Patients with inflammatory arthritis.

Patients that are morbidly obese, body mass index (BMI) \> 40.

Patients with a history of total or unicompartmental reconstruction of the affected joint.

Patients that have had a high tibial osteotomy or femoral osteotomy.

Patients with neuromuscular or neurosensory deficiency, which would limit the ability to assess the performance of the device.

Patients with a systemic or metabolic disorder leading to progressive bone deterioration.

Patients that are immunologically compromised, or receiving chronic steroids (\> 30 days).

Patients bone stock is compromised by disease or infection, which cannot provide adequate support and/or fixation to the prosthesis.

Patients with knee fusion to the affected joint.

Patients with an active or suspected latent infection in or about the knee joint.

Patients that are prisoners.

Medacta GMK Sphere® Multicenter Post-Market Outcomes Study