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Kevin A. Kirby, DPM

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Carmichael, CA
Kevin A. Kirby, DPM

We provide the most advanced podiatric care to our patients with an emphasis on the biomechanics of the foot and lower extremity.
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Dr. Kevin Kirby graduated from the California College of Podiatric Medicine in 1983 and completed his first year surgical residency at the Veteran’s Administration Hospital in Palo Alto, California. He spent his second post-graduate year doing the Fellowship in Podiatric Biomechanics at CCPM where he also earned his MS degree. Dr. Kirby has authored or co-authored 27 articles in peer-reviewed journals, has authored or co-authored five book chapters, and has authored five books on foot and lower extremity biomechanics and orthosis therapy, all five of which have been translated into Spanish language editions. He has invented the subtalar joint axis palpation technique, the anterior axial radiographic projection, the supination resistance test, the maximum pronation test and the medial heel skive and lateral heel skive orthosis techniques. He has also created and developed the Subtalar Joint Axis Location and Rotational Equilibrium Theory of Foot Function and has co-developed the Subtalar Joint Equilibrium and Tissue Stress Approach to Biomechanical Therapy of the Foot and Lower Extremity. He has lectured internationally on 33 separate occasions in China, Spain, Belgium, New Zealand, Australia, England, Dominican Republic and Canada over the past 23 years on foot and lower extremity biomechanics, foot orthoses, and sports medicine. He has also lectured extensively throughout the United States. Dr. Kirby is a member of the editorial advisory board for the Journal of the American Podiatric Medical Association and a manuscript reviewer for the Journal of Biomechanics, Journal of Foot and Ankle Surgery, Medicine and Science in Sport and Exercise, Journal of Foot and Ankle Research and Journal of Sports Sciences. He is currently an Adjunct Associate Professor in the Department of Applied Biomechanics at the California School of Podiatric Medicine and has a full time podiatric biomechanics and surgical practice in Sacramento, California.

02/22/2026

Reverse Morton's Extension on Foot Orthoses

A Reverse Morton's Extension (RME) is a forefoot extension added plantar to the 2nd, 3rd, 4th and 5th metatarsal heads of a foot orthosis, in effect, accommodating the first metatarsal. Any type of suitable non-compressible, flexible material may be used for a RME including korex, EVA (ethylene vinyl acetate), or adhesive felt.

In my clinical practice, I prefer korex for permanent RMEs and adhesive felt for temporary RMEs on foot orthoses. RMEs can range in thickness from 1-6 mm and generally end distally at the digital sulcus. RMEs start proximally either butted up against the distal edge of the orthosis plate or blended onto the distal 10-15 mm of the dorsal orthosis plate.

The RME can be a very useful orthosis modification in the treatment of multiple pathologies. Conditions that respond clinically to a reduction in ground reaction force (GRF) plantar to the 1st metatarso-phalangeal joint (MPJ) such as sesamoiditis, sesamoid stress reactions/fractures, sesamoid avascular necrosis, functional hallux limitus, and structural hallux limitus are effectively treated by RMEs.

RMEs may also be used to increase the subtalar joint (STJ) pronation moments acting on the foot for treatment of peroneal tendinopathy, chronic lateral ankle instability, lateral-dorsal midfoot pain or an over-supinated position of the foot during gait. The RME may be modified to be thicker laterally plantar to the 4th and 5th metatarsal heads and thinner medially plantar to the 2nd and 3rd metatarsal heads to increase the "valgus wedging effect" on the forefoot to increase the external STJ pronation moments further.

Patients with plantar fascial irritation from the medial longitudinal arch (MLA) of the foot orthosis may also benefit from the addition of an RME to their foot orthosis. By reducing the plantar loading forces on the first MPJ, the medial band of the plantar fascia will be under less tension force and will bowstring less forcefully into the dorsal aspect of the MLA portion of the orthosis plate which may help reduce orthosis irritation to the plantar fascia in many cases.

The RME is a valuable orthosis modification which I have frequently used on almost a daily basis in my podiatric practice over the past four decades. When used along with a well-designed foot orthosis, the RME can often mean the difference between clinical success and clinical failure of the foot orthosis for the injured patient.

