Vascular anatomy of the lateral meniscus with special focus on the joint capsule.

Previous studies have reported that the lateral meniscus (LM) has two regions, the popliteal hiatus area (PH) with a scarce blood supply and the roots with an abundant one. However, the description of its vascular anatomy remains insufficient. We hypothesized that the difference in the width of the meniscus hilum (MH) affects the scarcity and abundance of blood supply to the LM. The MH is a concept proposed by us and is the only site of entrance or exit of blood vessels and nerves associated with the meniscus. The purpose of this study was to provide a structural explanation for the disparity of blood supply to the LM using the concept of MH. Sixteen knees were examined to investigate the blood supply to LM. In most areas, the femoral joint capsule (FJC) and tibial joint capsule (TJC) continued to the cranial and caudal edges of the LM, respectively. In the roots, the FJC and TJC covered the femoral and the outer-femoral surfaces. In contrast, the FJC in the PH did not attach to the cranial edge and only the TJC there did to the caudal edge of the LM. Histochemical examination showed that the blood vessels enter the LM via the MH. In the PH, the MH at the caudal edge was extremely narrow; and in the roots, the MH on the outer-femoral surfaces was wide. The results suggest that the difference in the width of the MH affected the scarcity and abundance of blood supply to the LM.