Inclusion Criteria:  A disabled or severely disabled joint as a result of arthritis, traumatic arthritis, rheumatoid arthritis, poly-arthritis or avascular necrosis Patients between the age of 18 and 80 at the time of consent Listed for total knee replacement surgery. Patients who are willing and able 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 condralar structures or loss of integrity of the medial or lateral ligament 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