Evaluation of Outcomes of the Triathlon Hinge Knee (THK) System

Inclusion Criteria: * The subject undergoes a primary or revision procedure implanting at least the Revision Baseplate portion of the Triathlon Hinge Knee System in accordance with the Indications for Use. * The subject has signed an Institutional Review Board (IRB)/Ethical Committee (EC)-approved, study-specific Informed Consent Form (ICF). * The subject is a male or non-pregnant female at the time of enrollment. * The subject agrees to comply with the protocol-mandated clinical evaluations. Exclusion Criteria: * Any active or suspected latent infection in or about the knee joint; overt infection; * Distant foci of infection which may cause hematogenous spread to the implant site; rapid disease progression as manifested by joint destruction or bone resorption apparent on roentgenogram; * skeletally immature patients; * Severe instability of the knee joint secondary to the absence of collateral ligament integrity and function. * Bone stock compromised by disease, infection or prior implantation which cannot provide adequate support and/or fixation to the prosthesis. * Known or suspected sensitivity and/or allergy to any material in the device. * Conditions presenting an increased risk of failure include: * uncooperative patient or patient with neurologic disorder, incapable of following instructions; * osteoporosis; * metabolic disorders which may impair bone formation or cause bone loss; * osteomalacia; and, * previous arthrodesis. * A higher incidence of implant failure has also occurred in paraplegics, cerebral palsy and patients with Parkinson's disease. * Any mental or neuromuscular disorder which would create an unacceptable risk of prosthesis instability, prosthesis fixation failure, or complications in postoperative care. * The subject is a prisoner