Truth Test for Knees?

Orthopedic surgeons have identified a molecular biomarker that could potentially help people with knee injuries save time, and money and the risks of surgery.

According to a study just published in The Journal of Bone and Joint Surgery researchers from California, Florida, Pennsylvania and New York have identified a biomarker found exclusively in patients with  torn cartilage.  Potentially, this simple test could help patients avoid the time and cost of undergoing an MRI and identify those who are candidates for surgery rather than those who have less operable conditions.

By analyzing the synovial fluid surrounding the knee joints of 30 patients with meniscal tears, researchers found a protein complex called fibronectin-aggrecan that wasn’t present in 10 volunteers with normal, pain-free knees.  To date, fibronectin-aggrecan has not been found in patients with osteoarthritis.

An estimated 700,000 arthroscopic knee operations are performed each year in the U.S. based on the results of MRI scans, which can cost in the region of $2,500.

While surgeons can use MRIs to try to discern the root of a patient’s knee pain, MRIs often cannot differentiate between inflammations from natural degeneration and a full-fledged tear.

Traumatic and degenerative injuries look the same on MRI,” said Gaetano Scuderi, Professor of  orthopaedic surgery at Stanford School of Medicine. “In a 50-year-old, we can’t tell the difference.”

However, correctly identifying a cartilage tear is only one obstacle. Sometimes, patients sustain pain  after corrective surgery because the tear is not actually the root of pain.

Sometimes you would think you did a great job but the patient still had pain,” Scuderi said. “Why did this  person not get better when another person did?”

Previous studies have shown that surgery is only effective for a torn meniscus or cartilage. Knee pain caused by age-related osteoarthritis or injured hip ligaments can resemble a torn meniscus but isn’t helped by surgery. This distinction isn’t always clear on MRI scans.

In a clinical setting, this new biomarker could effectively differentiate knees with pain-inducing cartilage tears that are responsive to surgery from knees with only natural cartilage degradation.

This would be especially beneficial to older patient populations in whom MRIs always show degeneration. The biomarker test offers a cheaper and more specific identification of pathology. Better still, the researchers are hoping to image the molecule non-invasively as opposed to aspirating it for assay.

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