Axonal profiling of the common fibular nerve and its branches: Their functional composition and clinical implications

The articular branch (Arb) from the common fibular nerve (CFN) plays a pivotal role in procedures such as genicular nerve blocks since it extensively innervates the anterolateral knee joint. It remains unclear whether the Arb can be classified as purely sensory, and understanding its axonal composition is critical to prevent muscle weakness during nerve blocks. We conducted a histological analysis on six cadaveric nerve specimens (four males and two females; mean age at death, 81.3 years old). The axonal composition of the main trunk of the CFN, the deep and superficial fibular nerves (DFN and SFN), and the Arb was verified through double immunofluorescence labeling with antibodies against neurofilament 200 and choline acetyltransferase. We revealed that the DFN contains motor and sensory fascicles that serve the anterior muscular compartment of the leg, including the fibularis longus and the first web space of the foot. Moreover, we showed that the SFN includes a major sensory branch innervating the skin of the lateral leg and the dorsum of the foot and a minor motor branch for the lateral muscular compartment of the leg. Furthermore, we demonstrated that the Abr contains a major sensory branch that targets the infrapatellar fat pad, the knee joint, and a minor motor branch innervating the superior part of the anterior muscular compartment of the leg. Thus, our study proves that the Arb is a motor-sensory mixed nerve, suggesting that an Arb block may significantly weaken the anterior leg muscles.