ObjectiveTo systematically review the effects of unicompartmental keen arthroplasty (UKA) and total keen arthroplasty (TKA) in patients with unicompartmental osteoarthritis of the keen. MethodsWe electronically searched PubMed, MEDLINE (Ovid), ProQuest, EBSCO, The Cochrane Library (Issue 10, 2014), EMbase, CNKI, VIP, CBM and WanFang Data from inception to November 2014, to collect randomized controlled trials (RCTs) and cohort studies of UKA versus TKA for patients with unicompartmental osteoarthritis of the keen. Two reviewers independently screened literature according to the inclusion and exclusion criteria, extracted data and assessed the risk of bias of included studies. Then, meta-analysis was performed using RevMan 5.2 software. ResultsA total of 6 RCTs and 6 cohort studies involving 940 keens were included. The results of meta-analysis indicated that patients underwent UKA enjoyed a quicker rehabilitation to achieve a flexion of 90° (RCT:P<0.05; cohort study:SMD=-1.70, 95%CI -2.07 to -1.34, P<0.000 01), had better range of motion (cohort study:SMD=0.59, 95%CI 0.41 to 0.78, P=0), and were less likely to get DVT (RCT:RR=0.31, 95%CI 0.12 to 0.82, P=0.02), but the patients underwent UKA were more likely to have a revision (RCT:RR=7.59, 95%CI 1.76 to 32.85, P=0.007). The keen scores of the UKA group were similar to the TKA group (RCT:P=0.626; cohort study:MD=1.78, 95%CI -0.09 to 3.65, P=0.06). ConclusionCurrent evidence shows that, compared with patients underwent TKA, patients underwent UKA have a quicker rehabilitation and fewer rates of DVT, and are more likely to have a revision. The medium to long-term follow up result of keen scores in both groups was equivalent. Due to limited quality and quantity of the included studies, more high quality studies are needed to verify the above conclusion.