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Heel Elevation In The Shoe: What The Literature Reveals
Are heel lifts actually detrimental for treating plantar fasciopathy? Does heel elevation have an impact on Achilles tendon loading in runners? Do high heels cause a medial shift of plantar pressures on the forefoot? In a thorough examination of the literature on heel elevation, this author discusses key biomechanical factors, compensatory effects and implications for treatment.
Inserting heel lifts into the footwear of patients has been a longstanding treatment intervention that podiatric physicians have practiced for decades. Whether treating limb length discrepancy, Achilles tendinopathy or plantar fasciopathy, practitioners have various perceptions about the efficacy of heel lift therapy and different interpretations of how these devices affect lower extremity function.
However, as I will demonstrate, despite the age-old tradition of prescribing heel elevation in footwear, a large volume of research conducted on this subject may cause the podiatric physician to reconsider when and how they implement this seemingly simple intervention.
There are several ways in which the human foot can be elevated under the heel in order to plantarflex the ankle. One method is simply to wear shoes with higher heels. Another method involves inserting heel lifts or wedges inside of the current footwear of the patient. Alternately, clinicians may apply heel lifts to foot orthoses that patients wear inside of the shoe. Researchers have studied each of these conditions and the results are somewhat surprising, if not contradictory to accepted beliefs of how patients respond to this simple treatment intervention.
What The Research Reveals About High Heel Shoes
There has been extensive study over the past 60 years on the effects of wearing shoes with elevated heels.1-3 These studies have evaluated the health risks of wearing fashionable footwear with higher heels but have also looked at gait changes, muscle activity and balance when people walk in high heel shoes. Evaluation of these studies provides insight into all interventions that elevate the heel of the human foot off the ground.
Wearing higher heeled shoes changes the way people walk. For example, kinematic studies reveal that elevated heel shoes cause shorter step length, lower step frequency and longer double support phase, and forefoot loading in comparison with barefoot walking.4-6 Some of these changes may reflect a lack of steadiness and balance when the foot is positioned in narrow, elevated heel footwear.
Hapsari and colleagues found that when footwear is elevated under the heel by 7 cm, functional stability was significantly compromised as measured by the Timed Up and Go test as well as functional reach testing.7 This is consistent with previous studies, which revealed a similar loss of functional stability in heel heights of only 4 cm.4 As a result, researchers have identified wearing high heeled shoes as a risk factor for suffering a traumatic fall.8-11 Loss of balance during standing and walking when wearing higher heel footwear can be the result of postural changes or changes in muscular activity, or both.
Compensation for wearing higher heels begins proximal in the body with anterior rotation of the pelvis and accentuation of lumbar lordosis.10,11 This increases compressive force on the low back, increasing activity of the erector spinae muscles to maintain balance, which may be the cause of low back pain patients commonly experience when wearing high heels.11,12
Researchers have observed the hip and knee to move into a varus position during gait with high heels.13 This varus joint moment at the hip causes increased muscular demand on the hip abductors when people wear elevated heel footwear.14 Higher external knee varus moments contribute to increased pressure on the medial knee compartment.15,16 Osteoarthritis of the knee most often arises in the medial compartment and is also associated with habitually wearing high heeled footwear.17,18
Barkema and coworkers studied 15 women walking over ground wearing footwear with three different heel heights of 1, 5 and 9 cm.19 They measured a systematic increase in external knee adduction (varus) moment corresponding with an increase in heel height. A similar systematic increase in external ankle inversion was evident as heel height increased. Barkema and coworkers measured a progressive inverted alignment of the rearfoot with increasing heel height, which would explain the delivery of a similar varus moment to the knee.19 All of these findings led the authors to conclude that high heel footwear could contribute to osteoarthritis of the medial knee compartment by causing varus forces at both the ankle and the knee.
Inverted positioning of the ankle and hindfoot from high heeled foowear can also contribute to ankle instability. Foster and coworkers studied 18 women walking in 1.5 cm (low heel) and 9.5 cm (high heel) shoes, and measured three dimensional kinematics and electromyography (EMG) activity in the lower extremity of the women.20 The women demonstrated a significant increase of peak ankle plantarflexion and inversion angles with the high heeled shoe. This appeared to evoke a compensatory increase in muscular activation of the peroneus longus in the women. In fact, Foster and coworkers measured twice the amount of peroneus longus activity in high heeled shoes in comparison to low heeled footwear. The findings led the authors to conclude that high heeled footwear postures the ankle and hindfoot into inversion, and predisposes people to an ankle sprain.
Some interesting changes in pressure occur on the plantar surface of the foot when people wear higher heeled footwear. As expected, studies show that high heel shoes shift pressure away from the rearfoot to the forefoot.12,21 However, what might be surprising to some is that, despite the supination effect of high heels on the rearfoot, plantar pressures on the forefoot shift medially on the forefoot, particularly to the first metatarsal with increasing heel height.22,23 In addition, the forefoot becomes less abducted with the wearing of high heel shoes.24,25 All of these findings are consistent with studies that show that higher heels pronate the forefoot, which is reciprocally coupled to supination of the rearfoot.26,27
High heeled shoes force the ankle into plantarflexion, which causes the knee to compensate with greater flexion.10,28 Flexion of the knee may be a compensation from the loss of shock absorption at the ankle.10 The combination of increased knee flexion with increased ankle flexion causes a significant loss of length and tension in the gastrocnemius muscle. Thus, the calf must work harder in high heels to provide power during gait.29 For reasons not fully understood, the medial gastrocnemius is more activated than the lateral with high heels, causing more medial calf pain.5,29 At the same time, electromyography studies show that activity of the tibialis anterior is unchanged between wearing low heel shoes in comparison with high heel shoes.13,20
What About Heel Rise Or Heel Drop In Athletic Shoes?
