X-rays best for diagnosing knee pain in patients aged older than 40
Knee pain is a common complaint among middle-aged patients and may lead to other complications. The use of MRI scans to diagnose knee pain is increasing, but many of the changes caused by degenerative diseases can appear on X-rays as well. A group of researchers sought to find which of the two is the best screening tool for knee pain.
Their findings seem to suggest that X-rays (radiographs) are useful for patients who do not get any help by an MRI. But, it is not clear how they draw that conclusion and the math gets a bit murky.
According to Muyibat Adelani, MD, an orthopaedic surgeon with Washington University’s Department of Orthopedics and lead author of this study, "Whether a patient will need surgery for knee problems depends on how much arthritis he or she has. If an X–ray shows that a person has significant arthritis, the MRI findings – like a meniscus tear – are less important because the amount of arthritis often dictates the treatment. Therefore, patients should always get a standing X–ray before getting an MRI to screen for knee pain in patients older than 40."
In the study, the authors looked at 100 knee MRIs from patients 40 and older and observed the following: The most common diagnoses are osteoarthritis (39%), and meniscal tears (29%). Nearly, one in four MRIs were taken prior to patient’s first having obtained a weight-bearing X-ray. Only half of those MRIs obtained prior to meeting with an orthopaedic surgeon actually contributed to a patient’s diagnosis and treatment for osteoarthritis.
Dr. Adelani said, “Patients should always get weight–bearing X–rays before getting an MRI because MRIs are not always needed to diagnose knee problems." In many cases where arthritis is suspected, weight bearing X–rays are more than enough for orthopaedists to complete the diagnosis and treatment plan. An appropriately timed consultation with an orthopaedic surgeon can be more cost effective than first obtaining MRI scans.
Thus, the study’s authors suggest that while MRI may help physicians diagnose problems that may be causing the knee pain, an x-ray is the best first line screening tool.