Magnetic resonance signals in healing menisci: an experimental study in dogs.

This study examined the magnetic resonance imaging (MRI) signal from healing menisci in adult dogs. Complete, full-thickness radial tears were created in the medial menisci of adult dogs and allowed to heal spontaneously. Menisci were harvested and examined at 8, 12, and 26 weeks after injury using a spin-echo imaging sequence. After imaging, the menisci were processed for routine histologic examination. The results of the study demonstrated that the repair tissue consistently yielded an increased MRI signal as compared with the normal meniscal tissue. This increased signal persisted at 26 weeks even though the repair tissue had modulated from fibrovascular scar tissue into fibrocartilage. The results of this study confirm the clinical impression that normal fibrovascular repair tissue in the healing meniscus can emit persistently increased signals on MRI examination. However, the long-term history of these signals remains unknown.