02/22/2026

Center of Pressure and Propulsion During Running

I had a great question from Matteo Ghezzi recently which I wanted to comment on in detail:

"Hi Kevin, I have read that in running during the horizontal propulsion phase the centre of pressure moves forward under the forefoot, which puts the GRF a greater distance away from the ankle joint, and this maximises the moment about the ankle and the power production. Is it because although the external moment arm increases, having the centre of pressure further away maximises the mechanical advantage of the plantarflexors as rotation acts through the MTPJ?"

Yes, the center of pressure (CoP) does more forward on the plantar forefoot during the latter half of the support phase (i.e., that phase when the foot in on the ground) of running. This forward movement of the ground reaction force (GRF) vector on the forefoot will increase the dorsiflexion moment arm for GRF to cause an ankle joint dorsiflexion moment.

The question then becomes, what happens to the mechanical advantage of the ankle joint plantarflexors in overcoming this external ankle joint dorsiflexion moment from GRF during the propulsive phase of running?

The bottom line is that during the latter half of the support phase of running, both the CoP and GRF vector are moving anteriorly toward the toes which, of course, is the result of the center of mass (CoM) moving progressively forward over the foot and also the ankle joint plantarflexors (i.e.., gastrocnemius, soleus, deep flexors and peroneals) undergoing contractile activity. This ankle joint plantarflexor activity during the latter half of support phase is first "eccentric", decelerating ankle joint dorsiflexion, and then, as the heel lifts from the ground, is a "concentric" plantarflexor activity as the ankle joint plantarflexes.

The problem here in discussiong mechanical advantage for the ankle joint plantarflexors is that the magnitude of GRF acting on the plantar forefoot is rapidly diminishing from the time of the middle of the support phase, when the CoM of the runner is directly over the foot, to the time at the end of propulsion when the magnitude of GRF is quite minimal.

This means that, yes, the ankle joint plantarflexors will have increased mechanical advantage due to the GRF being more distal on the plantar forefoot, but the overall magnitude of ankle joint plantarflexion moment will also be rapidly diminishing during propulsion since the CoM is rising again away from the ground and as a result, the magnitude of the GRF vector is rapidly diminishing.

In other words, the mechanical advantage of the ankle joint plantarflexors during the latter half of the support phase of running and propulsion is certainly something to consider and understand, but needs to combined with the knowledge of the rapidly decreasing magnitude and direction of the GRF vector to comprehend the rotational power that the ankle joint plantarflexors are exerting during that phase of running gait.

02/21/2026

Biomechanical Effects of Metatarsal Pads

Metatarsal pads have been used for years as a method to relieve mechanically-based pain in the forefoot and to provide patients with extra mechanical support at the level of the plantar forefoot to improve foot comfort. Even though there is little high-quality research to substantiate their therapeutic effectiveness, metatarsal pads are used by many clinicians who treat mechanically-based foot pathologies to treat specific painful conditions of the forefoot.

I have been judiciously using metatarsal pads to treat many pathological conditions of the foot over the past four decades of private practice. I have found them to be clinically useful for the treatment of conditions that are caused by excessive plantar pressures on the forefoot, such as metatarsalgia, metatarso-phalangeal joint (MPJ) capsulitis and diabetic neuropathic ulcerations. I have also found them to be useful in the treatment of conditions caused by excessive intermetatarsal pressures, such as intermetatarsal neuroma or neuritis, and for the treatment of conditions caused by excessive bending moments acting on the metatarsals, such as metatarsal stress reaction or stress fractures.

Metatarsal pads are best considered as a mechanical method by which to specifically transfer ground reaction force (GRF) from one area to another area of the plantar foot. The increased thickness of the metatarsal pad will increase the magnitude of GRF acting specifically at the area of the plantar foot that is in contact with the metatarsal pad.

Since pressure is defined by the formula, pressure = force/surface area, the increase in GRF by the metatarsal pad will also cause a localized increase in plantar pressure within the defined area of the plantar foot that is in contact with the pad. This localized increase in plantar pressure is caused by the increased compression of the plantar soft tissue structures due to contact with the thicker contours of the metatarsal pad.

