Daily Walking and the Risk of Knee Replacement Over 5 Years Among Adults With Advanced Knee Osteoarthritis in the United States.

OBJECTIVE: To examine the association of the volume and intensity of daily walking at baseline with the risk of knee replacement (KR) over 5 years in adults with advanced structural knee osteoarthritis. DESIGN: Prospective, longitudinal, and multicenter observational study. SETTING: Osteoarthritis Initiative study with follow-up from 2008-2015. PARTICIPANTS: Community-dwelling adults with or at risk of knee osteoarthritis were recruited from 4 sites in the United States (N=516; mean age, 67.7±8.6y; body mass index, 29.3±4.7 kg/m2; 52% female). We included participants with advanced structural disease, without KR and had valid daily walking data (quantified using Actigraph GT1M), at baseline. INTERVENTIONS: Not applicable. MAIN OUTCOMES: KR. Walking volume was measured as steps/day and intensity as minutes/day spent not walking (0 steps/min) and walking at very light (1-49 steps/min), light (50-100 steps/min), or moderate (>100 steps/min) intensities. To examine the relationship of walking volume and intensity with the risk of KR, we calculated hazard ratios (HRs) and 95% confidence intervals (CIs) adjusting for covariates. RESULTS: Of 516 adults with advanced structural disease, 88 received a KR over 5 years (17%). Walking an additional 1000 steps/d was not associated with the risk of KR (adjusted HR=0.95; 95% CI, 0.84-1.04). Statistically, replacing 10 min/d of very light and light walking with 10 min/d of moderate walking reduced the risk of KR incidence by 35% and 37%, respectively (adjusted HR=0.65, 95% CI, 0.45-0.94, for very light and adjusted HR=0.63; 95% CI, 0.40-1.00, for light). CONCLUSIONS: Daily walking volume and intensity did not increase KR risk over 5 years and may be protective in some cases in adults with advanced structural knee osteoarthritis.

Joint Association of Moderate-to-vigorous Intensity Physical Activity and Sedentary Behavior With Incident Functional Limitation: Data From the Osteoarthritis Initiative.

OBJECTIVE: To examine the joint association of moderate-to-vigorous intensity physical activity (MVPA) and sedentary behavior with the risk of developing functional limitation 4 years later in adults with knee osteoarthritis (OA). METHODS: Using 48-month (baseline) accelerometry data from the Osteoarthritis Initiative, we classified participants as Active-Low Sedentary (≥ 1 10-min bout/week of MVPA, lowest tertile for standardized sedentary time), Active-High Sedentary (≥ 1 10-min bout/week of MVPA, top 2 tertiles for standardized sedentary time), Inactive-Low Sedentary (zero 10-min bouts/week of MVPA, lowest tertile for standardized sedentary time), and Inactive-High Sedentary (zero 10-minute bouts/week of MVPA, top 2 tertiles for standardized sedentary time) groups. Functional limitation was defined as > 12 seconds for the 5-repetition sit-to-stand test (5XSST) and < 1.22 m/s gait speed during the 20-meter walk test. To investigate the association of exposure groups with risk of developing functional limitation 4 years later, we calculated adjusted risk ratios (aRR; adjusted for potential confounders). RESULTS: Of 1091 and 1133 participants without baseline functional limitation, based on the 5XSST and 20-meter walk test, respectively, 15% and 21% developed functional limitation 4 years later. The Inactive-Low Sedentary and Inactive-High Sedentary groups had increased risk of developing functional limitations compared to the Active-Low Sedentary and Active-High Sedentary groups. The Inactive-Low Sedentary group had 72% (aRR 1.72, 95% CI 1.00-2.94) and 52% (aRR 1.52, 95% CI 1.03-2.25) more risk of developing functional limitation based on the 5XSST and 20-meter walk test, respectively, compared to the Active-Low Sedentary group. CONCLUSION: Regardless of sedentary category, being inactive (zero 10-min bouts/week in MVPA) may increase the risk of developing functional limitation in adults with knee OA.

Does the 1-year Decline in Walking Speed Predict Mortality Risk Beyond Current Walking Speed in Adults With Knee Osteoarthritis?

OBJECTIVE: To investigate whether walking speed at 1 timepoint, decline over the past 12 months, or both predict mortality risk over 11 years in adults with, or at risk of, knee osteoarthritis (OA). METHODS: Using the data from the Osteoarthritis Initiative, we defined slow versus adequate walking speed as walking < 1.22 versus ≥ 1.22 m/s on a 20m walk test during the 12-month follow-up visit. We defined meaningful decline (yes/no) as slowing ≥ 0.08 m/s over the past year. At the 12-month visit, we classified adequate sustainers as those with adequate walking speed and no meaningful decline, slow sustainers as slow walking speed and no meaningful decline, adequate decliners as adequate walking speed and meaningful decline, and slow decliners as slow walking speed and meaningful decline. Mortality was recorded over 11 years. To examine the association of walking speed with mortality, HR and 95% CI were calculated using Cox regression, adjusted for potential confounders. RESULTS: Of 4229 participants in the analytic sample (58% female, age 62 ± 9 yrs, BMI 29 ± 5 kg/m2), 6% (n = 270) died over 11 years. Slow sustainers and slow decliners had 2-times increased mortality risk compared to adequate sustainers (HR 1.96, 95% CI 1.44-2.66 for slow sustainers, and HR 2.08, 95% CI 1.46-2.96 for slow decliners). Adequate decliners had 0.43 times the mortality risk compared with adequate sustainers (HR 0.57, 95% CI 0.32-1.01). CONCLUSION: In adults with, or at risk of, knee OA, walking slower than 1.22 m/s in the present increased mortality risk, regardless of decline over the previous year.

