Do i expect to have surgery same day as mri if i have a meniscus tear? or would i have to wait? i need to figure this out before prom.

Waiting period: Usually it takes time to read the mri, and to schedule the surgery. Best talk to the doctor to find out his plans.

Not emergent: While it would be nice to have surgery the same day as an mri, it usually takes some number of days to get the MRI back, read by the radiologist or surgeon, determine if surgery is appropriate, and then schedule surgery. Surgery can be done soon, or it can be delayed for a period of time if your symptoms are manageable (and the tear is not too large).