In vivo knee kinematics will be assessed for 20 subjects that have been implanted with a Total Joint Orthopedics Klassic knee system by Dr. Aaron Hofmann of the Hofmann Arthritis Institute's Center for Precision Joint Replacement. This is the location from which all participants will be recruited and where fluoroscopy data collection will occur. Participants will undergo fluoroscopic surveillance of their implanted knee using a C-arm fluoroscopic unit while performing a deep knee bend activity at least six months post-operatively.

Enrollment will be increased to 24 subjects to ensure that researchers acquire the necessary 20 usable datasets for analysis and also to account for any subjects that may drop out of the study. At present, all TKA available for surgeons to use are asymmetric where there is a distinct femoral and tibial component for the left knee and a distinct femoral and tibial component for the right knee. The Klassic knee system is a symmetrical knee implant, where the same femoral and same tibial component can be used for either the right or left knee. The kinematics for the 20 knees will be analyzed, including condylar roll-back, axial rotation, range of motion, and condylar lift-off

Inclusion Criteria:

1. Subjects will have a Klassic knee system.
2. Subjects must be at least six months post-operative.
3. Participants must be judged clinically successful with their most recent (new) Knee Society "Knee Score" equal to or greater than 80.
4. Participants must be able to perform a deep knee bend.
5. Subjects must be willing to sign the Informed Consent (IC) / HIPAA form to participate in the study.
6. Must speak English.

Exclusion Criteria:

1. 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.
2. Subjects without the required type of knee implant.
3. Bilateral subjects (i.e., patients with both knees implanted)
4. Subjects who are unable to perform a deep knee bend.
5. Subjects who are unwilling to sign Informed Consent/ HIPAA documents.
6. Subjects who do not speak English

Patients of Dr. Aaron Hofmann who have been implanted with the Klassic Knee System

Researchers would like to retain this study data in our secure database so as to continue to add relevant, current data to our digital collection to help us work with manufacturers in the future to create better implants that last longer and will not require revision surgery. Participants will be asked if their study data may remain a part of the University of Tennessee's Center for Musculoskeletal Research data collection for use in future studies in the IC. Identifiers are automatically removed by the secure server after data are uploaded.

at least 6 months post-operative