A Prospective Study to Evaluate the ConforMIS iTotal® (PS) Knee Replacement System

Inclusion Criteria: * Clinical condition included in the approved Indications For Use for the iTotal® PS * Osteoarthritis, as confirmed by the investigator's assessment of disease status at screening visit that warrants a TKR procedure. Disease status is assessed by Clinical and Radiographic assessment. * Willingness to participate in the clinical study, to give informed consent, and to attend all follow-up visits * \> 18 years of age Exclusion Criteria: * Simultaneous bilateral procedure required * BMI \> 40 * Active malignancy (defined as a history of any invasive malignancy - except non- melanoma skin cancer), unless patient has been treated with curative intent and there have been no clinical signs or symptoms of the malignancy for at least 5 years * Poorly controlled diabetes * Neuromuscular conditions which prevent patient from participating in study activities * Active local or systemic infection * Immunocompromised * Fibromyalgia or other general body pain related condition * Rheumatoid arthritis or other forms of inflammatory joint disease * Loss of bone or musculature, osteonecrosis, neuromuscular or vascular compromise in the area of the joint to be operated on, to an extent that the procedure is unjustified * Diagnosed with or receiving treatment for Osteoporosis * Other physical disability affecting the hips, spine, or contralateral knee * Severe instability due to advanced loss of osteochondral structure * Prior arthroplasty of the affected knee, including High Tibial Osteotomy (HTO) * Unwilling or unable to comply with study requirements * Participation in another clinical study which would confound results * Allergy to any of the implant materials