Last updated: Mon, Jun 26, 2017
Three types of connective tissue are involved in joints; tendons, ligaments, and muscle fasciae.1 These three tissues are slightly different, but all use the proteins called collagens as their source of strength. Connective tissues have limited elasticity. For example, if ligaments are stretched by more than 4% of their length, they become semi-permanently stretched. In the best case, they may heal to their original length, but lose one-quarter to half of their strength. Stretched or inadequately strong ligaments cause their joint to be loose, leading to accelerated damage. This is the case when the ACL (anterior cruciate ligament) of the knee is torn, and may explain the frequent development of OA in such a knee. Connective tissue is subject to “repetitive microtrauma” if not sufficiently protected after an injury.
Both blood vessels and nerves grow into damaged and degenerated connective tissue, increasing their potential to generate nociceptive input to the nervous system. Biopsies from these areas have shown that pro-inflammatory chemicals are released in these areas.
Tissues that contain collagen are damaged by non-steroidal inflammatory drugs (NSAIDs), application of steroids, inactivity, or loss of innervation. All of these are currently-recommended and currently-performed treatments for various painful conditions of joints and their surrounding tissues.
Neuropeptides that sensitize nociceptors have been found within facet joints of the back and in and around the ligamentous joint that connects the sacrum on each side with the pelvis.