSIONS: Sex and ethnic differences in patients presenting for their initial visit to the orthopaedists for hip or knee pain influence expectations, knowledge, and preferences concerning TJAs. Longitudinal study of relationships between patients' perceptions and utilization or outcomes regarding TJA is warranted.

Mental health and outcomes in primary total joint arthroplasty.

A consecutive series of 640 total joint arthroplasty patients was interviewed before surgery and at a minimum of 2 years following surgery. Statistical analyses were conducted to examine the effect of psychological distress and other patient characteristics on outcomes (Western Ontario and McMaster Universities Osteoarthritis Index, Short Form 36, and Quality of Well-Being index). Before and after surgery, distressed subjects had significantly lower scores than nondistressed subjects for most dependent measures (P range, .05 ≤ .001). All mean outcomes improved by follow-up in both groups (P ≤ .001) except mental health scores of nondistressed subjects. Stepwise regression analysis found that low baseline mental health score, non-Hispanic ethnicity, and fewer years since procedure were the strongest predictors of worse Western Ontario and McMaster Universities Osteoarthritis Index scores at follow-up. Although the magnitude of improvement is similar to nondistressed subjects, distressed patients do not achieve comparable functional and psychosocial outcomes.

Ethnic and racial factors influencing well-being, perceived pain, and physical function after primary total joint arthroplasty.

BACKGROUND: Studies suggest, even when controlling for disease severity, socioeconomic status, education, and access to care, racial and ethnic minorities receive lower-quality health care and have worse perceived pain and function before and after total joint arthroplasty. QUESTION/PURPOSES: We evaluated the influence of race and ethnicity on well-being, pain, and function after total joint arthroplasty and determined whether race, ethnicity, sex, and joint involvement influenced perceived function and pain after total joint arthroplasty. PATIENTS AND METHODS: We retrospectively reviewed the records of 1749 patients receiving total joint arthroplasty (739 hips and 1010 knees). Sixty-eight percent were women, with a mean age of 65 years at followup. We assessed patients preoperatively and at a minimum of 2 years (mean, 5.1 years; range, 2-16 years) on perceived well-being, function, and pain, as well as clinical assessment tools. Also, we assessed the behavior of dependent measures between groups over time. RESULTS: Preoperatively, in both TKA and THA candidates, African American patients presented with worse scores. Postoperatively, all patients had substantial improvement, yet African Americans who had TKA or THA continued to have worse scores on some measures. In both TKA and THA, women had worse scores. CONCLUSIONS: Racial and ethnic minorities undergoing hip and knee arthroplasty appear to have worse patient-perceived outcomes (well-being, pain, and function) when compared to whites. This discrepancy is most pronounced for African Americans. LEVEL OF EVIDENCE: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Patient perceived outcomes after primary hip arthroplasty: does gender matter?

BACKGROUND: Total hip arthroplasty (THA) provides high functional scores and long-term survivorship. However, differences in function and disability between men and women before and after arthroplasty are not well understood. QUESTIONS/PURPOSES: We determined if there was a gender difference in patient-perceived functional measures and range of motion in primary THA. METHODS: We retrospectively studied 532 patients (658 hips) undergoing primary THA. A total of 59% were women and 41% were men. Patients were assessed preoperatively and at minimum 2 years using Quality of Well-being, SF-36, WOMAC, and Harris hip score. We determined if differences existed between genders before and at followup for all dependent measures. Independent t-tests were also used to determine differences between genders concerning the change (Δ) scores and hip range of motion. The time course of perceived functional recovery was also documented. RESULTS: Males were on average 5 years (58) younger than females (63). Before surgery, females scored worse than males on the Harris hip score, WOMAC function, WOMAC pain, and WOMAC total scores. All scores improved at followup in both groups. Regardless of time, females had lower scores than males. However, females had greater improvement over males for WOMAC function (39 versus 35), WOMAC pain (11 versus 10), and WOMAC total (53 versus 48). CONCLUSIONS: Substantial gender functional differences exist before treatment. However, women reported greater improvement as a result of the intervention when compared with men. LEVEL OF EVIDENCE: Level III, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Fear in arthroplasty surgery: the role of race.