In general, the thicker the metatarsal pad, the greater will be the increase in plantar pressure, and the thinner the pad, the smaller will be the increase in pressure at the area of contact of the pad with the plantar foot. In addition, the thicker the metatarsal pad, the larger will be the reduction in magnitude of GRF in the areas of the plantar foot which surround the pad, and the thinner the pad, the smaller will be the reduction in magnitude of GRF in the areas of the plantar foot which surround the pad.

Metatarsal pads may be used as an isolated mechanical treatment within a shoe, may be adhered to the shoe insole or sockliner, or may be combined with the therapeutic mechanical effects of a foot orthosis. Soft metatarsal pads may be ordered to be placed onto the foot orthosis, or a rigid metatarsal raise may be ordered into the orthosis by sculpting the positive cast to create a metatarsal pad that is “built-in” to the orthosis. I also normally keep adhesive-backed compressed felt metatarsal pads and adhesive-backed foam metatarsal pads of small, medium and large sizes in the office to allow me to modify shoe insoles, over-the-counter orthoses or prescription foot orthoses so that I have the greatest potential to produce maximum therapeutic results for the patient.

Metatarsal pads are generally designed with a "tear-drop" shape, with its thickest point (i.e. apex) being offset toward the distal edge of the pad so that there is a shallower slope to the pad proximally and a steeper slope distally (see my illustration below). The specific area of placement of metatarsal pads on an insole or foot orthosis will depend on the intended mechanical purpose of the pad. In other words, metatarsal pad placement will depend on whether the metatarsal pad is intended to reduce specific areas of high plantar pressure, reduce intermetatarsal pressures or reduce the bending moments on the metatarsals.

For pathologies where it is desired to reduce the plantar pressure on painful or tender areas of the foot, such as in MPJ capsulitis or plantar plate injuries, the apex of the metatarsal pad should be placed just proximal to the area of maximum tenderness in the plantar foot. In this fashion, the GRF will be increased at the metatarsal neck where there are no symptoms and GRF will be reduced at the MPJ level, where the patient is painful.

For example, in MPJ capsulitis or plantar plate injuries of the MPJ, the metatarsal pad should be placed with the apex of the pad at the proximal third of the metatarsal head when placed inside the shoe without an orthosis. When the pad is used on the dorsal aspect of a foot orthosis, the pad should be placed so that the distal edge of the pad is approximately 15 mm distal to the anterior edge of the orthosis.

When the goal of using a metatarsal pad is to reduce the pressure within the soft tissues between the distal metatarsals, such as in intermetatarsal neuritis or neuromas, the apex of the metatarsal pad should be placed directly plantar to the area of maximum tenderness of the neuroma. However, to best reduce intermetatarsal pressures, the metatarsal pad should be positioned so that its apex is between the distal metatarsals, and not directly plantar to the affected metatarsal as in the case of the treatment of MPJ capsulitis. In addition, it is critical in the mechanical treatment of intermetatarsal neuritis or neuromas that the orthosis also be worn in shoes which have adequate bolume for the weightbearing forefoot (i.e., adequate width and depth of toebox of shoe).

Shoes with increased volume will prevent medial-lateral compression of the intermetatarsal soft tissue structures and will reduce compression irritation of the intermetatarsal nerve.
When the clinician wants to use a metatarsal pad to reduce the bending moments on the metatarsal shaft, such as in the case of a metatarsal stress reaction or stress fracture, the apex of the pad should go directly plantar to the location of maximum tenderness on the dorsal aspect of the metatarsal shaft (see my illustration below). The metatarsal pad can be used initially in a post-operative shoe or other rigid-soled shoe, such as a clog, to give the patient more comfort while healing from the injury.

Later on, a metatarsal pad may be incorporated into a foot orthosis to prevent the future development of a stress injury. By supporting the site of the metatarsal stress injury with a plantarly directed force from a metatarsal pad and foot orthosis, the bending moments within the metatarsal will be reduced since the metatarsal head is no longer the prime weightbearing area of the metatarsal. Since excessive bending moments are a known cause of metatarsal stress fractures, reducing bending moments will not only reduce the pain in the injured metatarsal but will also prevent recurrence of the metatarsal stress-injury.

[Reprinted with permission from: September 2007 Newsletter in Kirby KA: Foot and Lower Extremity Biomechanics III: Precision Intricast Newsletters, 2002-2008. Precision Intricast, Inc., Payson, AZ, 2009, pp. 167-168.]

