My wife has 6 week old medial meniscus root tear in knee (mri). Symptoms have been unique. No pain in knee but thigh and ankle muscles seize up if she walks 50ft+ or sits for 60mins. Any advice/ideas?

Therapy. Not every meniscus tear needs surgery. I would rec physical therapy for this as a first step.
Consider PT. If there is no knee pain, swelling or locking, then choose conservative (nonsurgical) management. Consider pt to address the strength and flexibility of those muscles around the knee joint. Her gait could be altered because of the meniscus tear.
See Knee Specialist. Symptoms seem significant and may require surgery to correct. Best approach in that case is minimally invasive arthroscopic surgery. The orthopedic surgeon who is a knee specialist can best serve you with an exam and opinion.

Related Questions

What can be done if a knee MRI comes back negative but the patient is still having problems? Can a MRI miss a medial meniscus tear? Please explain

Yes. Yes it can miss about 8-10% of the meniscal lesions, as well chondral lesions are generally missed, rather frequently. I would advise you to see your orthopod who can examine you and then decide on the diagnosis. Good luck. Read more...
See below. If done on the appropriate MRI scanner meniscal tears are usually diagnosed on mri. Pain can be from many causes, not just meniscal tear. It can come from joint effusion, synovitis, cartilage damages, baker's cyst, etc. Read more...
MRI. Mri can under estimate joint surface cartilage changes that cause pain. Referred pain from vascular or sciatic etiology may also be the culprit. Check with your orthopedic surgeon. Read more...