UNLABELLED: Understanding the difference in perceived functional outcomes between whites and blacks and the influence of anxiety and pain on functional outcomes after joint arthroplasty may help surgeons develop ways to eliminate the racial and ethnic disparities in outcome. We determined the difference in functional outcomes between whites and blacks and assessed the influence of fear and anxiety in total joint arthroplasty outcomes in 331 patients undergoing primary hip and knee arthroplasty. WOMAC, Quality of Well Being, SF-36, and Pain and Anxiety Symptoms Scale (PASS) were administered pre- and postoperatively (average 5-year followup). For the SF-36 General Health Score, blacks reported having worse perceived general health than whites before surgery. Regardless of time, blacks scored worse than whites for all measures except for the SF-36 physical function and general health scores. Blacks had a greater fear score (ie, that associated with the procedure) and total PASS score. For both races, there was a low association between the fear dimensions and dependent measures before and after surgery. Black patients undergoing hip and knee arthroplasty had lower scores than whites in most outcome measures regardless of time of assessment. We found higher fear levels before joint arthroplasty in blacks compared with whites. After surgery, blacks had much higher associations of the fear subscale, cognitive subscale, and total PASS score with the WOMAC physical function, pain, and total scores. LEVEL OF EVIDENCE: Level II, prospective controlled cohort study. See Guidelines for Authors for a complete description of levels of evidence.

The effects of the contract-relax-antagonist-contract form of proprioceptive neuromuscular facilitation stretching on postural stability.

To investigate the effects of the contract-relax-antagonist-contract (CRAC) form of proprioceptive neuromuscular facilitation (PNF) stretching, with and without a warm-up, on postural stability. Thirty volunteers (15 men and 15 women, age: 25.17 +/- 5.4 years, height: 173.76 +/- 8.2 cm, and weight: 72.03 +/- 14.87 kg) were randomly assigned to 1 of 3 conditions: warm-up and stretch (WS), stretching only (SO), and a control condition (CON). Contract-relax-antagonist-contract PNF of the hamstrings, plantar flexors, and hip flexors was performed during WS and SO. A 6-minute treadmill warm-up was applied before CRAC in the WS condition. Measures of anterior/posterior and medial/lateral (M/L) postural stability were taken before and after treatment conditions. A 2 x 3 analysis of variance was used to assess for differences between conditions. Significance was set at p < 0.05. There was a time x condition interaction (F = 3.962,58; p = 0.024, Power = 0.69) for M/L stability. There was a difference between WS and CON (p = 0.037, Power = 0.57) and SO and CON (p = 0.041, Power = 0.51) posttesting. This study suggests that CRAC PNF stretching with or without warm-up improves M/L stability. Contract-relax-antagonist-contract form of stretching is a useful protocol for improving M/L stability.

Is postoperative function after hip or knee arthroplasty influenced by preoperative functional levels?

Our objective was to evaluate functional outcomes after surgery in a subgroup of patients presenting for hip and knee surgery who had low functional scores before surgery. One hundred twenty-seven unilateral total hip and knee arthroplasty patients were assessed preoperatively and 3 consecutive years after arthroplasty using: Western Ontario and McMaster University Osteoarthritis Index (WOMAC), Short Form 36 (SF-36), and the Quality of Well-Being index scales. Patients were placed into 2 groups based on preoperative WOMAC function scores; 51 points or more, worse functioning group, and less than 51 points, higher functioning group. Regardless of time, the worse functioning group in both procedures performed worse on the Quality of Well-Being index, SF-36 (function score), SF-36 (social score), and WOMAC total and pain scores (P < or = .0001). The greatest change (range, 2%-638%) for all variables in both groups for both procedures occurred during the first year. Patients that had severe/extreme functional impairment had worse 3-year outcomes compared with patients getting surgery when their functional levels were better.

