MRIs getting ordered for knee pain when x-rays would do just fine

Physicians treating possibly osteoarthritic patients 40 and older for knee pain can save these patients time, trouble and quite a lot of money—while sacrificing little to nothing on diagnostic accuracy—by sending them for weight-bearing x-rays rather than MRI scans.

So conclude researchers at Washington University in St. Louis and the St. Louis Center for Cartilage Restoration and Repair in a study running in the September edition of the Journal of the American Academy of Orthopaedic Surgeons.

Muyibat Adelani, MD, and colleagues prospectively followed 599 new patients as their orthopedic surgeons and sports-med docs documented four factors: the presence of a prereferral MRI and/or plain radiographic studies, the results of weight-bearing radiographs, treatment recommendations and the impact of any prereferral imaging.

The team found that 22 percent of the patients (130 of 599) arrived in the specialist ortho practice after receiving a prereferral MRI ordered by primary care physicians and other clinicians.  

Of these, 82 percent had not been first sent for weight-bearing x-rays.

That’s a red flag, as previous studies have shown weight-bearing plain radiographs provide an accurate means of assessing narrowing of joint spaces—and cost around 12 times less than MRI, the authors note.

It also turned out that 45 percent of the prereferral-MRI patients had significant loss of joint space, with 17 percent having lost more than half the space.

That threshold is considered a signpost of advanced osteoarthritis.

Most tellingly, the researchers found that 48 percent of the prereferral MRIs did not contribute to the ortho specialists’ treatment recommendations.

And, in patients with greater than 50 percent loss of joint space, Adelani and colleagues deemed MRI unnecessary in 95 percent of the cases.

Plain radiographic studies “can be sufficiently diagnostic of significant osteoarthritis, thus helping to avoid costly MRI studies,” the authors reiterate in their discussion.

“Educating physicians on the utility of weight-bearing radiographs, and secondarily, educating patients on the limited indications for MRI, may help to decrease the excessive use of advanced imaging,” they conclude.

The journal has posted the full study for free.