Proprioception is detected by the thousands of nerve endings we have in each limb or foot. Those nerve endings are communicating to the brain where that limb or foot is in space. The extreme in lost proprioception is in neurological injury like a slipped disk of the back. If you flip that dog’s foot onto it’s top, the dog won’t flip it back because he doesn’t know it’s in the wrong place – this is a surgical disease (knuckling in dogs). However, most changes in proprioceptive loss is more subtle – a dog whose knee joint is swollen from injury has stretched the nerve endings around the knee. When he walks he has less ability to move because there is less perception of where the knee is in relation to the rest of the limb. The old arthritic dog trying to cross the kitchen floor is so tense because she knows she has a decreased ability to catch herself if she falls due to decreased proprioception. An agility dog that is knocking bars, may have a subtle injury that has changed that tiny calculator between the foot and the brain of how high the bar is.