All-Patient Refined Diagnosis-Related Groups in primary arthroplasty.

Our objective was to determine if the All-Patient Refined Diagnosis-Related Groups (APR-DRGs) and other comorbidity scores correlate with pain level, functional abilities, and hospital cost after primary total joint arthroplasty (TJA). Three hundred three patients having TJA were evaluated with average follow-up of 21 months. Western Ontario and McMaster Universities osteoarthritis index, Short-Form 36, and Quality of Well-Being index were administered before and after surgery. The APR-DRG subclassification including severity of illness (SOI) subclass scores and risk of mortality (ROM), Charlson index, American Society of Anesthesiologist (ASA), Charnley score, length of stay, and hospital costs were reported. Patients in a higher SOI and ROM subclasses had a statistically significant decrease in functional outcomes scores, longer length of stay, and greater hospitals costs than those in lower subclasses. However, correlations of comorbidity categories with outcome scores were poor. The APR-DRG classification helps identify those individuals with worse function and is specially suited in identifying those patients who incur a higher hospital cost.

Multimodal pain management and arthrofibrosis.

Pain control after arthroplasty has been a key concern for orthopedic surgeons. After total knee arthroplasty (TKA), a small group of patients developed a painful joint with suboptimal range of motion. Manipulation under anesthesia increases flexion and extension while decreasing pain in most cases. The objective of the present investigation is to asses the effect of a multimodal pain management protocol on arthrofibrosis in primary TKAs. A cohort of 1136 patients who underwent primary TKA was selected. Patients were divided into 2 groups: group A had 778 procedures performed using a traditional approach to pain control; group B included 358 procedures that received multimodal pain management. Group A had an incidence of manipulation of 4.75% (37/778). Of 357 patients, 8 required manipulation in group B, which is an incidence of 2.24%. We recommend that orthopedic surgeons consider using a multimodal pain management protocol for TKA.

Accuracy of knee range of motion assessment after total knee arthroplasty.

Measurement of knee joint range of motion (ROM) is important to assess after total knee arthroplasty. Our objective was to determine level of agreement and accuracy between observers with different knowledge on total ROM after total knee arthroplasty. Forty-one patients underwent x-ray of active and passive knee ROM (gold standard). Five different raters evaluated observed and measured ROM: orthopedic surgeon, clinical fellow, physician assistant, research fellow, and a physical therapist. A 1-way analysis of variance was used to determine differences in ROM between raters over both conditions. Limit of agreement for each rater for both active and passive total ROM under both conditions was calculated. Analysis of variance indicated a difference between raters for all conditions (range, P = .004 to P < or =.0001). The trend for all raters was to overestimate ROM at higher ranges. Assessment of ROM through direct observation without a goniometer provides inaccurate findings.

Rehabilitation Outcomes for Total Knee Arthroplasties: Continuous Adductor Canal Block Versus Continuous Femoral Nerve Block.

OBJECTIVE: To determine whether any strength, range of motion (ROM), or functional improvement exists in the adductor canal block (ACB) group after completion of inpatient rehabilitation and following the removal of the continuous block. DESIGN: Retrospective cohort. SETTING: Inpatient rehabilitation at discharge and outpatient orthopedic clinic for follow-up. PARTICIPANTS: Two hundred forty-six consecutive primary total knee arthroplasties (TKAs; N = 221 patients) performed by a single surgeon in a single institution between July 2013 and August 2015 for a diagnosis of osteoarthritis. INTERVENTIONS: All TKA cases received a continuous femoral nerve block (FNB) from July 2013 to August 2014 for postoperative pain control. From August 2014 through August 2015, all TKAs received a continuous ACB. MAIN OUTCOME MEASURES: Manual muscle tests (MMTs; 0-5 scale) of the quadriceps and passive ROM of the knee were assessed at 3 time periods (hospital discharge [HD], 1-2 weeks, and 1 month). Patient-oriented outcomes and clinical knee scores were examined preoperatively and postoperatively at 3 and 6 months. RESULTS: 63.6% of FNB cases had an MMT less than 3 at HD and 36.4% of FNB cases had an MMT of 3 or greater at HD. Conversely, 46% of ACB cases had an MMT less than 3 at HD and 54% had an MMT of 3 or greater at HD. There were no statistically significant differences in all postoperative variables at all tested time periods. CONCLUSIONS: This study showed no short-term postoperative advantages in the ACB group after catheter removal. The superior inpatient rehabilitation course in the continuous ACB group is likely not long enough to translate into any maintained benefit following catheter removal. Nevertheless, the trend toward greater strength in the ACB group in the immediate short term at HD warrants further investigation.

