Wearable Sensors May Reliably Assess At-Home Activity in Patients With Knee Osteoarthritis

Wearable sensors are a reliable and feasible way to remotely assess gait and chair stand activity in patients with knee osteoarthritis (OA), according to study results published in Arthritis Care & Research. 

In light of the accelerated adoption of digital health technology during the COVID-19 pandemic, researchers examined the possibility of remotely assessing gait and chair stand movement in adults with knee OA, using inertial sensors in a home setting.

The study cohort included participants who were selected from a larger clinical study investigating an exercise intervention among individuals with knee OA. The participants were 50 years and older; had a BMI of 40 or lesser; had physician-diagnosed knee OA; a score of at least 3 of 12 on weight-bearing questions from the Knee Injury and OA Outcome Score Pain Subscale; and could walk for 20 minutes without assistance.

Researchers selected a “study leg” according to whichever knee was diagnosed by a physician with knee OA. If both legs were diagnosed, the leg with the highest pain score was selected.

Participants had 2 study visits: a lab visit and a remote visit, which took place at home. The order of visits was randomly assigned. Each participant was also provided with a wearable system, an armless chair, instructions for using the sensors and a tablet computer that could be used for video conferencing.

For the standardized walking task, participants walked at a comfortable pace for a total distance of 28 m. For the standardized chair stand task, the participants were asked to stand up 5 times, as quickly as possible, with arms crossed over the chest. After the first set of tests, participants removed the sensors, waited 15 minutes, applied the sensors again, and performed another trial of each task.

The researchers extracted spatiotemporal metrics of walking gait and chair stand duration from the sensor data and performed statistical analyses with intra-class correlation coefficients (ICC) and the Bland-Altman plot.

A total of 20 patients were included in the analysis. During the at-home visit, the test-retest reliability of walking speed (ICC=0.85) and chair stand duration (ICC=0.89) were good, and reliabilities of all other gait measures were excellent (ICC>0.9) when reported for the study leg. Similar reliability was noted for the contralateral leg, left leg, and right leg. Pearson’s correlation ranged from 0.81 to 0.97 for these tests.

Metrics for gait speed, stride length, cadence, and chair stand duration collected at home and in the lab had moderate agreement (0.5<ICC<0.75). Stride duration, step duration, stance, swing, double support, and terminal double support had good agreement (0.75<ICC<0.9).

One of the limitations of the study included the lack of generalizability, as 95% of participants self-identified as White. In addition, women were also disproportionately represented in the study, which was not reflective of knee OA statistics. When the at-home and lab assessments were compared, a small bias appeared, which the researchers attributed to participants walking more quickly in the lab than at home.

“Wearable sensors could be used to remotely monitor gait and chair stand function in participant’s natural environments at a lower cost, reduced participant and researcher burden, and greater ecological validity overcoming many limitations of lab visits,” the study authors noted. “Hence, our approach could be used in future longitudinal studies or clinical trials of people with knee OA,” they added.

Disclosure: This research was supported by Pfizer and Eli Lilly & Co. Please see the original reference for a full list of disclosures.