What is the topic of this review? Why proprioceptors, which are non-nociceptive, low-threshold mechanosensory neurons that monitor muscle contraction and body position, express several proton-sensing ion channels and receptors. What advances does it highlight? ASIC3 is a dual function protein for proton-sensing and mechano-sensing in proprioceptors that can be activated by eccentric muscle contraction or lactic acidosis. A role is proposed for proprioceptors in non-nociceptive unpleasantness (or sng), which is associated with their acid-sensing properties, in chronic musculoskeletal pain.