Relationship of closed and open chain measures of strength with perceived physical function and mobility following unilateral total knee replacement.

BACKGROUND AND PURPOSE: The association between closed-chain knee extensor strength and perceived physical function following primary knee replacement has not received much attention.The purpose of this investigation was to determine the relationship of closed and open chain measures of strength with self-reported measures of physical function and mobility following unilateral knee replacement. METHODS: Subjects were 9 individuals (68. 7 +/- 2.3 years) approximately 16 months postsurgery. The independent variables were closed-chain (elastic) and open-chain (isometric) measures of strength, while the dependent measures were perceived physical function (WOMAC) and mobility (Timed Up and Go, TUG). The relationship between independent and dependent variables was described using Spearman Rho correlation coefficients. RESULTS: Force produced during the closed-chain assessment was strongly associated to the WOMAC physical function dimension (-.96) and total WOMAC score (-.87). A poor to low relationship existed between the open-chain measure of strength and the physical function dimension (-.34) and the total WOMAC score (-.17). Force production of the entire lower limb, measured in the closed-chain was moderately related (-.62) with the TUG. The association between knee extensor isometric torque and the TUG (-.25) was low. CONCLUSIONS: Closed-chain assessment of entire lower limb strength, rather than open-chain measures of knee extensor strength, may provide greater insight to functional limitations.

Use of a squatting movement as a clinical marker of function after total knee arthroplasty.

OBJECTIVE: The aims of this study were to evaluate weight bearing during standing and 30- and 60-degree squats approximately 1 wk and 2 mos after surgery and determine whether weight bearing during squatting could be a better clinical marker than standing for identifying perceived functional limitation approximately 1 wk after surgery. A further objective was to determine whether age, body mass index, and number of outpatient visits over the course of rehabilitation predicted weight bearing during a squat approximately 2 mos after surgery. DESIGN: The percentage of body weight placed over both limbs during stand and 30- and 60-degree squats in 38 patients (25 women and 13 men) who had primary unilateral knee arthroplasty was determined. An asymmetry index would be used as a marker that could discriminate between those who perceived at least moderate difficulty with functional tasks and those who perceived only slight or no difficulty with functional activities based on the physical function dimension of the Western Ontario McMaster Universities Osteoarthritis index approximately 1 wk after surgery. Stepwise regression was conducted to determine whether clinical characteristics predicted weight-bearing asymmetry at discharge. RESULTS: At initial visit (first observation), and compared with the uninvolved side, individuals placed significantly less body weight over the involved or operated limb for stand and 30- and 60-degree squats (P < 0.0001). Results were similar at last rehabilitation visit (second observation). Identifying at least moderate self-reported difficulty with functional tasks based on the receiver operator characteristic curve for the asymmetry index for the stand position was 0.64, whereas for the 30- and 60-degree squats, the area under the curve was 0.81 and 0.89, respectively. At discharge from rehabilitation, there was a moderate to good direct relationship (r = 0.70) between the number of rehabilitation visits completed and the weight-bearing asymmetry index for the 60-degree squat. CONCLUSIONS: On the first outpatient visit, individuals who had primary unilateral knee arthroplasty placed more body weight over the uninvolved side for the three weight-bearing positions. With high probability, the asymmetry index for both squatting angles identified perceived functional difficulty. As rehabilitation visits increased, there was a direct association to improved interlimb weight-bearing symmetry when squatting to 60 degrees.