Valgus high tibial osteotomy (HTO) and unicompartmental knee arthroplasty (UKA) are established treatment options for patients with medial compartmental osteoarthritis (OA) of the knee.However, the clinical outcomes of these treatment modalities for unicompartmental OA have become subjects of debate.

Although HTO for the correction of malalignment in the medial osteoarthritic knee has been shown to provide successful outcomes in some studies, it is technically difficult to achieve the ideal valgus position postoperatively, and the likelihood of postoperative complications after HTO is greater than that after UKA . As compared with HTO, UKA has been reported to provide better long-term results, to have a shorter time to full weight bearing, to allow easier rehabilitation, and to have fewer perioperative complications. Furthermore, indications for UKA are broadening, including younger and more active patients, since encouraging midterm and long-term results were published.

Inclusion Criteria:

1. - Medial compartment osteoarthritis with exposed bone on both femur and tibia.
2. -Functionally intact Anterior Cruciate Ligament (superficial damage or splitting is acceptable)
3. -Full thickness and good quality lateral cartilage present
4. -Correctable intra-articular varus deformity (suggestive of functionally intact medical cruciate ligament) 5-Medically fit showing an American Society of Anesthesiologists (ASA) of 1 or 2

Exclusion Criteria:

1. Require revision knee replacement surgery.
2. Have rheumatoid arthritis or other inflammatory disorders.
3. Are unlikely to be able to perform required clinical assessment tasks.
4. Have symptomatic foot, hip or spinal pathology.
5. Previous knee surgery other than diagnostic arthroscopy and medial menisectomy.
6. Previously had septic arthritis.
7. Have significant damage to the patella-Femoral Joint especially on the lateral facet.