![]() ![]() When these diseases are severe, mobility and functional limitations cause increased work loss, disability, nursing care, and premature retirement. The percentage cost of the US gross national product used to treat musculoskeletal disease has increased each decade since the 1960s. Over $86.2 billion is spent annually on rheumatic diseases. 10 Moreover, $118.5 billion per year was spent by US citizens on the care of musculoskeletal diseases. It is postulated that approximately nearly 1 in 5 adults of the US population is also demonstrating signs and symptoms of musculoskeletal disease. 9 In addition to clear-cut rheumatologic disease, there are more than 100 medical conditions that affect the muscles and tendons and joints that are classified as musculoskeletal related diseases. Adults over the age of 65 have more patient visits for these diseases than any other age group. As might be expected considering this high prevalence, the social and economic impact of rheumatic diseases taxes our healthcare systems. When this wear-and-tear process starts to affect more than one or two joints, this is described as a polyjoint arthritic disease process and it is more common in patients over the age of 50. With trauma and time, starting in the early 30s, the cartilaginous surfaces of the TMJ start to show wear-and-tear deterioration, which is then called osteoarthritis. In fact, multiple regression analysis demonstrated that age was, strongly, negatively correlated with the C6S concentration and the C6S:C4S ratio.Īrthralgia, arthritis, and arthrosis are among the most common conditions that affect the TMJ. The ratio of C6S to C4S was significantly lower in the group aged 60–70 years compared with the group aged 20–30 years. Their values were highest between 20 and 30 years of age, and thereafter they showed a tendency to decrease. They found that the concentrations of CS and HA varied with age. The subjects were 82 healthy volunteers ranging in age from 20 to 79 years. This was clearly demonstrated by a 2002 study 8 which examined normal synovial fluid and measured the concentrations of chondroitin 6-sulfate (C6S), chondroitin 4-sulfate (C4S), and hyaluronic acid (HA) in healthy subjects of different ages. These changes are considered one of the earliest signs of articular cartilage loss in osteoarthritis. These changes are partly caused by the decrease in water content that accompanies aging and a change in cartilage proteoglycan. This produces an increase in keratin sulfate and reduces chondroitin sulfate content in the synovial fluid. With aging, there is reduced accumulation of this synovial fluid and smaller proteoglycans are synthesized, which therefore hold less water and have less compressive ability, and there is more breakdown in the surface of the joint. In addition, the fluid that lubricates and protects the joint surface changes with age. In synovial joints, it has been reported that aging induces articular cartilage thinning and the cartilage actually has a color change (white to a dull yellow). With either excessive loading or loading without adequate lubrication there is a surface breakdown, leading to microfracture of the cartilage and osteoarthritis. Like all synovial joints, the fibrocartilage and TMJ disk are largely acellular and are maintained in health and repaired and lubricated by the synovial fluid in the joint. This fluid movement allows cartilage to undergo reversible deformations.ġ8.1.B Synovial Fluids and the Temporomandibular Joint It is recaptured as compression is removed. The twisted structure of this molecule is such that it creates space where water molecules can be bound inside this complex molecule, and compression of the cartilage releases this fluid. Aggregates of proteoglycans are linked to a core hyaluronic acid. 3–7 Proteoglycan molecules consist of a protein core with negatively charged glycoaminoglycan side chains composed of keratin sulfate and chondroitin sulfate. 1,2 Synovial fluid lubricates the joint, and loading of the articular fibrocartilage and subchondral bone causes chondrocytes in the articular cartilage to synthesize and secrete collagen and proteoglycans and other proteins necessary for cartilage and subchondral bone repair. This unique joint contains a disk composed of dense fibrous connective tissue, and the temporal and condylar articular surfaces are also covered with the fibrocartilage rather than the more typical hyaline cartilage seen in other joints. It is the only joint in the human body where the condyle slides completely out of its socket and yet is not considered dislocated. The temporomandibular joint (TMJ) is a complex synovial joint. Temporomandibular joint arthritis: implications, diagnosis, and management ![]()
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