BIOMECHANICAL EFFECTS OF ASYMMETRIC CRANK ARM LENGTHS FOR ERGOMETER CYCLING IN PATIENTS WITH TOTAL KNEE ARTHROPLASTY

Total knee arthroplasty (TKA) is one of the most common treatments of end stage knee osteoarthritis. Not all individuals receiving these surgeries biomechanically recover to a desired level of physical function or improve subjective satisfaction during and after rehabilitation. Investigating accommodating alternatives to traditional rehabilitation exercises for individuals recovering from their TKA surgery is important for promoting improved outcomes, physically and mentally for these individuals. Cycling is often recommended for this population, but there is room to adapt cycling for the recovering knee specifically. This research investigates patients recovering from a TKA soon after their surgery while cycling with asymmetrically adjusted crank arms for the recovering limb through the use of traditional biomechanics and musculoskeletal simulation.

The first study, Chapter 4, evaluated the peak biomechanical responses of the lower limbs of patients 1-2 months post-TKA surgery when cycling on an ergometer using varying lengths of asymmetric and symmetric crank arms. The evidence from Chapter 4 suggests that asymmetric crank arms reduce knee range of motion while maintaining peak knee extension moments. These findings indicate that asymmetric crank arm usage is beneficial in accommodating difficulties with knee stiffness and range of motion early in recovery from TKA without introducing unwanted loading at the knee.

The second study, Chapter 5, calculated the differences between limbs of peak biomechanical variables between groups of participants who had unilateral or bilateral TKAs. Chapter 5 findings report almost no changes in the relationship between limbs of participants with unilateral of bilateral TKA. These findings suggest that the acute asymmetric crank arm intervention implemented will equivalently affect both groups and clinicians can prescribe this modality for unilateral and bilateral TKA.

The final study, Chapter 6, implemented musculoskeletal modeling simulations to investigate the effects of asymmetric crank arm usage in this population on the replaced limb’s estimated vertical knee contact forces as well as the peak muscle forces for musculature surrounding the knee. Chapter 6 results suggest that total vertical knee contact forces are lowered with decreased crank arm length. Future work should evaluate the longitudinal effects of this crank arm methodology to understand chronic adaptations that may occur in this population.