proprioceptor

https://doi.org/10.1351/goldbook.12023
Sensory organ in a muscle, tendon or joint capsule that senses position or state of contraction.
Source:
PAC, 2015, 87, 841. (IUPAC Glossary of terms used in neurotoxicology (IUPAC Recommendations 2015)) on page 899 [Terms] [Paper]