This is a single-center clinical trial started by the study team. The goal is to compare two surgeries for people who have a varus knee alignment and a tear at the back attachment of the medial meniscus. Researchers want to learn how the newer bone-cut procedure with arthroscopic meniscus repair compares to the standard bone-cut procedure with arthroscopic meniscus repair. Researchers will also track safety and hospital-related costs.

Main questions the study aims to answer:

• At 12 months after surgery, how does the improvement in knee function compare between the newer-surgery group and the standard-surgery group? The study will evaluate preliminary trends in clinical efficacy using the Lysholm knee function score.
• Do the two groups differ in pain relief, imaging findings, meniscus healing, complications, and hospital stay and preliminary cost-effectiveness? The study plans to enroll about 20 participants at Sun Yat-sen University Eighth Affiliated Hospital (Shenzhen Futian). Participants will be assigned by chance, like drawing lots, in a one-to-one ratio. This is an pilot study with a PROBE (Prospective Randomized Open-label Blinded-Endpoint) design. While participants and surgeons will know which surgery is performed, the research assistant responsible for collecting patient-reported outcomes will be blinded to group allocation to minimize observer bias.

Study groups:

• Experimental group: hemi-tibial plateau osteotomy plus arthroscopic meniscus repair.
• Control group: high tibial osteotomy plus arthroscopic meniscus repair.

Who may join:

• Age 35 to 65 years, with no restriction on sex;
• Diagnosed with a medial meniscus posterior root tear;
• Presence of varus knee deformity;
• Imaging findings support the diagnosis (e.g., knee MRI);
• Failure of conservative treatment: no meaningful improvement after more than 1 month of non-surgical management (e.g., rest, medication, or physical therapy);
• Varus alignment angle less than 10 degrees;
• The deformity is predominantly tibial in origin;
• Knee radiographs do not show the most severe osteoarthritis (Kellgren-Lawrence grade other than IV).

Who cannot join:

• A knee that is chronically "locked," meaning it cannot bend or straighten normally.
• The most severe level of knee arthritis on knee X-ray.
• Severe arthritis in the hip or ankle that could affect knee function testing.
• Inflammatory or infectious conditions that can affect the knee, or abnormal inflammation blood tests that make participation unsafe.
• Knee instability or poorly functioning prior ligament reconstruction, based on the study doctor's judgment.
• Any prior surgery on the target knee, or on other joints of the same-side lower limb.
• Serious heart, liver, or kidney disease, cancer, bleeding disorders, immune deficiency, or severe mental health conditions that make participation unsafe.
• Body mass index of 30 or higher.
• Pregnancy or breastfeeding, or not willing to use birth control during the study.
• Participation in another clinical study within the past 3 months (except registry studies).
• Any other reason the study doctor believes makes participation unsafe or not appropriate.

What participants will do:

• Complete screening and baseline assessments within about 30 days before surgery and sign informed consent.
• Receive the assigned surgery during the hospital stay.
• Return for follow-up visits at 3 months, 6 months, and 12 months after surgery.
• Complete knee function and symptom questionnaires and rate pain at each follow-up visit.
• Have standing knee X-rays and full-length leg X-rays at 3, 6, and 12 months.
• Have an MRI of the operated knee at 3, 6, and 12 months to assess meniscus healing and meniscus extrusion.

Outcomes:

• Primary outcome: change from baseline to 12 months in the Lysholm knee function score.
• Secondary outcomes: changes in the Lysholm score at 3 and 6 months; changes in the WOMAC knee arthritis symptom score at 3, 6, and 12 months; changes in pain rating on a standard pain scale at 3, 6, and 12 months; imaging measures and bone healing on X-rays; meniscus healing and extrusion on MRI; surgery time and blood loss; complications during and after surgery; length of hospital stay and hospital costs; and quality of life utility value from a standard health questionnaire.

Inclusion Criteria:

• Age 35 to 75 years, with no restriction on sex.
• Clinical features suggestive of a medial meniscus posterior root tear, including at least one of the following symptoms: knee locking, clicking, or medial knee pain; and at least one of the following signs: medial joint line tenderness or a positive McMurray test.
• Varus knee deformity with a varus angle of less than 10 degrees, with the deformity predominantly originating from the tibia (i.e., medial proximal tibial angle less than 87 degrees).
• Knee MRI demonstrates a medial meniscus posterior root tear.
• Knee radiographs show narrowing of the medial joint space, and Kellgren-Lawrence grade less than IV.
• Failure of conservative treatment (e.g., rest, medication, or physical therapy) for more than 1 month.
• Willing to accept randomization and able to understand and sign the informed consent form.
• For participants with bilateral deformity, the more severely deformed side will be selected as the operative (study) side.

Exclusion Criteria:

• Chronic knee locking (e.g., the participant cannot bend or fully straighten the knee).
• Kellgren-Lawrence grade IV knee osteoarthritis.
• Osteoarthritis or other conditions in other joints (e.g., hip or ankle) that may affect assessment of knee function.
• Known inflammatory diseases or other conditions that may affect knee function, including but not limited to: autoimmune diseases (e.g., rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, systemic lupus erythematosus); crystal-induced arthritis (gout, pseudogout); secondary knee osteoarthritis due to trauma or other diseases; active knee joint infection or a history of knee joint infection; reactive arthritis; systemic cartilage disorders; systemic connective tissue diseases; metabolic bone disease; fracture (acute or subacute fracture within 6 months prior to the screening visit); osteonecrosis; or abnormal inflammatory markers (C-reactive protein or high-sensitivity C-reactive protein at least 2 times the upper limit of normal, or erythrocyte sedimentation rate at least 3 times the upper limit of normal), if judged by the investigator to be unsuitable for participation.
• Target-knee instability (including but not limited to post-traumatic or congenital laxity) or inadequate ligament reconstruction, as judged by the investigator.
• Any prior surgery on the target knee or on other joints of the ipsilateral lower limb.
• Serious cardiac disease; hepatic impairment (aspartate aminotransferase or alanine aminotransferase at least 3 times the upper limit of normal, or total serum bilirubin at least 1.5 times the upper limit of normal); renal impairment (serum creatinine at least 1.5 times the upper limit of normal); other musculoskeletal disorders; malignancy; coagulation disorders; immunodeficiency; or psychiatric disorders, if judged by the investigator to be unsuitable for participation.
• Body mass index at least 30 kg/m².
• Pregnant or breastfeeding women, or participants (including men and women) unwilling to use contraception during the study period.
• Participation in another clinical study within 3 months prior to enrollment (excluding registry studies).
• Any other condition that, in the investigator's judgment, makes the participant unsuitable for participation.