Does only a mri confirm a meniscus tear? is there any other test to confirm that? locking knee joint when sitting and raise the knee straight

It's the best: A meniscus does not show on an x-ray. The history and physical exam can really help make the diagnosis. An arthrogram, dye and air injected into the knee used to be used to help decide if a tear is present or not. Painful test, often inconclusive, and frankly just about a lost art. An MRI is fast, painless, and rarely wrong. Mris are usually done prior to suggesting surgery.

MRI is the best test: While ultrasound can show a meniscal tear it is has lower specificity and some false-positive diagnoses. Therefore, to avoid unnecessary arthroscopy an orthopedic surgeon will likely want an MRI for more detailed anatomical evaluation of the knee, confirmation of the diagnosis, as well as possibly finding additional pathology that might go undetected by ultrasound.

Alternative: Although not as good in the evaluation of the ligaments and soft tissues surrounding the knee, an arthrogram with CT is almost as good for the diagnosis of meniscal tears and articular damage as an MRI. I disagree with other comments indicating an arthrogram is a painful procedure. Done properly, it is usually not more painful than a flu shot. Google "DrNefcy.com" and click on arthrogram advice.