The Medacta International GMK Sphere Post-Marketing Surveillance Study

Inclusion Criteria: * A disabled or severely disabled joint as a result of arthritis, traumatic arthritis, rheumatoid arthritis, poly-arthritis or avascular necrosis * Patients must be between the age of 18 and 80 at the time of consent * Listed for total knee replacement surgery. * Patients who are willing to give informed written consent Exclusion Criteria: * Progressive local or systemic infection * Muscular loss, neuromuscular disease or vascular deficiency of the affected limb, making the operation unjustifiable * Severe instability secondary to advance destruction of condylar structures or loss of integrity of the medial or lateral ligament * Any patient who cannot or will not provide informed consent for participation in the study * Those whose prospects for a recovery to independent mobility would be compromised by known coexistent, medical problems * Patient whose BMI exceeds 40 * Any case not described in the inclusion criteria