The L1 Nerve: Small Root, Big Consequences

Most practitioners know the thoracolumbar junction is important. Fewer understand why — specifically, what’s happening neurologically at L1 and what that means for every horse you’re putting your hands on.

L1 is the origin of the iliohypogastric nerve. That nerve runs from the spine, across the flank wall, and ends at the bottom of the abdomen. When it’s irritated — which it is in most horses with any degree of thoracolumbar compression — you get abdominal wall inhibition, flank hypersensitivity, and a horse that can’t recruit his core no matter how much rehab work you do. You’re not dealing with a weak horse. You’re dealing with a horse whose nerve supply to that musculature is compromised.