|
||||||||||||||||||||||||||||
|
II. Bioelectric phenomena in joint tissues.
The cells in dense connective tissues in animals respond to mechanical stress by making more tissue components. These tissue components are primarily outside the cells, such as collagen and the proteoglycans (large protein-polysaccharide complexes). The mechanism by which these cells become aware of use (mechanical stress) is not fully understood, but in each tissue there is clear evidence for a mechanical-electrical transduction constituting the signaling mechanism. Bone has been the most extensively studied, and knowledge of the response of bone to electric stimuli led to the development of the device which generates PEMF as an aid to bone healing (the bone growth stimulator). The specific mechanism by which the mechanical stimuli are changed to electrical signals has been extensively studied and shown to be based on fluid movement in the bone, causing charged ions to flow past tissue components which are stationary and carry electric charges (fixed charge groups). This phenomenon, called streaming potentials, also occurs in cartilage where compression causes the very high water content of the extracellular matrix to flow, carrying the positively charged sodium ions with it, leaving unneutralized negatively charged groups on the proteoglycans. Streaming potentials are important in signaling the chondrocytes, and also occur in other dense connective tissues such as tendon. This signaling mechanism can be imitated by the induced currents caused by PEMF in these tissues, as in bone.
III. Postulates:
A. Consideration of the causes of symptoms in osteoarthritis. The causes of pain in patients with osteoarthritis are vague, controversial and undoubtedly multiple. The articular cartilage is the site of the most important, fundamental pathology, but not the symptoms since there are no nerve endings in articular cartilage. The bone, especially the periosteum covering the bone, is especially rich in pain receptors and much of the pain arises from that tissue. The capsule of the joint, which is dense collagenous tissue, is also rich in nerve endings and another site of pain detection. The lining of the joint, the synovium, is another site of some of the pain and a primary source of the production of prostaglanding, which sensitize nociceptive (pain-detecting) nerve endings. Processes which put stress on the bone near the joint of the joint capsule, or cause microfractures of the bone plates under the joint surface (the trabeculae) or cause inflammation of the synovial membrane, all can contribute to the pain in these patients. In addition, outgrowths of bone and cartilage at the joint margins (especially where the capsule inserts into the junction of the articular cartilage and the bone) called osteophytes, are a site of pain during the period in which these outgrowths are forming. After the osteophytes are fully grown and apparent on x-ray, pain from this source may stop.
|
|||||||||||||||||||||||||||
