I recently got mri of my knee done. the result was " grade iii(a) tear in posterior horn of medial meniscus" please guide me ?

See an Ortho surgeon: An orthopedic surgeon can review the MRI and do a thorough physical examination to determine whether there is a need for surgery vs. Conservative treatment. Though there is some variation in the grading systems of meniscal signal abnormalities on mri, grade iiia usually means a simple tear.

See Orthopedist: A tear of the posterior medial meniscus, the most common area of occurence, may well need arthroscopic surgery - you should consult an orthopedic surgeon.