In Vivo Kinematics for Subjects Having a MicroPort Medial Pivot or DePuy Attune PCR TKA

Inclusion Criteria: * Subjects will have either a MicroPort Medial Pivot or DePuy Attune PCR TKA. * Subjects must be at least six months post-operative. * Participants must be judged clinically successful based on the surgeon's evaluation and their Forgotten Knee Score. * Participants must be able to perform the required activities - stepping up and a deep knee bend. * Subjects must be willing to sign the Informed Consent (IC) / HIPAA form to participate in the study Exclusion Criteria: * Pregnant, potentially pregnant or lactating females. To satisfy radiation protocol, each female subject will be asked if she is pregnant, or possibly could be pregnant. A pregnant person will not be allowed to participate in the study. * Subjects without one of the two types of knee implants under investigation. * Subjects who are unable to perform stepping up and deep knee bend. * Subjects who are unwilling to sign Informed Consent/ HIPAA documents. * Does not speak English.