"I've been to physical therapy before, but not for the knees." A qualitative study exploring barriers and facilitators to physical therapy utilization for knee osteoarthritis.

BACKGROUND: Physical therapy (PT) is recommended to reduce pain and improve function. However, only 10%-15% of adults with knee osteoarthritis (OA) use PT in the United States. The purpose of this study was to explore patient-reported barriers and facilitators to PT utilization for knee OA, to understand why PT is underutilized. METHODS: Qualitative descriptive study using semi-structured interviews was conducted, that is, one-on-one phone interviews with adults from local community centers. Participants were eligible if they were fluent in English and self-reported knee OA (1) over 45 years of age, (2) have activity-related knee pain, and (3) have no morning stiffness or morning stiffness in the knee(s) for ≤30 min. Interviews were audio-recorded and transcribed. To identify barriers and facilitators to PT utilization for knee OA, a coding framework, thematic analysis, and a constant comparative approach were used. RESULTS: Of 22 participants with health insurance and who participated, 59% were considering PT, 23% refused PT, and 18% used PT for knee OA. Themes identified as either barriers or facilitators for participants were (1) previous experience with PT, (2) physician referral, (3) beliefs about treatment efficacy before and after knee replacement surgery, (4) insurance coverage, and (5) preference to avoid surgery. CONCLUSION: A previous positive encounter with PT and a physician referral may facilitate PT utilization for adults with knee OA. Knowledge about and access to PT services were not identified as barriers related to PT utilization. Further research is necessary to confirm findings in a broader group of adults with knee OA.

The Association of an Increasing Waist Circumference and Risk of Incident Low Physical Function in Adults with Knee Osteoarthritis.

OBJECTIVE: To investigate an 8-year change in waist circumference (WC) with the risk of incident low physical function over 1 year in adults with, or at risk of, knee osteoarthritis (OA). METHODS: Data from the Osteoarthritis Initiative were used. Change in WC was measured from study enrollment (0 month) to the 96-month visit and classified as Increase (≥ 5cm gain) or Maintain (< 5cm gain). We identified World Health Organization (WHO) risk category based on WC at study enrollment as Large WC (males ≥ 102 cm, females ≥ 88 cm) or Small WC (males < 102 cm, females < 88 cm). The outcome was incident low physical function (≥ 28 Western Ontario and McMaster Universities Osteoarthritis Index physical function subscale) at the 108-month visit. To investigate the association of the 8-year change in WC with the risk of low physical function, we calculated risk ratios (95% CI) and adjusted for potential confounders. We repeated the analyses stratified by the WHO disease risk category. RESULTS: The Increase WC group had 1.43 (95% CI 1.04-1.96) times the risk of incident low physical function compared to adults in the Maintain WC group. Adults with a Large WC at baseline who increased WC had 1.55 (95% CI 1.00-2.37) times the risk of incident low physical function compared to those who maintained WC. Adults with a Small WC at baseline who increased WC had 1.97 (95% CI 0.84-4.63) times the risk compared to those who maintained WC. CONCLUSION: Increasing WC increases the risk of incident low physical function in the following year. Maintaining WC may mitigate developing low physical function.

Feasibility and Preliminary Outcomes of a Physical Therapist-Administered Physical Activity Intervention After Total Knee Replacement.

OBJECTIVE: To explore the feasibility, fidelity, safety, and preliminary outcomes of a physical therapist-administered physical activity (PA) intervention after total knee replacement (TKR). METHODS: People who had undergone a unilateral TKR and were receiving outpatient physical therapy (PT) were randomized to a control or intervention group. Both groups received standard PT for TKR. The intervention included being provided with a Fitbit Zip, step goals, and 1 phone call a month for 6 months after discharge from PT. Feasibility was measured by rates of recruitment and retention, safety was measured by the frequency of adverse events, and fidelity was measured by adherence to the weekly steps/day goal created by the physical therapist and participant monitoring of steps/day. An Actigraph GT3X measured PA, which was quantified as steps/day and minutes/week of engaging in moderate-to-vigorous PA. Our preliminary outcome was the difference in PA 6 months after discharge from PT between the control and intervention groups. RESULTS: Of the 43 individuals who were enrolled, 53.4% were women, the mean ± SD age was 67.0 ± 7.0 years, and the mean ± SD body mass index was 31.5 ± 5.9 kg/m2 . For both the control and intervention groups, the recruitment and retention rates were 64% and 83.7%, respectively, and adherence to the intervention ranged from 45% to 60%. No study-related adverse events occurred. The patients in the intervention group accumulated a mean 1,798 more steps/day (95% confidence interval [95% CI] 240, 3,355) and spent 73.4 more minutes/week (95% CI -14.1, 160.9) engaging in moderate-to-vigorous PA at 6 months than those in the control group. CONCLUSION: A physical therapist-administered PA intervention is feasible and safe, demonstrates treatment fidelity, and may increase PA after TKR. Future research is needed to establish the effectiveness of the intervention.

