As the saying goes, ``Sprains become a habit.'' Ankle sprains (ankle sprains) are a disease that is easy to repeat once injured. CAI refers to a condition in which the sensation and motor function of the ankle decreases after an ankle sprain injury, resulting in repeated sprains, but until now it was not clear why CAI occurs.

　Therefore, the research group examined the cause of CAI using mice with foot instability (ankle wobbling) similar to that seen after a sprain.

　As a result, they discovered that in mice with foot instability, the sensory receptors (mechanoreceptors) in the ankle ligaments that detect ankle movement become misshapen. The number of mechanoreceptors was also reduced, resulting in decreased sensory and motor function in the ankle.

　Not only that, but they also found that the expression of PIEZO2, which plays an important role in nerve transmission, was decreased in sensory nerves that form mechanoreceptors, leading to a decrease in the ability to sense ankle motion.

　From the above, it has become clear that the instability of the foot that occurs after an ankle sprain leads to the degeneration of mechanoreceptors, leading to the development of CAI (decreased ankle sensation and motor function).

　In CAI, mechanoreceptors have already degenerated, so conventional rehabilitation has no beneficial effect. Rather, suppressing foot instability, which causes CAI, after a sprain is expected to be a rehabilitation method to prevent the onset of CAI. In the future, the company plans to advance the development of new treatments and rehabilitation to prevent the onset of CAI.

Paper information:[The American Journal of Sports Medicine] Chronic Ankle Joint Instability Induces Ankle Sensorimotor Dysfunction: A Controlled Laboratory Study