Fixed Bearing Versus Mobile Bearing Patient Satisfaction and Clinical Outcome Study

Inclusion Criteria: 1. Must be able to read, understand and provide written informed consent on the Institutional Review Board (IRB) approved Informed Consent Form (ICF) 2. Ability to understand and provide written authorization for use and disclosure of personal health information. 3. Subject who are able and willing to comply with the study protocol and follow-up visit. 4. Must be 18 years or older to participate. 5. Subjects must have a clinically documented Osteoarthritis in a knee, single or multiple compartments, 6. Subjects must have undergone a FB UKA or MB UKA in one and or both knees. MB UKA or FB UKA patients revised to Total Knee Arthroplasty (TKA) are eligible to enroll. 7. Must be a minimum 2 year (24 months) post-surgery on the knee. 8. The UKA operation must have been performed by the Investigator. 9. Subjects must be able to return for the follow-up appointment, and have the mental capacity to cooperate with PRO's, questionnaires, physical exam and imaging studies. Exclusion Criteria: 1. Subjects with Bicompartmental UKA (i.e. medical or lateral UKA combined with Patello Femoral Joint (PFJ) (UKA) 2. Women who are pregnant.