The purpose of this investigation is to determine both patient-reported and performance-based outcomes, specifically muscle function and kinematic/kinetic outcomes, between four different surgical total knee prostheses in individuals following TKA. Change scores will be determined based on patient-reported outcomes, kinematic/kinetic data, knee extension strength/power, static/dynamic balance control, mobility measures and functional performance testing during functional tasks (i.e. walking, ascending/descending stairs, sit-to-stand). After evaluating the pattern of change in lower-extremity function, the investigators will be better prepared to address residual functional impairments and prognostic factors linked to maximal recovery over two years.

Inclusion Criteria:

• adults > 40 years of age that are scheduled for primary TKA
• if they have had a previous TKA, it needs to have been performed on the opposite leg at least 3 months prior to the current TKA
• willing to return for follow-up visits and should be willing and able to be transported from the UOC to the Skeletal Muscle Exercise Research Facility (SMERF), in the Department of Physical Therapy study site for scheduled research follow-up appointments

Exclusion Criteria:

• adult with previous additional orthopaedic, neurological, visual or surgical conditions that may affect gait or balance

Patients who present to the University of Utah for TKA surgical procedure