Study of the infrapatellar nerve.

During operations on the knee, such as open meniscectomy and pes anserinus transplant for chronic anteromedial rotatory instability of the knee, the infrapatellar nerve may easily be damaged or severed. Knowledge of the normal anatomical variations of this nerve is thus of importance to the surgeon, so that he can avoid postoperative distress caused by unintentional injury to the infrapatellar nerve. Anatomical variations of this nerve have been studied in 20 cadavers, with particular reference to its relationship to the sartorius and the nerve's distance from the medial femoral epicondyle. In 52.9% of the cadavers studied, the anatomy of the infrapatellar nerve was identical on both sides. Four types of nerve were found and classified according to their relationship to the sartorius: posterior, penetrating, parallel, and anterior. The commonest type was the posterior (62.2%), where the nerve emerged at the posterior border of the sartorius before passing superficial to it to supply the skin and fascia over the front and medial aspect of the knee and the proximal part of the leg. Situated furthest from the medial femoral epicondyle was the parallel type (average, 105.7 mm), which runs parallel to the posterior border of the sartorius before crossing it at infrapatellar level.