Effects of a Valgus Unloader Brace on Medial Femoral Cartilage Changes Following Walking Protocol

Participants will report to an initial screening session during which knee alignment will be determined using a long-lever goniometer. For the assessment of baseline knee alignment, the participant will stand with feet facing forward directly underneath corresponding acromion processes and weight evenly distributed. The first axis will be measured from ASIS to midpoint of the patella and the second axis will be measured from the midpoint of the patella to the tibial tuberosity. The valgus angle will be used to determine eligibility for the study. To be eligible for this study, participants must present with a valgus knee alignment angle of ≥180° on the dominant limb defined as the limb the participant would use to kick a ball. Weight and height measurements will also be measured and used to calculate BMI. Once eligible, participants will determine a self-selected walking speed by walking between 2 sets of infrared timing gates (TF100, TracTronix). Starting approximately 5 steps before the first timing gate, participants will be instructed to walk at a speed described as "comfortable walking over a sidewalk". Each participant will complete 3 trials and the average walking speed will be calculated.

Pre-loading Protocol

Participants will report to the laboratory at the same time of day (±2 hours) for both sessions to account for diurnal variations within the cartilage. Upon arrival, participants will sit on a treatment table in the long-sit position with knees fully extended for 45 mins to allow time for cartilage reformation.

Ultrasonographic Assessment of the Femoral Articular Cartilage While seated with their back up against the wall, participants will flex their knee to 140° measured using a manual goniometer while. A measuring tape will be secured to the length of the table so that the position of the posterior calcaneus can be recorded to allow for consistent positioning across trials 15. A LOGIQe US system (General Electric Co., Fairfield, CT) with a 12MHz linear probe will be used to image both the medial and lateral femoral cartilage. The probe will be placed transversely in line between the medial and lateral femoral condyles just superior to the patella and rotated to maximize reflection off the articular cartilage. A transparent grid will be placed over the US screen to improve reproducibility of the US image. The midpoint of the intercondylar groove will be aligned with the center of the grid.

The level of the cartilage-bone interface at the edge of the image on either side will be recorded in order to ensure consistent positioning across US assessments. Three images will be collected of each knee at each time point. Following each loading condition, the participant will be placed in the same position as the pre-loading US assessment using the tape measure. Three images of the femoral cartilage will be recorded from each knee. All post-walking images will be captured within 5 minutes of the loading protocol.