The sartorial branch of the saphenous nerve: its anatomy at the joint line of the knee.

PURPOSE: Injury to the saphenous nerve accounts for the majority of neurovascular complications during arthroscopic meniscal repairs. Although the anatomy of the infrapatellar branch has been studied, the location of the sartorial branch at the level of the joint line has not been defined adequately. The purpose of this study was to define the location of the sartorial branch in relation to surrounding structures at the level of the knee joint/meniscus.

TYPE OF STUDY: Cadaveric anatomic study and imaging study.

METHODS: We dissected 42 cadaveric knees and studied an additional 100 knees with axial magnetic resonance imaging (MRI). We measured distances from the nerve to adjacent structures and evaluated and graphically recorded 2-dimensional axial relationships. Dissections and MRIs were performed with the knee in full extension.

RESULTS: In the dissected cadaveric knees, the distance from the nerve to the anterior border of the sartorius averaged 16.0 mm, with 90% greater than 10.0 mm. The nerve was extrafascial at the joint line in only 43% of the specimens. Axial MRI examinations found the average distance to the anterior border of the sartorius to be 16.5 mm, with 82% greater than 1.0 cm. The average distance to the gracilis tendon was 9.4 mm; 91% were within 1.0 cm and 51% within 5 mm. The average distance to the semitendinosus was 14.9 mm; none was within 5 mm. The nerve was never posterior or lateral to the semitendinosus, never posterolateral or lateral to the gracilis, and was anterior to the sartorius in only 3% of knees.

CONCLUSIONS: This study describes the most common location of the sartorial branch of the saphenous nerve and the potential variability that may be encountered.

CLINICAL RELEVANCE: Understanding the anatomy of the sartorial branch at the level of the joint line and its relationships to surrounding structures will help to minimize the risk of injury to the nerve during common surgical procedures at the posteromedial corner of the knee.