The nerve to vastus medialis as a target for treating chronic medial knee joint pain: an ultrasound-based anatomical localization study in healthy subjects

Abstract Background Chronic knee joint pain, resulting from osteoarthritis, post-surgical sequelae, or traumatic injuries, represents a debilitating clinical condition. Interventional approaches to manage chronic knee joint pain have been employed for decades, yielding variable outcomes in terms of pain relief, sustainability of analgesic effects, and functional restoration. The term “genicular nerves” is commonly used to refer to the primary sensory innervation of the knee joint capsule. However, recent studies have increasingly recognized the significance of additional neural structures, such as the nerve to vastus medialis. Methods This descriptive, prospective anatomical study involved 20 healthy volunteers. The nerve to vastus medialis was assessed using ultrasound. The following was documented: (a) confirmation of the presence of the nerve to vastus medialis; (b) number of branches/distribution patterns; (c) distance from the division of the NVM into its distal branches to the medial femoral epicondyle; and (d) positional relationship of the branches in the distal region of the knee. Results The presence of the nerve to vastus medialis was confirmed in all participants. The nerve exhibited considerable variability in terms of the number of branches (2 to 5). Two distinct types of branches were identified: (a) trans/intramuscular branches, which were present in varying numbers (0 to 3) in the proximal thigh likely providing motor innervation to the muscle; (b) extramuscular branches, (typically 2 or 3), located in the distal thigh, presumed to have a sensory function. The distance from the division of the NVM into its distal branches to the medial femoral epicondyle was 13.07 ± 3.40 cm. The depths of the distal branches ranged from 1.0 to 4.4 cm. Conclusion The findings from this study offer a standardized approach to the identification and mapping of the nerve to vastus medialis distal branches, essential for interventional treatments.