02/19/2026

Prescribing Better Custom Foot Orthoses: Morton's Neuroma

Thomas George Morton, MD, was a civil war surgeon that was one of the first to describe the most common nerve pathology that occurs within the forefoot, Morton’s neuroma (Morton TG: A peculiar and painful affection of the fourth metatarsophalangeal articulation. Am J Med Sci, 71:37-45, 1876). Patients with Morton’s neuroma classically describe their discomfort as being a burning, tingling, aching or cramping sensation in the area between the third and fourth metatarsal heads which often radiates toward the distal aspects of the third and fourth digits. Patients often report the pain of Morton’s neuroma as becoming worse when wearing tight shoes or when walking for long distances.

Clinical examination for Morton’s neuroma often reveals a “clicking mass” that is evident with manual side-to-side compression of the metatarsal heads (i.e. positive Mulder’s sign). Frequently tenderness is present between the plantar aspects of the third and fourth metatarsal heads and there may also be a specific loss of sharp/dull sensation between the plantar aspects of the third digit and fourth digits. Care must be taken during examination to also palpate the plantar plate area of the surrounding metatarsal heads to rule out plantar plate tears or other pathologies of the plantar forefoot.

Patients with Morton’s neuroma often have a history of wearing fashionable dress style shoes for many years. Shoes that are too narrow for the foot will generate significant external compression loading forces on the medial and lateral forefoot which will also be transmitted as a compression force to the intermetatarsal nerves (see my illustration below). Since the intermetatarsal nerves lie plantar to the deep transverse intermetatarsal ligament, the nerve can also be compressed between the ground and the intermetatarsal ligament, especially in shoes with higher heel height (Miller SJ, Nakra A: Morton’s Neuroma. In: Banks AS, Downey MS, Martin DE, Miller SJ (eds): McGlamry’s Comprehensive Textbook of Foot and Ankle Surgery, Vol. 1, 3rd ed, Lippincott Williams & Wilkins, 2001, pp. 231-252.)

Therefore, it is likely that any shoe that compresses the medial and lateral forefoot from side-to-side or any shoe that has a higher heel height may be responsible, over time, for the development of a Morton’s neuroma. Another theory of why the third intermetatarsal nerve is the most common site for neuroma is that there may be more frontal plane motion between the third and fourth metatarsal heads since the third intermetatarsal space is the junction between the medial and lateral columns of the foot.

The clinician should spend a considerable amount of time discussing with patients about the types of shoes that they wear for work and leisure in order make certain that their shoe choices are not causing excessive forefoot compression forces and an exacerbation of neuroma symptoms. Initial treatment involves a change to roomier shoes, icing the plantar forefoot twenty minutes once to twice a day, oral non-steroidal anti-inflammatory medicines, metatarsal pads and cortisone injections.

My clinical experience has consistently demonstrated that many patients improve with my initial treatment plan for neuroma and that many patients may also require a custom foot orthosis (CFO) to avoid surgical treatment for the neuroma. Orthoses can be very helpful in treating Morton’s neuroma if they are designed with the specific goal of reducing the abnormal internal forces acting on the nerve within the third intermetatarsal space during weightbearing activities.

First of all, the clinician needs to pay very close attention to the function of the foot during gait. If the patient exhibits late midstance pronation, instead of the more normal slight supination of the foot during late midstance, then this abnormal pronation motion will cause an abnormal dorsiflexion of the medial column relative to the lateral column when ground reaction force (GRF) is at its maximum on the forefoot (see my illustration below).

Late midstance pronation is common in patients with Morton’s neuroma and a well-fitted CFO with a standard rearfoot post, minimal medial expansion to increase arch congruity and possibly a slight (e.g. 2 mm) medial heel skive will help reduce late midstance pronation.

Another orthosis modification that is commonly used to treat Morton’s neuroma is a soft metatarsal pad that is sandwiched between the orthosis plate and the topcover. The goal of using a metatarsal pad on a CFO, or by itself in a dress shoe, is to attempt to place sufficient force between the third and fourth metatarsal shafts so that these metatarsals will “spread away” from the neuroma. Unfortunately, patients may have a difficult time with application of the metatarsal pad since many feel that it is more of "an uncomfortable bump" inside their arch, rather than a valuable part of the orthosis designed to reduce the compression forces acting on their neuroma.

