Heel Raise

Healthystep’s sagittal heel raises have been designed to enhance the anterior progression of body weight over the foot during late midstance while concurrently, reducing the foot- flattening dorsiflexion forces driven into the midfoot.

Thus, if ankle motion is limited for any soft tissue or articular reason, these heel lifts can help protect both the ankle and midfoot without detrimentally disturbing the foot’s rearfoot to midfoot alignment.

This design of heel raise is also useful for treating Achilles tendinopathies. It effectively enhances the action of the X-Line AT insole by reducing strains on the Achilles before heel lift.

Many commercial heel raises are built of one uniform thickness block of material added under the heel. The use of such lifts has been shown to alter ankle and foot motions, but they do not act in a way that restores normal function, even if used to compensate for a leg length difference. They cause the midfoot to plantarflex more during gait. This effectively creates an artificial midfoot or forefoot ‘equinus’ alignment across the foot and causes the toes to have to work in a more extended position. The effect is much the same as wearing a pair of higher-heeled shoes.

Our sagittal heel raises are not designed for balancing leg length discrepancies. Balancing leg length discrepancies is something that the research seems to indicate is unnecessary unless the discrepancy is large and/or acquired through trauma or surgery. This is because most terrain is uneven and feet and legs have an excellent capacity to accommodate natural differences by adjusting their functional lengths.

However, if you want to use a heel raise to increase the functional length of a limb, a sagittal raise will work without altering the natural foot posture as significantly as a block-type raise does. For leg length inequality, we suggest the whole foot should be raised, perhaps by using a single HealthyStep insole under one foot alone.

Sagittal heel raises are designed to reduce the range of ankle dorsiflexion necessary to allow body weight to safely transfer over the foot, correctly positioning it for acceleration during terminal stance. This, in turn, limits the dorsiflexion forces driven into the midfoot during
late stance.

In patients with limited ankle dorsiflexion motion, midfoot dorsiflexion forces and compensatory motions can risk injury and compromise locomotive efficiency.

The ankle joint acts as a pivot that moves body weight from behind the ankle at the start of a step, to position it in front of the stance foot before heel lift. The longer and faster the stride, the more ankle motion required. The more freely the ankle moves the less the midfoot is forced downwards (known as sagging deflection).

There is a close-coupled relationship between ankle dorsiflexion and amounts of foot profile depression (arch lowering or sagging deflection) during each step. This lowering is called midfoot dorsiflexion, or often foot pronation. The more the ankle joint dorsiflexes, the less the midfoot is obliged to lower through articular dorsiflexion to dissipate the forces generated by the body weight moving forward.

If ankle joint motion is restricted, more midfoot dorsiflexion and shock absorption are required because forward acceleration forces will increase on the midfoot as motion decreases in the ankle. Ankle motion should offer at least 10º of weight-bearing dorsiflexion and 15º of non-weightbearing dorsiflexion and 20 º of plantarflexion. Ankle motion should be sufficient and also well controlled by muscle strength, for calf muscles strength is just as important as their flexibility. The calf muscles should be powerful enough to achieve at least 10 repartitions of single-leg heel raises.

When ankle dorsiflexion motion is limited (commonly due to connective tissue tightening in response to muscle weakness or physiological changes to fascia), the midfoot has to compensate by creating more midfoot dorsiflexion. This risks damaging connective tissues and straining the plantar muscles, ligaments, and fascia that resist arch lowering. Excessive arch lowering is often referred to as hyper-pronation. The loss of safe and balanced biomechanics during ankle-midfoot coupled dorsiflexion can create injury, especially if foot muscles are weak and connective tissues are more fragile. This is more likely in individuals aged over 50 years, but the issue is most serious in neuropathic diabetics when it can result in a Charcot’s foot.

This image, from Clinical Biomechanics in Human Locomotion: Gait and Pathomechanical Principles, by A Horwood and N Chockalingam (2023), Academic Press, shows how soft tissue tensions under the foot are linked to the changes in tensions within the Achilles tendon as the ankle dorsiflexes. In particular, these are the spring ligament (1), the short plantar ligament (2), the long plantar ligament (3), and the plantar aponeurosis (PA) which is often known as the plantar fascia.

A well-designed orthosis can easily block the rate and even the amount of midfoot dorsiflexion straining the plantar soft tissues. This can be achieved by carefully supporting the plantar arch. However, in patients with limited ankle dorsiflexion, the midfoot’s motion might be an essential compensation. It should not be blocked by too high an arch support. An orthosis interfering with midfoot motion alone without assisting the loss of ankle dorsiflexion in late midstance, can feel uncomfortable across the arch and it may cause compensations elsewhere, which can risk injury.

The addition of a sagittal heel lift avoids such complications by lessening the requirement for ankle dorsiflexion to achieve adequate anterior body weight advancement before heel lift. Thus, ankle and midfoot stresses can be alleviated together. If ankle motion can be improved with rehabilitation over time, the sagittal lift can be removed later.