LAUSR

Background Loose bodies are one of the most frequently seen pathological processes observed in the knee joint. Just as loose bodies may settle within the knee joint cavity, they may also be localized within recesses and bursae. Purpose To determine in which anatomic localizations and at what frequencies loose bodies were located in recesses and bursae within the knee joint. It was also aimed to review the radiological anatomy of the common and unusual knee joint synovial recesses and bursae including arthroscopic blind spots on MRI. Material and Methods A total of 145 loose bodies in 104 knees evaluated by MRI were identified. The locations of loose bodies around the knee joint were divided into 11 groups and some of these groups were divided into specific subgroups on MRI. The anatomic localizations, the number, and dimensions of loose bodies were determined. Results There were 145 loose bodies and 45 patients had one, 19 patients had two, and 40 patients had three or more loose bodies in different locations. The average size of loose bodies was 9.3 mm (range = 9–23 mm). Posterior cruciate ligament recess was the most frequent location; the subpopliteal recess was the second and posterior femoral recess was the third most common location for the loose bodies. Conclusion The correct identification, the number, size, and anatomic localization of loose bodies on MRI is critical in the determination of the appropriate treatment and, thus, the development of osteoarthritis can be prevented. Loose bodies were mostly localized in the posterior, primarily in the posterior cruciate ligament recess, most were multiple and < 1 cm.