I had a serious meniscus tear which went undiagnosed for almost a year because an idiot doctor didn't think, even with all my symptoms, it might not hurt to do an MRI. The second tear could have likely been prevented if I'd gotten the first one taken care of. Both tears showed up clearly with the MRI.
There is nothing good that can come of doing high impact sports when you have torn/damaged cartilage in your knee.
While the MRI is not the be-all end-all solution, and I am blessed with excellent health insurance, it's a valuable diagnostic tool, and had it been used sooner, would have saved some of my knee cartilage.
More importantly, find a good doctor!