After hundreds of trial-and-error applications of metatarsal pads on orthoses over the last four decades of treating these patients, I have found that placing the metatarsal pad so that its leading edge is 15 mm anterior to the distal orthosis edge is the position that is most comfortable for the majority of patients. However, I still write in the “special instructions” section of the orthosis order form for the lab to leave the anterior half of the orthosis topcover unglued so that I can more easily move the metatarsal pad to another location on the orthosis if the patient reports that the metatarsal pad “feels that it is in the wrong place” under their foot.

Lastly, it is important that when designing the CFO for a patient with a Morton’s neuroma that the patient understands that any foot orthosis will tend to make their shoe fit tighter which may also tend to increase the internal compression forces acting on their painful neuroma and prevent the orthosis from performing properly. Therefore, patients are informed that unless more roomy shoes can be worn that allow the orthosis to fit their shoes without increasing shoe tightness, that foot orthoses are unlikely to reduce their pain.

For patients that do need to wear stylish dress shoes for their work, I often will make both a thin cobra style dress orthosis with metatarsal pad for their dress shoes and a thicker full length orthosis with metatarsal pad for their athletic shoes in order to allow them to benefit from the therapeutic effects of orthoses while at work and while participating in their leisure activities.

[Reprinted with permission from: Kirby KA: Foot and Lower Extremity Biomechanics IV: Precision Intricast Newsletters, 2009-2013. Precision Intricast, Inc., Payson, AZ, 2014. pp. 91-92.]

02/17/2026

Tissue Stress Theory: Are the Measurements Proposed by Root et al Important to Optimize Custom Foot Orthosis Design?

One of the lectures I have been giving over the past 12 years is titled "Tissue Stress Theory: Changing the Paradigm in Biomechanical Therapy for the Foot and Lower Extremity". This lecture is very important for those of you following along so I wanted to give you a history of my training and how Tissue Stress Theory has become the predominant theory for designing custom foot orthoses by orthotic experts around the world.

During my four years of podiatry school and one year of Biomechanics Fellowship at the California College of Podiatric Medicine (CCPM), I was exclusively taught and trained on podiatric biomechanics theories that were proposed by Dr. Merton Root and his colleagues. These theories, which I will collectively call here Subtalar Neutral Theory (SN Theory), was based on his assumption that the measurement of externally apparent foot and lower extremity anatomical values could allow one to best predict gait function, best predict foot and lower extremity injury patterns and best help design custom foot orthoses for the patient.

SN Theory proposed that it was very important to accurately determine subtalar joint (STJ) neutral position, and then use this STJ neutral position measurement to find the relaxed calcaneal stance position, neutral calcaneal stance position, "rearfoot deformity" (i.e. rearfoot varus, rearfoot valgus), and "forefoot deformity" (i.e. forefoot varus, forefoot valgus). In addition, other measurements that comprised the Root et al measurement system included the STJ range of motion, hip range of motion, malleolar torsion, first ray range of motion, ankle joint dorsiflexion with the knee extended and flexed and tibial varum/valgum deformity (see lecture slide below).

Then once these measurements were painstakingly taken, we were taught, using SN Theory, that the custom foot orthosis being prescribed for the patient, in 95% of cases, should be balanced with the heel vertical, should end at the metatarsal neck level and did not need to include any forefoot extensions or topcovers. This was the "state of the art" in podiatric biomechanics at CCPM by the time I had started my Biomechanics Fellowship at CCPM in July 1984.

Once I started my Biomechanics Fellowship, and started seeing my own patients, using the measurements I had learned based on SN Theory. I began to become increasingly more frustrated these "Root measurements" over time since they were not able to predict any foot and/or lower extremity pathologies that I was seeing in my patients.

For example, I would often have patients with unilateral foot and/or lower extremity pain and obvious differences in foot structure between the two feet, but have almost identical and symmetrical Root biomechanical measurements. This didn't make any sense to me from a biomechanics standpoint and left me quite disheartened as a clinician, scientist and researcher.

It was not until I started measuring STJ axis location, utilizing my STJ axis palpation method (Kirby KA: Methods for determination of positional variations in the subtalar joint axis. JAPMA, 77: 228-234, 1987) that I started to realize that I potentially had discovered a measurement to better predict and understand the abnormal forces causing the patient's foot and/or lower extremity injury.

