Radiologic signs more than double sensitivity of MR imaging of knee

Radiologists can make a more accurate preoperative diagnosis of damage to knee cartilage by using four radiologic signs, according to a study from Duke University Medical Center. Using the signs to identify the extent and type of damage to knee cartilage makes interpreting MRI with a higher degree of accuracy easier for any radiologist, regardless of level of expertise.

Reviewers correctly identified 17 of 19 radial meniscal tears (89%) using the four radiologic signs: the truncated triangle, cleft, marching cleft, and the ghost meniscus. Each of these signs describes a unique type of tear and damage to the cartilage of the knee. These types of tears are categorized based on easily recognizable patterns that show up on MRI (AJR 2005;185;1429-1434).

A meniscal tear exposes the underlying cartilage of the knee and can lead to accelerated wear and arthritis from the decreased structural integrity of the knee joint. Fortunately, some types of meniscal tears can be repaired. Radial tears, however, are frequently irreparable, and even a relatively small radial tear can lead to advanced wear, said lead author Dr. Keith Harper, a musculoskeletal radiologist at Duke.

"It is advantageous to preoperatively identify potentially nonrepairable meniscal tears, such as radial tears," Harper said. "When possible and practical, repairing the damaged cartilage is significantly preferred to its removal."

Since treatment of meniscal tears is dependent on their configuration, size, and location, the characterization of the tear can help the surgeon and patient decide what type of surgery is necessary as well as what type of rehabilitation will be needed.

Radiologists can look for and easily recognize the four radiologic signs to prospectively identify radial tears. Using the signs increased the prospective characterization and sensitivity for the detection of radial tears from 37% to 89% in the study.

"We feel that by using the four signs, most radiologists who interpret knee MRIs should have a high degree of success of prospectively identifying radial meniscal tears," he said. "Since using the four signs is fairly easy, similar degrees of accuracy can be achieved by radiologists who may not be experts in the field of musculoskeletal radiology."

Harper said that they were surprised to find that the knowledge of specific and more objective signs for radial tears was a great help even for musculoskeletal radiologists with extensive experience interpreting knee MRIs.

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