Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association
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Patients who have hip joint diseases sometimes complain of knee pain as well as hip joint area pain. However, the precise sensory innervation pattern and correlation of the sensory nerves of the hip joint and knee are unknown. The purpose of this study was to investigate dorsal root ganglion (DRG) neurons with dichotomizing axons projecting to both the hip joint and the knee skin in rats using double fluorescent labeling techniques, and to examine characteristics of the DRG neurons with dichotomizing axons using immunohistochemical staining for inflammatory neuropeptides such as calcitonin gene-related peptide (CGRP). ⋯ Our results showed that the double-labeled neurons had peripheral axons that dichotomized into both the hip joint and the knee skin. CGRP-positive neurons of these dichotomizing fibers may play some role in the manifestation of referred knee pain with hip joint pain.