Then, 34 years ago, in March 1992, I first wrote about the importance of "Thinking Like an Engineer", describing how it was more important to understand the internal stresses acting on and within the structures of the foot and lower extremity, than on the measurement of externally-apparent foot "deformity", as proposed by Root et al (Kirby KA: Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Payson, AZ, 1997, pp. 267-268). Finally, three years later, in 1995, Tom McPoil and Gary Hunt wrote their seminal paper describing the concept of "Tissue Stress Theory", which improved on my concept of "Thinking Like an Engineer", to describe how they believed foot orthoses and therapies should be designed for injured patients.

To summarize, Tissue Stress Theory is based on the concept that it is more important to first determine the anatomical structure which is injured in the patient's foot and lower extremity and determine the abnormal stresses which have caused the injury when a patient presents to us with a foot and/or lower extremity injury. Once the anatomical location of the injury and abnormal stresses which caused the injury have been determined, the next step in Tissue Stress Theory is to design a treatment program, possibly including custom foot orthoses, which is specifically designed to do the following:

1. Reduce the abnormal stresses on the injured structure.

2. Optimizes gait function.

3. Causes no new injuries to the foot and/or lower extremity.

In other words, it may not be necessary to measure the STJ neutral position, as proposed by Dr. Root and colleagues, in order to prescribe the best custom foot orthosis for patients with foot and/or lower extremity injuries. All that is truly needed by the podiatrist and/or foot health professional is a good understanding of foot and lower extremity anatomy, muscle and gait function, Newtoninan mechanics and foot orthosis design variables to be able to utilize Tissue Stress Theory to design the best foot orthoses for patients with mechanically-based foot and lower extremity injuries (Fuller EA, Kirby KA: Subtalar joint equilibrium and tissue stress approach to biomechanical therapy of the foot and lower extremity. In Albert SF, Curran SA (eds): Biomechanics of the Lower Extremity: Theory and Practice, Volume 1. Bipedmed, LLC, Denver, 2013, pp. 205-264).

https://www.researchgate.net/publication/281609432_Subtalar_joint_equilibrium_and_tissue_stress_approach_to_biomechanical_therapy_of_the_foot_and_lower_extremity

02/16/2026

Anatomy and Treatment of Juvenile Pes Planus Deformity with Foot Orthoses

The child with pes planus deformity (i.e. juvenile pes planus) will have many structural abnormalities that occur along with the flattened longitudinal arch contour of their foot. The first illustration below is of a 7 year-old boy with bilateral pes planus deformity that I treated successfully, eliminating all painful symptoms and improving his gait pattern, with custom foot orthoses a number of years ago. The other photos are of an 8 y/o female who had such severe flatfoot that her lateral forefoot was barely touching the floor during relaxed bipedal standing.

Children with pes planus deformity always have a subtalar joint (STJ) which is maximally pronated. In addition, the talus is adducted and plantarflexed excessively which causes the STJ axis spatial location to become very medially deviated compared to a child with a more normal medial longitudinal arch height. The first ray (i.e. first metatarsal and medial cuneiform) and whole medial column are also excessively dorsiflexed relative to the rearfoot.

As a result, the medial longitudinal arch height is very low in these feet. If the longitudinal arch is low enough, the arch may even contact the ground in more severe juvenile pes planus deformities.
The knowledgeable and experienced clinician should be able to "see" through the skin of the foot and know where each bone of the foot is positioned relative to each other, even without radiographs or other imaging studies. My illustration below shows how the experienced clinician should be able to mentally visualize the basic three-dimensional osseous structure of any of their patient's feet.

Note the STJ axis location passes through the dorsal neck of the talus and, in these feet, are medially deviated, or, in other words, is not positioned directly over the first metatarsal head as should normally occur. Also note the relatively flat longitudinal arch contour which, along the medial STJ axis location, will increase the STJ pronation moments from ground reaction force. These excessive STJ pronation moments will tend to make the child more likely to complain of pain and fatigue during extended weightbearing activities.

