MRI can't tell whether knee cartilage can be fixed  

An MRI can diagnose a tear in the disc of cartilage cushioning the knee, but it does not reliably predict which tears can be repaired with surgery, a new study finds. 

It's estimated that more than 850,000 Americans undergo surgery each year for injuries to the menisci, two wedges of shock-absorbing cartilage in the knee joint. That surgery can involve either suturing the tear back together or removing the damaged portion of the meniscal tissue altogether. 

At present, surgeons cannot tell whether the tear will be reparable until the surgery is underway, though having such knowledge would be advantageous. 

For patients, it matters because repaired meniscus tears have a more involved recovery compared with surgical removal of the tissue. 

When the injured tissue is simply trimmed off, people can basically get up and walk home. They'll have some pain, but there are few restrictions on what they can do, and most can fully return to their usual physical activities within about two weeks. 

People who have the meniscal tear repaired, on the other hand, need about four to six weeks of recovery, often with physical therapy. 

So it would be nice to be able to tell patients ahead of time which surgery they are going to get, and unfortunately physicians are at a loss. 

MRI scans however are widely used to diagnose meniscus tears, and they are accurate up to 99 percent of the time. 

But that same MRI information has traditionally been considered a poor predictor of whether or not the tear can be repaired. While the imaging can show doctors that a tear exists in the meniscus, it is not good with the details -- where the tear begins and ends, or how complex it is. 

Recent debate about whether today's more advanced MRI technology might be better at predicting the reparability of meniscus tears prompted researchers to test the idea. 

In the study senior radiologists examined the MRI records of 119 patients who had already undergone surgery for a meniscal tear -- either a surgical repair or removal of the injured tissue. 

The radiologists tried to predict whether or not each tear could be fixed. 

They often got it wrong. One doctor was correct 63 percent of the time, and the other only 58 percent of the time. 

And when the researchers looked at the specific reparability "scores" each doctor gave the patients, they found that the radiologists were in agreement only 38 percent of the time. 

And this, folks, is why medicine is not an ‘exact science.’ 

According to the study authors, the two radiologists in the study are very experienced and "renowned" in their field. So it's likely that radiologists in community hospitals would also fare poorly if asked to predict the reparability of a meniscal tear. 

For now, patients having surgery for a meniscal tear will continue to have to wait until the procedure itself to know just what to expect afterward. 

Not all meniscal tears require surgery. Some people recover with simple measures like rest, ice and over-the-counter pain medication and physical therapy.