Anatomy – Concave Convex Law

Concave-Convex Law

A law of joint kinematics that states that if a convex joint surface moves on a stationary concave surface, the convex joint will slide in the direction opposite that of the angular motion of the bone, and that if a concave joint surface moves on a stationary convex surface, the articular surface will slide in the same direction as the angular motion of the bone.

Working with Concave-Convex Law in the pelvis and femur, we can help create stability and a foundation to open the hip. This protects the knee and ankle from too much rotation. Understand that one bone is always ‘fixated’ and one bone is in motion, so you focus on the bone in motion.

The convex-concave rule is the basis for determining the direction of the mobilizing force when joint mobilization gliding techniques are used to increase a certain joint motion. The direction in which sliding occurs depends on whether the moving surface is concave or convex.

Concave = hollowed or rounded inward
Convex = curved or rounded outward

If the moving joint surface is CONVEX, sliding is in the OPPOSITE direction of the angular movement of the bone.
If the moving joint surface is CONCAVE, sliding is in the SAME direction as the angular movement of the bone.