The rearfoot is where the rubber hits the road, so to speak, in the gait cycle. Yes, as the foot swings foward, just before the heel hits the ground, there can be and usually are forces that going to help determine the position with which the heel actually strikes the ground. Anatomical variants all the way up to the back can adversely affect what is known as heel strike.
An older individual with an arthritic hip, because of the pain that occurs as the leg swings forward, in the hip joint, can force the heel to hit the ground in an abnormal manner.
A younger person with scoliosis for example, can also not have a normal heel contact because of the relative positioning of one leg versus the other.
The conditions that can cause an abnormal heel strike do not have to be as dramatic as these two examples. Minor deviations repeated over and over, hundreds if not thousands of times during the course of the day can end up creating issues within the foot as it functions through the gait cycle.
But once the heel hits the ground in whatever fashion, that sets the stage for how the rest of the foot will react as it attempts to move the body forward.
One of the things a good orthotic can do is improve the way the heel hits the ground and by doing so have a positive impact on the function of the foot.
Not all foot and ankle conditions require a change in the angle with which the heel hits the ground but if you are suffering from one such condition then more than likely you will require a prescription orthotic because store bought arch supports and even medical grade off the shelf orthotics really do not offer this feature. I should state that there are now medical grade off the shelf orthotics being made that advertise the ability to post them, but the couple I have seen have left me underwhelmed.
Heel strike can be controlled by a good orthotic in a few ways. One is what is known as posterior posting where there is an addition added to the bottom back of the orthotic that changes the angle with which the heel hits the ground. This post then forces the rearfoot into a different position than the patient is now walking normally. Many biomechanically related foot, ankle and leg issues are addressed with posterior posting.
Oher times the heel of the orthotic is "deep seated" meaning the heel portion of the orthotic is crater-like which then attempts to hold the heel in a certain position so the foot may function properly.
A good orthotic will also help cushion the impact of heel strike and disperse the force of the heel hitting the ground. Certain foot types, primarily rigid high arched feet are very poor shock absorbers and a good orthotic can help alleviate that problem.
Lastly, many individuals have what is known as a limb length discrepency meaning one leg is longer than the other. This can be due to an actual difference in the length of the limbs or it can be a "relative" difference from a condition like scoliosis which tilts the pelvis and thus makes the legs appear to be of a different length.
So by adding a heel lift to one of the orthotics we can compensate for the difference in limb length and allow the patient to walk in a more even gait.
Typically, the foot is broken into three sections, forefoot, midfoot and rearfoot. For the sake of this site the midfoot and rearfoot will be combined, as I am trying to just make a distinction between problems that occur on the ball of the foot (forefoot) and problems that occur in the rear of the foot and the various types of orthotics we can use to help in these situations.