A Physical Therapist-Administered Physical Activity Intervention After Total Knee Replacement: Protocol for a Randomized Controlled Trial.

Background: The definitive treatment for knee osteoarthritis is a total knee replacement, which results in a clinically meaningful improvement in pain and physical function. However, evidence suggests that physical activity (PA) remains unchanged after total knee replacement (TKR). Objective: The objective of this study is to investigate the efficacy, fidelity, and safety of a physical therapist-administered PA intervention for people after TKR. Design: This study will be a randomized controlled trial. Setting: The setting is an outpatient physical therapy clinic. Participants: The participants are 125 individuals who are over the age of 45 and are seeking outpatient physical therapy following a unilateral TKR. Intervention: In addition to standardized physical therapy after TKR, the intervention group will receive, during physical therapy, a weekly PA intervention that includes a wearable activity tracking device, individualized step goals, and face-to-face feedback provided by a physical therapist. Control: The control group will receive standardized physical therapy alone after TKR. Measurements: The efficacy of the intervention will be measured as minutes per week spent in moderate to vigorous PA at enrollment, at discharge, and at 6 months and 12 months after discharge from physical therapy. The fidelity and safety of the intervention will be assessed throughout the study. Limitations: Participants will not be masked, PA data will be collected after randomization, and the trial will be conducted at a single site. Conclusions: The goal of this randomized controlled trial is to increase PA after TKR. A protocol for investigating the efficacy, fidelity, and safety of a physical therapist-administered PA intervention for people after TKR is presented. The findings will be used to support a large multisite clinical trial to test the effectiveness, implementation, and cost of this intervention.

Are Older Adults With Symptomatic Knee Osteoarthritis Less Active Than the General Population? Analysis From the Osteoarthritis Initiative and the National Health and Nutrition Examination Survey.

OBJECTIVE: To compare objectively measured physical activity in older adults with symptomatic knee osteoarthritis (OA) with similarly aged adults without osteoarthritis (OA) or knee symptoms from the general population. METHODS: We included people ages 50-85 years with symptomatic knee OA from the Osteoarthritis Initiative (OAI, n = 491), and ages 50-85 years from the general population using National Health and Nutrition Examination Survey (NHANES, n = 449) data. A uniaxial accelerometer was worn for ≥10 hours/day for ≥4 days in the NHANES group in 2003-2004 and in the OAI group in 2008-2010. We calculated time spent in moderate-to-vigorous physical activity (MVPA in minutes/day) and described differences in MVPA and demographic variables between the samples. We conducted matched-pairs sensitivity analyses to further evaluate the role of potential confounders. RESULTS: Both cohorts had similarly low levels of physical activity in age- and sex-specific strata. Time in MVPA ranged from a median of 1-22 minutes/day in people with symptomatic knee OA, and from 1-24 minutes/day in the general population without OA or knee pain. These results were similar in sensitivity analyses. CONCLUSION: Time spent in MVPA was similarly low in those with symptomatic knee OA as in older adults without knee pain or OA.

Minimum Performance on Clinical Tests of Physical Function to Predict Walking 6,000 Steps/Day in Knee Osteoarthritis: An Observational Study.

OBJECTIVE: Evidence of physical function difficulties, such as difficulty rising from a chair, may limit daily walking for people with knee osteoarthritis (OA). The purpose of this study was to identify minimum performance thresholds on clinical tests of physical function predictive to walking ≥6,000 steps/day. This benchmark is known to discriminate people with knee OA who develop functional limitation over time from those who do not. METHODS: Using data from the Osteoarthritis Initiative, we quantified daily walking as average steps/day from an accelerometer (Actigraph GT1M) worn for ≥10 hours/day over 1 week. Physical function was quantified using 3 performance-based clinical tests: 5 times sit-to-stand test, walking speed (tested over 20 meters), and 400-meter walk test. To identify minimum performance thresholds for daily walking, we calculated physical function values corresponding to high specificity (80-95%) to predict walking ≥6,000 steps/day. RESULTS: Among 1,925 participants (mean ± SD age 65.1 ± 9.1 years, mean ± SD body mass index 28.4 ± 4.8 kg/m2 , and 55% female) with valid accelerometer data, 54.9% walked ≥6,000 steps/day. High specificity thresholds of physical function for walking ≥6,000 steps/day ranged 11.4-14.0 seconds on the 5 times sit-to-stand test, 1.13-1.26 meters/second for walking speed, or 315-349 seconds on the 400-meter walk test. CONCLUSION: Not meeting these minimum performance thresholds on clinical tests of physical function may indicate inadequate physical ability to walk ≥6,000 steps/day for people with knee OA. Rehabilitation may be indicated to address underlying impairments limiting physical function.