Common but not Normal
This edition of the C.W.G. Newsletter offers you a useful “three minute scan” to quickly and easily examine hyperpronation in clinics and offices where time is in short supply.
There are four elements in our scan, pes equinus, forefoot varus/supinatus, rearfoot pronation and midfoot pronation. These structural factors either create or reflect pronatory forces, so the greater the number and severity of each the more likely it will relate to the patient’s complaint and their tendency to develop problems in the future.
A more complex foot examination is necessary to design orthotics and prescribe specific footwear accurately, but our scan is perfect for developing an excellent sense of what is really happening to this complex organ.
Hyperpronation – The 3 Minute Office Scan
The foot is divided into three parts, the forefoot, midfoot and rearfoot . It is reasonable to describe any pronation in terms of where it occurs, i.e. midfoot and rearfoot pronation are accurate terms in that one does not always occur with the other.
The key element in hyperpronation is that the rearfoot and midfoot will usually pronate to “compensate” for a forefoot that is not level with the ground, in an effort to get all the metatarsal heads stable enough for pushoff. The forefoot always succeeds in getting flat to the ground, but the more it digresses from its neutral position (see fig.1), the more the midfoot and/or rearfoot must hypercompensate (i.e. hyperpronate) in order to do so.
When rearfoot pronation occurs, the entire weight bearing cycle starts and finishes medially, and there is no chance for the foot to become a rigid lever for pushoff. The forefoot will change shape in time (i.e. forefoot varus will increase with time (see fig. 5).
While most accept that rearfoot motion is likely a result of compensating for the forefoot, some accept that the rearfoot can have its own unique ability to pronate while others feel that all these factors are infinitely combinable and generally progressive.
Hyperpronation – The 3 Minute Office Scan (continued)
DEGREE OF PRONATION – The degree of pronation, is a matter of how far away the foot is from the ideal foot model, which is a subtalar (talo-calcaneal) joint that under full weight bearing is “neutral”, i.e. neither pronated nor supinated. The more unlevel the forefoot is with the ground the more the subtalar joint pronates to compensate. Forefoot varus and supinatus describe the angles of the forefoot to the ground that result in this hypercompensation.
At C.W.G. we class pronation generally as mild, moderate and severe with degrees in between classes, for example we use the term “very mild”, “moderately-severe” etc.. and apply these terms to the rearfoot and midfoot.
PES EQUINUS – This term applies to a soft tissue or osseous block to ankle dorsiflexion; imagine that someone shortened your achilles tendon by two inches and you would have a severe case of pes equinus.
Pes equinus of subtle degree probably represents the most common but least recognized source of hyperpronation today. Essentially, these patients cannot “heel down” during gait when their subtalar joints are in the neutral position, but like the rest of the human body if it can’t perform the way it is supposed to, it will usually find a way to do it, which in this case is to hyperpronate and push the knees together (valgus) in order to gain a few more degrees.
To test for pes equinus, ask your patient to stand in front of you and roll their feet outwards so the medial arch reappears. To check that your in neutral, the middle of the patella will be in line with the foot over the second or third toes (first toe for knees in severe knee valgus). Now ask your patient to squat down without letting the knees go out of position or the heels come off the ground (see fig. 3). How far can they go? Some patients will be surprisingly restricted. Now let them pronate and let their knees do what they want. You will likely see the knees drift medially into valgus as the feet relax and pronate to gain the ability to squat down a little further, and in a poor compensation for a mild case of pes equinus.
There are two basic choices in orthotic design for pes equinus. The ideal choice is to make the orthotic control abnormal pronation and put the patient in a shoe with the proper heel elevation. Failing to recognize the patient’s foot structure will result in improper shoe selection,the need to undercorrect the hyperpronation, or intolerance to orthotics.
The key point in pes equinus is that the foot must pronate to get the heel to the ground, and that proper control of abnormal pronation requires sufficient heel elevation so that the requirement to pronate is eliminated and the rest of the body can “get over” the foot during gait.
FOREFOOT VARUS AND SUPINATUS: These two terms are defined as a position of relative inversion of the forefoot on the rearfoot (see fig.5), with the primary difference being that forefoot varus is a fixed, osseous position while forefoot supinatus is flexible. The term forefoot varus has generally been used for years to describe both conditions. The ideal position of the forefoot is 0 degrees, or parallel to the ground even while weight bearing. As this angle of varus increases, the greater the force on the midfoot and rearfoot to pronate in order to get the forefoot to the ground. Once again the principle holds that normal joints will always try to make up for other joint abnormalities.
FINDING NEUTRAL AND MEASURING FOREFOOT VARUS: The fastest method of getting an idea of how much varus/supinatus your patient has is to ask them to stand in front of a chair and put one knee on its edge. Now put the foot in subtalar neutral by swinging the forefoot in and out (inversion/eversion) by holding the 4th and 5th met heads between your thumb and forefinger until the medial head of the talus has almost disappeared from under your thumb as in fig.4 (the head of the talus feels like a small bump which feels more prominent as you evert your fo
** The above information is not intended to replace a physicians advice. Seek a physicians advice first.
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