A Trial of Mechanical Axis With Soft Tissue Release Balancing vs Functional Alignment With Bony Release Balancing in Total Knee Replacement Using Stryker's Mako Robot

This study is a prospective, randomized, longitudinal study of the clinical outcomes of osteoarthritis patients treated by two different alignment philosophies for total knee replacement. All patients will be treated with the same knee system, implanted using MAKO robotic-arm assisted technology.

Inclusion Criteria: * The patient is a male or non-pregnant female between the ages of 40-80 years. * The patient requires a primary total knee replacement and is indicated for robotic-assisted surgery. * Patient is deemed appropriate for a cruciate retaining knee replacement. * The patient has a primary diagnosis of osteoarthritis (OA). * The patient has intact collateral ligaments. * The patient is able to undergo CT scanning of the affected limb. * The patient has signed the study specific, ethics-approved, Informed Consent document. * The patient is willing and able to comply with the specified pre-operative and post-operative clinical and radiographic evaluations. Exclusion Criteria: * The patient has a history of total, unicompartmental reconstruction or fusion of the affected joint. * Patient has had a previous osteotomy around the knee. * The patient is morbidly obese (BMI ≥ 40). * The patient has a deformity which will require the use of stems, wedges or augments in conjunction with the Triathlon Total Knee System. * The patient has a varus/valgus deformity ≥ 15°. * The patient has a fixed flexion deformity ≥ 15°. * The patient has a neuromuscular or neurosensory deficiency, which would limit the ability to assess the performance of the device. * The patient has a systemic or metabolic disorder leading to progressive bone deterioration. * The patient is immunologically suppressed or receiving steroids in excess of normal physiological requirements. * Patient has a cognitive impairment, an intellectual disability or a mental illness. * The patient is pregnant. * The patient has metal hardware present in the region of the hip, knee or ankle (as this is known to create geometrical distortion in the region of the implant).