During the recent years, a few studies have shed new light on the innervation patterns of the human patellar tendon, but the
area of the loose paratendinous connective tissue dorsal to the proximal tendon proper has yet not been investigated. That
is a drawback, since this is the area targeted in promising treatment regimens of chronic painful patellar tendinosis, namely
sclerosing Polidocanol injection therapy, and a new surgical method conforming to ultrasound and color Doppler guided arthroscopic
shaving, directed at neovessels found in the region. The present study thus aimed at investigating the paratendinous area
dorsal to the proximal patellar tendon proper in seven patients being operated for tendinosis. Biopsies were collected through
the new arthroscopic technique, approaching the tendon from the dorsal side. Samples were investigated using immunohistochemistry
with antibodies delineating general (PGP 9.5), sensory (SP/CGRP), and sympathetic (TH/NPY) nerve patterns, and also antibodies
against α
1- and α
2A-adrenoreceptors. Both small and large blood vessels had a marked perivascular innervation (PGP 9.5). Surprisingly, this perivascular
innervation was found only to a very limited extent to correspond to sensory nerves, while there were marked immunoreactions
for sympathetic markers. Adrenoreceptor immunoreactions frequently occurred in blood vessel walls. In conclusion, this study
demonstrates, for the first time, the innervation patterns of the area dorsal to the patellar tendon in man. It shows that
the area investigated is under marked influence by the sympathetic nervous system. Thus, sympathetic effects are likely to
occur for blood vessels of the area, which is interesting since color Doppler has revealed that vessels of this area (“neovessels”)
display a pathologically high blood flow in tendinosis. The findings are discussed in relation to aspects of vascular regulation,
and to pain symptoms of tendinosis.
Keywords Tendinopathy - Jumper’s knee - Sympathetic innervation - Adrenoreceptors