Knee Osteoarthritis Rehabilitation Through Rotational Inertia

Stair-stepping smoothness quantifies motor coordination during the step-up-and-over test by analyzing the fluidity and consistency of limb movements while ascending and descending stairs. It is calculated using a jerk-based smoothness metric adapted from Gonzales et al., where jerk is defined as the third derivative of the position trajectory with respect to time. The smoothness index is derived by numerically differentiating the position data x(t) obtained from motion capture three times to calculate jerk, then squaring and summing these jerk values over the duration of the movement. Lower values of the smoothness index indicate smoother, more coordinated movements. Differences in this metric will be compared between knee osteoarthritis patients and age-matched healthy controls, with variance explained through linear regression models, and between exercise intervention and delayed exercise subgroups to assess changes in motor control during stair negotiation. Unitless.

Bilateral differences in smoothness during stair-step negotiation (asymmetry between limbs). Unitless.

Muscle echogenicity is measured via diagnostic ultrasound, which quantifies the brightness intensity (greyscale pixel values) of muscle tissue images to provide a non-invasive assessment of muscle composition and quality. Unitless.

Muscle thickness is a non-invasive ultrasound measure obtained as the distance between superficial and deep muscle borders. Units: mm.

Muscle texture analysis using gray-level co-occurrence matrix (GLCM) is an advanced ultrasound imaging technique that quantitatively assesses the spatial distribution and relationship of pixel intensities within a muscle. Unitless.

Grip strength is objectively measured using a handheld dynamometer, recording the maximal isometric force over three trials. Units: kg.

Lower limb strength assessment are completed using the Biodex system involves isokinetic and isometric dynamometry to quantify maximal voluntary muscle force during knee extension and flexion. Units: Newton-meters.

The Timed Stair Ambulation test measures the time taken for an individual to ascend and descend a flight of stairs, reflecting lower limb muscle power, functional mobility, and endurance. The outcome is the recorded time in seconds to complete the stair climb task, with lower times indicating better physical performance and function. Units: seconds.

The Short Physical Performance Battery (SPPB) is an objective assessment tool for evaluating lower extremity physical function using three timed tests: standing balance, 4-meter usual-paced walk, and five repeated chair stands. Each component is scored from 0 to 4 points, yielding a total score range from 0 to 12, where higher scores indicate better physical performance and lower disability.

The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is a patient-reported questionnaire evaluating Osteoarthritis-related pain, stiffness, and physical function with subscale score ranges: Pain (0-20), Stiffness (0-8), and Physical Function (0-68). Higher scores indicate worse symptoms and greater disability. The total score sums all subscales, ranging from 0 to 96, with higher values representing more severe osteoarthritis impact.

Linear joint position measured using an optical tracking system during dynamic tasks. Unit of Measure: Meters (m)

Linear joint velocity derived from optical tracking data during dynamic tasks. Unit of Measure: Meters per second (m/s)

Linear joint acceleration derived from optical tracking data during dynamic tasks.

Unit of Measure: Meters per second squared (m/s²).

Angular velocity of the joint measured during dynamic tasks using optical tracking systems. Unit of Measure: Radians per second (rad/s)

Angular acceleration of the joint measured during dynamic tasks using optical tracking systems. Unit of Measure: Radians per second squared (rad/s²).

Active joint range of motion measured in the sagittal, frontal, and transverse planes during dynamic tasks using optical tracking systems. Unit of Measure: Degrees (°).

Net joint forces calculated using inverse dynamics during dynamic tasks. These measures reflect the mechanical loads experienced at the joint. Unit of Measure: Newtons (N).

Net joint moments calculated using inverse dynamics during dynamic tasks. These measures reflect the rotational loads acting about the joint and provide insight into muscle performance and load distribution. Unit of Measure: Newton-meters (N·m)

The Visual Analog Scale (VAS) is a unidimensional measure used to assess pain intensity. It consists of a 10-centimeter horizontal line with anchors at each end labeled "no pain" (0) and "worst pain imaginable" (10). Patients mark a point on the line corresponding to their pain level, which is measured in millimeters from the zero end. Higher scores indicate greater pain intensity. This scale provides a continuous range allowing sensitive detection of changes in pain over time.