Grade I: Short amplitude within the slack and back to complete relaxation
Grade II: Large amplitude, always back into complete relaxation. The maximal end-range is not achieved
Grade III: Large amplitude from midrange until the maximal end-range
Grade IV: Short amplitude always in or close to the end-range
Oftentimes, the literature describes a 5th grade as Thrust manipulation which is a quick thrust with a low amplitude at the end-range of movement.
Maitland describes grades I+II as techniques which don’t stretch the tissue with the goal of achieve pain reduction through proprioceptive input of the joint capsule.
The goal of grade III+IV on the other hand is often to mobilize the joint capsule through end-range stretch on the connective tissue.