The purpose of this study is to determine the sensitivity of a wearable sensor to detect changes in knee joint loading using an experimental knee joint effusion as a model for a common clinical physiological alteration in joint status. The rationale for this project is that it will establish the efficacy of an inexpensive, clinically, and publicly available device that can detect changes in biomechanical loading due to acute physiologic change in joint status. The study will utilize a cross-sectional cohort study design and will seek to enroll 25 male and female healthy adult participants (18-35 yo). Participants will report to the laboratory for three total sessions (Session 1: informed consent and task familiarization; Session 2: testing; Session 3: knee joint status assessment). The primary outcomes of interest include lower extremity thigh and shank acceleration and velocity data (wearable sensor data), lower extermity 3D kinematics and kinetics (motion capture data), and lower extremity muscle function (EMG data) during walking gait, as well as functional balance and patient-reported subjective outcomes. Data will be analyzed by calculating change scores from the pre- to post-experimental effusion outcome measure testing. Paired-samples t-tests and Cohen's d effect sizes will be used to assess changed in wearable sensor data from pre- to post-experimental effusion. Correlation statistics will be used to determine if there are association between the motion capture and wearable sensor data. The potential risks associated with an experimental joint effusion will be addressed by maintaining appropriate sterile conditions and having the participant check-in with the PI (licensed healthcare provider) at 48 hours following testing session.

Inclusion Criteria:

• Male and female
• Chronological age 18-35 at the time of study participation
• Physically active (at least 30 minutes of physical activity, 3x/week)
• Tegner Activity Scale score at least 5/10

Exclusion Criteria:

• History of lower extremity or lumbar spine surgery.
• History of lower extremity or lumbar spine injury in the prior 6 months.
• History of major ligamentous damage.
• Current knee pain.
• Known neurological condition, autoimmune condition, cardiovascular disease.
• History of epilepsy, seizures, concussion within the prior 6 months.
• Currently taking pain altering medication.
• Fear of needles
• Unable to read and understand English language
• Pregnancy