Retrospective Simplex High Viscosity (HV) Bone Cement Study

Inclusion Criteria: * The Patient is age 18 or over at time of study device implantation * Patients who have undergone primary Triathlon Total Knee Arthroplasty in which Simplex HV/Simplex HV Gentamicin was indicated for fixation and used on label * Patients who have been followed for at least 24 months postoperatively Exclusion Criteria: * Patients who have undergone revision surgery * Patients who have undergone bilateral Knee Arthroplasty * Patients contraindicated for either the devices implanted, or the cement used, according to medical history review and instructions for use * Patient has a cementless tibial baseplate. * Patient has an active or suspected latent infection in or about the affected knee joint * Patient has muscle loss or neuromuscular impairment in the affected limb that would create an unjustifiable risk * Patient is immunologically suppressed or receiving steroids in excess of normal physiological requirements (e.g. \> 30 days) * Patient has a known hypersensitivity to any of the cements constituents or in patients with severe renal failure * Patient is a prisoner