How can knock knee be treated?

Depends on problem: Knock knee is normal in many people. Therefore, it is only treated if it is painful and usually this is the case when the outside joint compartment (lateral compartment) is worn down, and this is corrected as a pathologic condition with partial or total knee replacement. Unloader braces can help if this is due to arthritis but you need two braces for both knees.

Possible osteotomy: To add to dr. Beuchel's answer, in some younger patients who do not have arthritis, and have meniscus deficiency, a varus producing femoral osteotomy is usually performed. An osteotomy is when the femur bone is cut above the knee and realigned me to make it straight. While it seems like a big deal, the surgery is well tolerated, and healing takes place in 3months or so. Surgery should be performed usually by a sports medicine orthopedist or knee specialist.