Diagnostic Imaging
of Meniscal Injuries

By G. Patrick Thomas, Jr., DC, DACBR

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Radiographic examination of the knee is often unrewarding, despite physical and orthopedic findings that clearly indicate an abnormality.  Much of the supporting anatomy of the knee is invisible with conventional radiography, but more sophisticated techniques can be used to demonstrate these important structures.  Magnetic resonance imaging is able to delineate the cruciate ligaments and menisci, providing the clinician a more complete and accurate view of the patient’s condition.

Meniscal injuries are common, and lead to symptoms such as crepitus and joint locking.  Because of their lack of a blood supply, injured menisci do not heal well, and tend to progression.  The spectrum of meniscal injuries ranges from mild internal degeneration to frank tears.  A convenient grading system is used to describe meniscal injuries as seen with MRI.

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Normal: The normal meniscus is a uniformly dark triangle with a sharp apex directed horizontally.
 
 
 
 

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Grade I tears are identified as a small focal area of increased signal intensity on T2-weighted images.  The area of abnormality does not extend to the joint surface.  The clinical significance of these injuries is questionable, but they may progress to more serious tears.

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Grade II injuries manifest as linear areas of increased signal intensity, with no extension to the joint surface.  They are similar to Grade I tears both clinically and in regards to their significance for progression.
 

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Grade III: This meniscal injury extends to the joint surface, and is associated with overt symptoms such as ‘popping’ and locking.  Untreated, they are likely to progress to Grade IV tears.
 
 
 

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Grade IV injuries are characterized by fragmentation of the meniscus, and like the Grade III tear frequently produce crepitus and joint locking.
 
 
 

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Clinical Management

Grade I and II meniscal injuries are probably best treated conservatively.  It is important to identify and treat these injuries.  Without proper care they may progress to more advanced tears. 

Grade III and IV tears may require surgical intervention.  The alteration of the articular surfaces may precipitate or hasten the development of degenerative changes in the affected joint. 

Meniscal injuries are common, and often go undiagnosed because of the lack of specific finding seen with conventional radiography.  MRI is a very effective tool for demonstrating lesions of the menisci, giving the treating clinician much more information about his patient than radiographs alone. 

References

1.  Edelman R and Hesselink J: Clinical Magnetic Resonance Imaging, Philadelphia, WB Saunders, 1990
 

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This article first appeared in the December 2001 issue of Missouri Chiropractor.

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