The purpose of this study is to measure the changes in the medial and lateral meniscus extrusion of the knee joint before and after surgery using ultrasound in patients who undergo medial opening wedge high tibial osteotomy, and examine the differences.

High tibial osteotomy (HTO) is an established treatment method for medial compartment osteoarthritis with varus knee deformity in a relatively young patient group. Excellent outcomes of HTO have been reported. However, about 10-30% of patients are not satisfied with the results after surgery. After proximal tibial osteotomy, studies on the factors of dissatisfaction have been actively conducted, but studies on the medial and lateral meniscus extrusion, which can be the cause, are insufficient. The relationship between the prolapse of the medial meniscus and articular cartilage is already well known and is known as an important factor in the progression of arthritis. As such, the association between the knee joint with meniscus extrusion and the general knee joint has been studied, but the effect on the clinical outcome after proximal tibial osteotomy has not been studied. Therefore, in this study, the investigators are planning to investigate the differences in clinical outcomes such as the degree and change of medial and lateral meniscus extrusion through non-invasive ultrasound examination before and after surgery in patients who undergo medial open proximal tibial osteotomy.

This study will enroll the patients with knee medial compartment osteoarthritis of the knee joint who undergo open proximal tibial osteotomy. The degree of medial and lateral meniscus extrusion will be measured through ultrasound measurements before and after surgery. Also, demographic factors and radiographic measurements will be also investigated before and after surgery. In addition, preoperative, postoperative 3, 6, and 1 year clinical results including meniscus extrusion will be compared and judged, and the evaluation will be evaluated by an orthopedic surgeon who has not participated in the operation among registered researchers.

Inclusion Criteria:

• Adults over 20
• Medial compartment knee osteoarthritis patients for Medial Opening Wedge High Tibial Osteotomy
• Patients who are willing or able to follow doctor's instructions, including joint exercises
• Patients who have received sufficient explanation for this clinical trial and agreed to participate

Exclusion Criteria:

• Patients with secondary knee osteoarthritis
• Patients with inflammatory arthritis or crystalline arthritis
• Local infection to the lower extremities of the pain area, sepsis, or previous neurological abnormalities.
• Patients with knee range of motion less than 90 degrees
• Patients with BMI above 40

Medial compartment knee osteoarthritis patients for Medial Opening Wedge High Tibial Osteotomy