The sagittal plane facilitation theory is a clinical theory or model of foot and lower limb biomechanics that is primarily concerned with facilitation motion in the sagittal plane as opposed to other models of foot biomechanics that are based on control and support of the foot. The model was first proposed and most clearly elucidated by Howard Dananberg, DPM.
The principle is that there needs to be adequate quality motion at the 3 rockers – heel contact of the calcaneus, the ankle joint and the first metatarsophalangeal joint. If motion at one or more of those rockers is inhibited in the sagittal plane during normal gait there will be compensations and those compensations may become pathological and cause symptoms. The inhibitors of the motion could be, for example, tight calf muscles limiting ankle motion or a functional hallux limitus interfering with motion at the first metatarsophalangeal joint.
If motion is limited or restricted at those rockers, then the body has to get the motion somewhere else if it is to move forward in sagittal place. The sagittal plane blocks in the ankle joint can be compensated for by getting that motion at the midtarsal or midfoot joints. This will result in those joints to “collapse” and can result in symptoms.
If the sagittal plane block is at the first metatarsophalangeal joint or is due to an inhibition of the the windlass mechanism, then this could result in a collapse of the mid-foot joints and the movement of the center of pressure laterally as the body attempts to get around that first metatarsophalangeal joint that just does not want to move or can not move.
The treatment of patients based on the sagittal plane model is to facilitation the motion at the rockers. For the ankle joint this might be placing the emphasis on stretching the calf muscle, heel raises and mobilization of the joints. For the first metatarsophalangeal joint, this might mean the use of the Kinetic wedge or the Cluffy Wedge for the functional hallux limitus or a rocker for a hallux rigidus.