Each patient will undergo a preoperative MRI of their affected knee joint to identify existing pathology (e.g. meniscal tears, loose bodies, chondral flaps). The results of the MRI will not be revealed to physicians, patients or data collectors. This will ensure that we have information on the existing joint pathology within each group and that prognostic variables between groups were sufficiently balanced (i.e. comparable rates of similar pathology per group). The primary outcome measure is self-reported quality of life (WOMAC). Secondary measures include self-reported functional ability (LEFS), swelling, pain and frequency of analgesic use (patient diary), and general health (SF-36). Assessments will take place preoperatively and at 3, 6 and 12 months postoperatively.