The present study was designed to examine the distribution and type of dorsal root ganglion (DRG) cells innervating the medial and lateral collateral ligaments and patellar tendons of the rat knee joint.

We selectively injected neural tracers (FG and HRP) into both collateral ligaments and patellar tendons and then charaterized the distribution and type of DRG cells in section.

FG-labelled DRG cells, innervating the medial and lateral collateral ligaments, were located in L1-S3 (former) and L1-L5 (later). The HRP-labelled DRG cells innervating the medial and lateral collateral ligaments were smaller than 600 m2. FG-labelled DRG cells innervating the patellar tendons were found in L1 to S1. The HRP-labelled cells innervating the patellar tendons were variable in size (100 m2 to 3000 m²).

This study indicates that the DRG origins of sensory nerves in the collateral ligaments and the patellar tendon of the rat knee joint are different. The majority of DRG cells innervating the patellar tendons are proprioceptive and mechanoceptive sensory cells. This finding suggests that the patellar ligaments have more neurological functions than the collateral ligaments.