Eighty patients diagnosed with isolated medial and patellofemoral osteoarthritis were randomized to undergo a bi-compartmental knee arthroplasty (BCA; n=40) or total knee arthroplasty (TKA; n=40). Outcomes of interest included surgical time, blood loss, Oxford Knee Score (OKS), the Knee Society Score (KSS), range of motion (ROM), and the University of California, Los Angeles (UCLA) activity score which were all measured at baseline, 3 months, 6 months, 1 year, 2 year and 5 year post-operation. Furthermore, the Forgotten Joint Score (FJS), and the Timed-Up-and-Go Test (TUGT) were also evaluated at 5 year follow-up only. The results revealed that the OKS, KSS, UCLA activity score, TUGT, and FJS results were not statistically significantly different at any of the follow-up periods between the BKA and TKA groups (p>0.05 for all). However, the range of motion scores were statistically significantly greater in the BCA group at 6 months (p=0.02), 1 years (p=0.0016), and 2 years (p=0.001), and 5 years (p=0.003) post-operation. No cases of dislocation, fractures, or radiolucency were observed in either group.