Anatomic and Ultrasonographic Evaluation of the Knee Sensory Innervation: A Cadaveric Study to Determine Anatomic Targets in the Treatment of Chronic Knee Pain.

BACKGROUND AND OBJECTIVES: Osteoarthrosis is a main cause of knee pain in the elderly. Pain associated with this condition is often refractory to conservative treatment. Total knee replacement may be the best option for severe pathologies; however, the occurrence of a chronic pain state after knee replacement has been well documented in the literature. The previous descriptions of the genicular nerves have been considered somewhat inaccurate. This innervation is complex and exhibits significant interindividual variability. A precise description of these nerves will increase our knowledge on different patterns and targets, to guide treatment and improve outcomes. The objective of this study was to determine sensory innervation patterns of the knee joint and correlate them with dynamic visualization via ultrasound imaging.
METHODS: Systematic cadaveric dissections were performed to determine different patterns of sensory innervation of the knee followed by ultrasonographic correlation. A short-axis ultrasound view of the nerves was used to inject India ink at several points along their course to facilitate the anatomic dissection and confirm their location among adjacent structures.
RESULTS: The visualized structures were the following: infrapatellar branch of the saphenous nerve, the branches to vastus medialis, intermedius, and lateralis muscles; obturator nerve; and lateral retinacular and recurrent peroneal nerves.
CONCLUSIONS: We conclude that reproducible correlations showing the sensory innervations for the knee are linked to muscular structures. However, high variability among individuals makes it difficult to predict their paths. Our systematic approach, using direct visualization via ultrasound, allows a more accurate placement of the needle for therapeutic purposes.