Expensive MRIs Often Unnecessary for Knee Pain Diagnosis

Bridget M. Kuehn

September 19, 2016

Expensive and time-consuming magnetic resonance imaging (MRI) is often unnecessary to diagnose the cause of knee pain in patients age 40 years or older, according to a study published in the September issue of the Journal of the American Academy of Orthopaedic Surgeons. In fact, the study found that cheaper weight-bearing X-rays often are sufficient.

"Plain radiographic studies can be sufficiently diagnostic of significant osteoarthritis, thus helping to avoid costly MRI studies," write Muyibat A. Adelani, MD, an assistant professor of orthopaedic surgery at the Washington University School of Medicine in St. Louis, and colleagues. "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."

Knee pain is a common complaint among patients as they age, and many general physicians order MRIs to help diagnose the cause. However, MRIs can cost more than 12 times as much as plain X-ray, and may not provide useful clinical information, the authors note. Moreover, MRIs often turn up incidental findings, such as meniscal tears, that may not contribute to pain in middle-aged patients with osteoarthritis.

"Plain radiographic studies can often demonstrate advanced osteoarthritis, thereby identifying those patients in whom knee MRI is likely to provide little clinical value," the authors write.

Yet, previous retrospective studies have demonstrated that few patients with knee pain have a weight-bearing X-ray before receiving an MRI. In addition, most of the MRIs ordered by primary physicians were not considered necessary by orthopedic surgeons.

In the current prospective study, Dr Adelani and colleagues analyzed the value of prereferral imaging and its effect on treatment for 599 new patients age 40 years or older who were referred to an academic orthopedic surgery practice in St. Louis.

The most common diagnosis were osteoarthritis, in 39% of patients, and meniscal tear in 29%, according to the orthopedic specialists (orthopedic surgeons and sports medicine physicians).

Nearly 1 in 4 of the patients (130 of 599) had a prereferral MRI. Among those patients, the most common diagnoses were meniscal tear (38%) and osteoarthritis (37%).

However, only 76 (58%) of these individuals had a plain radiographic X-ray before the MRI, and just 17 (13%) had a weight-bearing X-ray. Yet, the specialist evaluations showed that 45% of these patients had evidence of joint space loss and 17% had lost more than half of their joint space, an indication of advanced osteoarthritis.

According to the orthopaedic specialists, only 48% of the prereferral MRIs provided information that helped guide treatment recommendations. In particular, MRIs were deemed unnecessary for 95% of the patients who had lost more than half of their joint space.

"Patients should always get weight-bearing X-rays before getting an MRI because MRIs are not always needed to diagnose knee problems," Dr Adelani said in an accompanying news release. "In cases where arthritis is suspected, weight-bearing X-rays often are more than enough for orthopedists to complete the diagnosis and treatment plan," the release continued.

The authors note their study has several limitations, including that it was a one-site study and used very strict exclusion criteria that may have resulted in an underestimation of prereferral MRIs.

Dr Adelani has disclosed no relevant financial relationships. Dr Mall, Dr Smith, or an immediate family member of theirs has made paid presentations for Arthrex or is a part of the company's speaker's bureau. Dr Brophy or an immediate family member has stock or stock options in Ostesys.

J Am Acad Orthop Surg. 2016;24:653-659. Full text

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