KNEEBAR

The kneebar is the joint lock attacking the knee by hyperextending the leg with the attacker's hips as the fulcrum. The mechanics are structurally identical to the armbar — both limbs are extended against the natural range of motion of the hinge joint, with the body of the attacker providing the lever — but the leg's larger muscles and shorter range mean the kneebar finishes faster and with less margin for error than the armbar.

From single-leg X or any ashi garami position, the attacker traps the opponent's leg between their own with the figure-four configuration, slides the captured leg's knee against their own pelvis as the fulcrum, and extends the hips forward to drive the knee past straight. The opponent's femur and tibia are held in alignment by the figure-four lock, which means there is no joint slack to absorb the hyperextension — every degree of attacker's hip extension translates directly into knee strain.

The kneebar is one of the more accessible leg locks in the modern competitive landscape because it does not require the inside heel hook's specific angles to finish. Anyone with a clean entry to ashi garami can attack the kneebar; the inside heel hook requires the inside sankaku position and the heel exposure that not every grip configuration produces. For this reason the kneebar remains a top-five submission in modern no-gi competition and is permitted in IBJJF nogi at brown belt and above.

Defensively the kneebar is escaped by stuffing the captured-leg foot toward the floor (which removes the figure-four\'s alignment), by spinning to the back of the attacker before the lock closes, or by tap-to-grip when the lock has already engaged. Like all leg locks, the kneebar produces damage before pain when the angle is correct, so the modern competition convention is to tap to the grip rather than test the joint.