Acute pes anserine bursitis: MR imaging.

PURPOSE: To determine the magnetic resonance (MR) imaging appearance of acute pes anserine bursitis.

MATERIALS AND METHODS: Four patients (aged 40-50 years) with presumed internal derangements of the knee underwent MR imaging; at that time, collections of fluid were found in the pes anserine bursa, but no other abnormalities were noted.

RESULTS: Pes anserine bursitis was clinically diagnosed in all four patients when MR findings and physical examination findings were correlated.

CONCLUSION: Pes anserine bursitis has a characteristic MR appearance of fluid beneath the tendons of the pes anserinus at the medical aspect of the tibia near the joint line. Pes anserine bursitis can clinically mimic an internal derangement of the knee, which can result in the performance of unnecessary arthroscopy. MR imaging can be useful in diagnosing pes anserine bursitis and obviating surgery.