The clinician making custom foot orthoses for these children with symptomatic flatfoot should focus on increasing the STJ supination moments from their custom foot orthoses with orthosis techniques such as medial heel skives, deep heel cups, rearfoot posts, and congruent medial longitudinal arch shapes that don't allow the longitudinal arch of the orthosis to deform under weightbearing load. In addition, the medial longitudinal arch of the orthoses should be high enough to help supinate the foot and prevent excessive medial arch collapse, but should not be so high that it creates blisters or pain in the medial arch of the child's foot.

By using well-made custom foot orthoses, treatment of symptomatic flatfoot deformity in the child can consistently help relieve the child's symptoms, and also improve their walking and running gait pattern. In my opinion, and from what I have consistently seen clinically over the past 41 years of podiatric practice, effective custom foot orthoses are under-utilized in the treatment of symptomatic flatfoot deformity.

02/16/2026

Effects of Orthosis Reaction Force with Lateral Heel Skive in Patients with Laterally Deviated Subtalar Joint Axes

I developed the lateral heel skive technique in about 1992 after first developing the medial heel skive technique with the help of Paul Rasmussen, previous owner of Precision Intricast Orthosis Laboratory (Kirby KA: Foot and Lower Extremity Biomechanics III: Precision Intricast Newsletters, 2002-2008. Precision Intricast, Inc., Payson, AZ, 2009, pp. 161-162).

The medial heel skive technique is a varus-heel-cup orthosis technique which I first described 34 years ago (Kirby KA: The medial heel skive technique: improving pronation control in foot orthoses. JAPMA, 82: 177-188, 1992). The lateral heel skive technique, which basically is the exact opposite of the medial heel skive techqnie, is a valgus-heel-cup orthosis technique which allows a discrete amount of valgus-wedging to be produced within the heel cup of custom foot orthoses. This valgus-wedged heel cup will shift ground reaction force (GRF) laterally at the orthosis heel cup which will increase the subtalar joint (STJ) pronation moment and/or decrease the STJ supination moment from the foot orthosis.
The lateral heel skive is very valuable in the treatment of laterally deviated STJ axes (see my illustration below).

Feet with laterally deviated STJ axes tend to suffer from symptoms related to excessive STJ supination moments such as peroneal tendinopathy, chronic inversion ankle sprains and lateral dorsal midfoot interosseous compression syndrome (i.e. lateral DMICS). The lateral heel skive technique is also helpful for patients with medial compartment osteoarthritis of the knee (Kirby KA: Foot and Lower Extremity Biomechanics III: Precision Intricast Newsletters, 2002-2008. Precision Intricast, Inc., Payson, AZ, 2009, pp. 163-164).

My illustration below of the foot standing on orthoses shows a typical vertically-balanced foot orthosis in a foot with a laterally deviated STJ axis on the left. The distal leg and talus are modelled as one structure, the talo-tibial unit, with the STJ axis attaching the talo-tibial unit to the calcaneus. Since the typical vertically-balanced orthosis is molded exactly to the plantar heel cup shape of the foot, then the medial calcaneal tubercle will be the area of the plantar calcaneus which receives the majority of reaction force from the orthosis.

On the right in the same illustration, is the same foot now standing on an orthosis with a 4 mm lateral heel skive modification added to it. Note how the valgus-wedged heel cup will shift orthosis reaction force more laterally which will, in turn, increase the STJ pronation moment arm from GRF acting on the plantar calcaneus which will, in turn, increase the STJ pronation moment acting at the heel cup area of the orthosis. The lateral heel skive is always combined with a flat rearfoot post in the orthosis to prevent inversion of orthosis shell on the ground and to better redirect GRF laterally on the plantar foot.

The lateral heel skive orthosis technique, in effect, tries to pronate the foot in order to accomplish the goal of reducing symptoms in patients that are related to increased STJ supination moment (i.e. peroneal tendinopathy, inversion ankle sprains, lateral DMICS) or that are related to increased medial loading of the knee joint (i.e. medial compartment osteoarthritis of knee). The lateral heel skive can be an extremely valuable orthosis modification for clinicians that specialize in the treatment of mechanically-based pathologies of the foot and lower extremity.

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5120 Manzanita Avenue, #100
Carmichael, CA
95608

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Monday	8:30am - 5pm
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Friday	8:30am - 5pm

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+19169258111

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http://www.kirbypodiatry.com/

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