Hilton's law, espoused by John Hilton in a series of medical lectures given in 1860–1862, is the observation that in the study of anatomy, the nerve supplying the muscles extending directly across and acting at a given joint also innervate the joint.
For example, the musculocutaneous nerve supplies the elbow joint of humans with pain and proprioception fibres. It also supplies coracobrachialis, biceps brachii, brachialis, and the forearm skin close to the insertion of each of those muscles. (The capsule and ligament receive an abundant sensory nerve supply. A sensory nerve supplying a joint also supplies the muscles moving the joint and the skin overlying the insertions of these muscles,a fact that has been codifies as HILTON'S JOINT.) Hilton's law arises as a result of the embryological development of humans (or indeed other animals). Hilton based his law upon his extensive anatomical knowledge and clinical experiences. As with most British surgeons of his day (1805–1878), he intensely studied anatomy.
Extensions of the law
Hilton's law is described above. Similar observations can be made, to extend the theory; often a nerve will supply both the muscles and skin relating to a particular joint. The observation often holds true in reverse - that is to say, a nerve that supplies skin or a muscle will often supply the applicable joint.