Clinical Outcome and OR Resource Use of Total Knee Arthroplasty Using Patient-Specific or Conventional Instrumentation

Inclusion Criteria: * Painful, disabled knee joint resulting from osteoarthritis requiring primary TKA * Informed Consent: Patient has signed a "Patient Informed Consent. * Able and willing to undergo a preoperative MRI scan (for PSI cases) and full-leg, standing radiographs (all cases) * Able and willing to follow instructions and complete follow-up * Patient receiving Zimmer NexGen Solutions CR-Flex (including Gender Solutions) Exclusion Criteria: * Patient is skeletally immature * Active Infection (including septic knee, distant infection, or osteomyelitis) * Severe hip arthrosis * Neurological disorders (including, but not limited to Parkinson's disease) * Prior unicompartmental knee arthroplasty, TKA, knee fusion or patellectomy * Hip or knee ankylosis * Either rheumatoid or post-traumatic knee arthritis * Scheduled for simultaneous bilateral TKA * Indications of intra- and/or extra-articular deformations that would inhibit the use of PSI guides * Any metal within 150 mm of the joint line for the operative-side knee * Knee deformities greater than 15 degrees of fixed varus, valgus, or flexion contracture on initial physical examination * An existing condition that would, in the opinion of the investigator, compromise participation or follow-up in this study * A female who is pregnant or lactating * Current involvement in any personal injury litigation, medical-legal or worker's compensation claims * Arterial disease or stents that would exclude the use of a tourniquet