A Study to Evaluate the DePuy Minimally Invasive Unicompartmental Knee

Inclusion Criteria: * Male or female subjects, who are 40 to 75 years of age inclusive. * Subjects who are able to give voluntary, written informed consent to participate in this investigation and from whom written consent has been obtained. * Subjects who, in the opinion of the Investigator, are able to understand this investigation, co-operate with the investigational procedures and are willing to return to the hospital for all the required post-operative follow-ups. * Subjects who exhibit loss of articular cartilage which is predominantly confined to a single compartment. The remaining compartments must be intact and able to bear normal loads. * Subjects who in the opinion of the Clinical Investigator are considered to be suitable for treatment with the investigation device, according to the indications specified in the package insert leaflet. Exclusion Criteria: * Subjects who, in the opinion of the Investigator, have an existing condition that would compromise their participation and follow-up in this study. * Subjects with a known history of poor compliance to medical treatment. * Women who are pregnant. * Subjects who are known drug or alcohol abusers or with psychological disorders that could effect follow-up care or treatment outcomes. * Subjects who have participated in a clinical study with an investigational product in the last month. * Subjects who are currently involved in any injury litigation claims. * Revision of an existing unicompartmental implant. * Subjects who have gross ligament laxity / instability. * Subjects who have an inflammatory joint disease * Subjects in whom there is evidence of previous joint sepsis * Subjects who have a pre-operative flexion contracture of 15° or greater * Subjects who have a pre-operative flexion of less than 90° * Subjects who have a pre-operative limb deformity of greater than 15° varus or valgus * Subjects who have morbid obesity i.e. BMI \> 40%