And now, some light reading for a Saturday….
J Orthop Sports Phys Ther. 2001 Oct;31(10):567-7
What the Gait Guys say about this article:
Aren’t you glad you have mechanoreceptors?
As we have discussed in other posts, proprioception is subserved by cutaneous receptors in the skin (pacinian corpuscles, Ruffini endings, etc.), joint mechanoreceptors (types I,II,III and IV) and muscle spindles (nuclear bag and nuclear chain fibers) . It is both conscious and unconscious and travels in two main pathways in the nervous system.
Conscious proprioception (awareness of where a joint or body part is in space or action) arises from the peripheral mechanoreceptors in the skin and joints and travels in the dorsal column system (an ascending spinal cord information highway) to ultimately end in the thalamus of the brain, where the information is relayed to the cerebral cortex.
Unconscious proprioception arises from joint mechanoreceptors and muscle spindles and travels in the spino-cerebellar pathways to end in the midline vermis and flocculonodular lobes of the cerebellum.
Conscious proprioceptive information is relayed to other areas of the cortex and the cerebellum. Unconscious proprioceptive information is relayed from the cerebellum to the red nucleus to the thalamus and back to the cortex, to get integrated with the conscious proprioceptive information. This information is then sent down the spinal cord to effect a response in the periphery. As you can see, there is a constant feed back loop between the proprioceptors, the cerebellum and the cerebral cortex. This is what allow us to be balanced and coordinated in our movements and actions.
The ACL is blessed with type I, II and IV mechanoreceptors (Knee Surgery, Sports Traumatology, Arthroscopy Volume 9, Number 6) We remember that type I mechanoreceptors exist in the periphery of a joint capsule (or in this case, the periphery of the ACL) and are largely tonic in function (ie: they fire all the time) and type II are located deeper in the joint (or deeper in the ACL) and are largely phasic (ie they fire with movement). Type IV mechanoreceptors are largely pain receptors and anyone who has injured his knee can tell you all about them.
The article does a great job reviewing the importance of proprioception and how it relates to knee function and concludes “A higher physiological sensitivity to detecting a passive joint motion closer to full extension has been found both experimentally and clinically, which may protect the joint due to the close proximity to the limit of joint motion. Proprioception has been found to have a relation to subjective knee function, and patients with symptomatic ACL deficiency seem to have larger deficits than asymptomatic individuals.” Bottom line, never quit on the rehab and training of an ACL deficient knee until the absolute best outcome has unequivocally been achieved with certainty that no further improvement can be achieved…… absolute certainty. Too many stop shy of certainty, and your brain will know it. And it will show it in small gait, running and athletic skills.
Yup, this is some heavy stuff, but hey…you’re reading it, right? If we didn’t explain it in detail you might not believe that WE are The Gait Guys ……. more than just foot and shoe guys. After all, there is a brain attached to the other end calling the shots.
Sorting it out so you don’t have to…We remain…The Gait Guys