Purpose: This study was conducted to define what portion of the normal popliteus musculotendinous unit can be visualized during standard diagnostic arthroscopy.
Methods: Knee arthroscopy was performed on 5 fresh-frozen cadaveric human knees by use of standard anterolateral and anteromedial portals. The most proximal and distal portions of the popliteus that could be visualized were tagged with arthroscopic sutures. The knees were subsequently dissected, and 4 measurements were made per specimen: the total length of the popliteus tendon; the length of the popliteus tendon that was able to be visualized; the extrasynovial segment at the femoral attachment, which was unable to be visualized; and the distance from the distal-most visible point of the tendon to the musculotendinous junction of the popliteus.
Results: The mean total length of the popliteus tendon was 42.0 mm. The arthroscopically tagged portion of the popliteus tendon that was able to be visualized averaged 18.2 mm, or 43.8% of the tendon length. The mean distance from the musculotendinous junction to the visualized portion was 15.1 mm, or 35.8% of the total tendon length. The mean distance from the most proximal visualized portion of the tendon to the femoral attachment was 8.7 mm, or 20.4% of the total tendon length. The musculotendinous junction was not arthroscopically visible in any specimen.
Conclusions: On standard knee arthroscopy, less than half of the normal popliteus tendon is visible, and the femoral insertion and musculotendinous junction are not visualized. Because most reported popliteus injuries have occurred here, reliance on arthroscopic visualization alone is inadequate.
Clinical relevance: The limitations of arthroscopic visualization of the normal popliteus tendon have implications for the diagnosis and treatment of posterolateral corner injuries.