The purpose of this study is to evaluate the clinical functional results of the Triathlon All-Polyethylene Tibia Knee Device.

This study is a retrospectively enrolled, prospective evaluation of the Triathlon All-Polyethylene Tibia (APT) for patients who meet the eligibility criteria. The enrolled cases will be followed for outcomes measured to 10 years. A modular, Triathlon metal-backed tibia (MBT) and polyethylene insert construct will be used as a historical control.

Inclusions:

• Patient underwent primary TKA and is currently implanted with the Triathlon All-Polyethylene Tibia as well as compatible Stryker femoral and patellar components with no pending revision or removal.
• Patient has signed an IRB-approved, study specific Informed Patient Consent Form.
• Patient is a male or non-pregnant female and is 18 years of age or older at the time of study device implantation.
• Patient is willing and able to comply with postoperative scheduled clinical and radiographic evaluations.

Exclusions:

• Patient had an active or suspected latent infection in or about the affected knee joint at time of study device implantation.
• Patient had distant foci of infection which could have caused hematogenous spread to the implant site at time of study device implantation.
• Patient was skeletally immature at time of study device implantation.
• Patient has a mental or neuromuscular disorder which would create an unacceptable risk of prosthesis instability, prosthesis fixation failure, or complications in postoperative care.
• Patient's bone stock was compromised by disease, infection, or prior implantation which cannot provide adequate support and/or fixation to the prosthesis.
• Patient had severe instability of the knee joint secondary to the absence of collateral ligament integrity and function.
• Patient was immunologically suppressed or receiving steroids in excess of normal physiological requirements at the time of surgery (e.g. > 30 days duration of treatment).
• Patient is a prisoner.