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