Inclusion Criteria:  Male or female of at least 18 years of age at the time of screening. Signed an institutional review board approved informed consent. Willingness and ability to comply with the study procedures and visit schedules and ability to understand and follow oral and written post-operative care instructions.  Previous medical diagnosis/ history of at least one of the following conditions requiring treatment using the Persona Revision Knee System within a pre-specified study variant configuration (cohort), in accordance with the instructions for use (IFU):  Rheumatoid arthritis, osteoarthritis, traumatic arthritis or polyarthritis Collagen disorders, and/or avascular necrosis of the femoral condyle Post-traumatic loss of joint configuration, particularly when there is patellofemoral erosion, dysfunction or prior patellectomy Moderate valgus, varus, or flexion deformities The salvage of previously failed surgical attempts or for a knee in which satisfactory stability in flexion cannot be obtained at the time of surgery A pre-operative Knee Society Knee Score (objective assessment) ≤ 80.  Exclusion Criteria:  Presence of clinically observed active or suspected latent infection in the affected joint at the time of procedure. Previous history of infection in the affected joint that may affect the prosthetic joint. Presence of or history of local/systemic/distant focal infection that may affect or hematogenously spread to the prosthetic joint. Skeletal immaturity or insufficient bone stock on femoral or tibial surfaces which cannot provide adequate support and/or fixation to the prosthesis. Diagnosed with neuropathic arthropathy, osteoporosis, or any loss of musculature or neuromuscular disease that compromises the affected limb. Presence of a stable, painless arthrodesis in a satisfactory functional position in the affected joint. Severe instability of the affected joint secondary to the absence of collateral ligament integrity.  Diagnosis of rheumatoid arthritis in conjunction with any of the following at the time of screening:  An ulcer of the skin History of recurrent breakdown of the skin Use of steroids Patient requires simultaneous bilateral knee surgery for treatment of diagnosed condition. Pregnant or women planning to become pregnant during the time they will be participating in the study. Any documented clinically significant degree of cognitive impairment or other condition, finding, or psychiatric illness at screening which, in the opinion of the Investigator, could compromise patient safety or interfere with the assessment of the safety and treatment effects of the study procedure. Any patient who is institutionalized, or with a known drug or alcohol dependence currently or within the last year.