This review examined the literature regarding high tibial osteotomy (HTO) and unicompartmental knee arthroplasty (UKA), focusing on indications, survivorship and functional outcomes of the two procedures, as well as revision to total knee arthroplasty (TKA) after failed HTO or UKA. HTO and UKA share the same indications in selected cases of medial unicompartmental knee arthrosis. These indications include patients who are: 1) 55 to 65 years old; 2) moderately active; 3) non-obese; 4) have mild varus malalignment; 5) no joint instability; 6) good range of motion; and 7) moderate unicompartmental arthrosis. Few studies are available in the literature comparing the outcomes of HTO and UKA. Those few studies show slightly better results for UKA in terms of survivorship and functional outcome. Nevertheless, the differences are not remarkable, the study methods are not homogeneous and most of the papers report on closing wedge HTOs. For these reasons, no definitive conclusions can be drawn. TKA represents the revision option for both treatments and yields satisfactory functional outcomes and survivorship. Whether revision HTO and UKA-to-TKA perform any worse than primary TKA is still controversial. With the correct indications, both treatments produce durable and predictable outcomes in the treatment of medial unicompartmental arthrosis of the knee. There is no evidence of superior results of one treatment over the other.