A new study by University of Rochester Medical Centre suggests that pain is not a symptom of arthritis but it is a cause of the condition.

The study revealed that the pain signals originating in arthritic joints and the biochemical processing of those signals as they reach the spinal cord worsen and expand arthritis. Researchers also added that the nerve pathways carrying pain signals transfer inflammation from arthritic joints to the spine and back again, which causing disease at both ends. The two way “crosstalk” might enable joint arthritis to transmit inflammation into the spinal cord and brain, through the central nervous system.

“Until relatively recently, osteoarthritis was believed to be due solely to wear and tear, and inevitable part of aging,” said Stephanos Kyrkanides, an associate professor of Dentistry at the University of Rochester Medical Centre. Kyrkanides also added, “Our study provides the first solid proof that some of those changes are related to pain processing, and suggests the mechanisms behind the effect.”

There is a common ground between arthritis and dentistry: the jaw joint is a common site of arthritic pain. The researchers assessed the levels of a pro-inflammatory signaling chemical called interleukin 1-beta (IL-1ß). In this experiment the higher level of the chemical in a peripheral joint caused higher levels IL-1ß, which produced in the dorsal horns of the spinal cord. The spinal cord cells called astrocytes, which cause more arthritic symptoms in joints. 

Kyrkanides said, “Our study results confirm that joints can export inflammation in the form of higher IL-1ß along sensory nerve pathways to the spinal cord, and that higher IL-1ß inflammation in the spinal cord is sufficient in itself to create osteoarthritis in peripheral joints.”

The study is published in journal Arthritis and Rheumatism.