The measurement of elevation of the heel of a running shoe relative to the forefoot is known as heel-to-toe drop or, more commonly, “shoe drop.”30 Shoe drop is not the same as heel stack height, which measures the thickness of the midsole of the running shoe under the heel only but may not reflect the true heel-to-toe differential.31 There has been extensive study of the effects of shoe drop on running kinematics, kinetics and energy cost.32-34 These studies basically classify conventional running shoes as having a shoe drop of 10 to 12 mm while minimalist running shoes have a shoe drop of 0 to 8 mm.
In general, shoes with a shoe drop under 8 mm cause the runner to assume a forefoot strike with greater knee flexion at touchdown as well as experiencing greater ankle flexion during the stance phase.30,31,35 However, a randomized prospective study conducted by Malisoux and coworkers showed that the kinematic changes in those who wear minimalist (low shoe drop) footwear are likely due to the reduction of cushioning rather than reduction of heel height.36
Minimalist running shoes can have a low heel drop but a high heel stack. This type of shoe would have a thick midsole from heel to toe and very little difference in height between the two ends. Other minimalist shoes have very thin midsoles, low heel stack and low heel drop. Therefore, studies comparing minimalist shoes with conventional running shoes in terms of injury rates might obscure the true effects of shoe drop from the important effects of cushioning.37,38
In a randomized, prospective study looking at injuries in runners, Malisoux and coworkers assessed running shoes of similar heel stack height with different shoe drop height (10 mm, 6 mm and 0 mm).39 This Level I study showed that shoe drop did not affect the rate of injury in runners.
What Are The Effects Of Placing Heel Lifts Inside Shoes?
Podiatric physicians commonly place heel lifts inside the shoe to offset the negative effects of a tight calf muscle or Achilles tendon causing limited ankle joint dorsiflexion. The theory is that the human foot requires 10 degrees of dorsiflexion at the ankle joint during the midstance period of gait, which allows the tibia to advance over the foot while maintaining heel contact with the ground.40,41 When ankle joint dorsiflexion is limited, researchers speculate that a myriad of foot and ankle pathologies occur, including hallux abductovalgus, hammertoes, flatfoot, plantar fasciitis and Achilles tendinopathy.42-48
Gait changes due to limited ankle joint dorsiflexion include a shorter midstance period with early heel off as well as increased pronation of the subtalar and midtarsal joints.49-51 We would expect the application of heel lifts inside the shoe to minimize these negative kinematic effects of limited ankle joint dorsiflexion. Clinicians have implemented this treatment for decades without ever really knowing what the measured effects of this intervention would be.
It wasn’t until 2006 that Johanson and coworkers finally measured the effects of heel lifts on the kinematics of patients with limited (less than 5 degrees) ankle joint dorsiflexion.52 As expected, both 6 mm and 9 mm heel lifts increased ankle joint dorsiflexion range of motion during walking while delaying heel off in patients with ankle joint equinus. Although the results were significant from a statistical standpoint, the actual improvements are quite trivial from a clinical standpoint: a 9 mm lift will increase ankle joint dorsiflexion by only 1.23 degrees and increase the time to heel off by only 15 milliseconds.
In a follow-up study of patients with limited ankle joint dorsiflexion, Johanson and coworkers measured the EMG activity of lower leg muscles during the stance phase of gait.53 The study found significant increased activity of the medial gastrocnemius as well as the tibialis anterior in these patients, particularly between heel strike and heel off. The authors warned that clinicians treating Achilles tendinopathy with heel lifts should consider the potential negative effects of increased muscle activity in the gastrocnemius, which could actually increase strain in the injured tendon.
Johanson and coworkers speculated that increased tibialis anterior activity with heel lifts may have been due to increased eccentric loading of this muscle during the contact phase of gait.53 One would expect these same findings in EMG studies of people walking in high heeled shoes.13,20 However, Johanson and coworkers point out that those studies of high heeled shoes measured EMG activity during both stance and swing phase so eccentric loading could not be isolated.53
Wearing elevated heel shoes correlates with the presence of back pain.11 Yet interestingly, the application of heel lifts into standard shoes may decrease back pain in certain patients.54 Dananberg and Guiliano studied the effects of custom foot orthotics with heel lifts in treating patients with severe low back pain.54 They found a significant improvement after six months with functional scoring. Since the majority of the patients also demonstrated equinus deformity, the authors speculated that the heel lifts helped eliminate a sagittal plane blockade at the ankle joint, which would cause compensation proximally at the hip and low back.
Lee showed that 20 mm heel lifts would cause earlier activation of the lumbar erector spinae muscles.11 The study authors interpreted this as a positive effect in the treatment of low back pain. Barton and coworkers measured significant increased activity of the paraspinal muscles of the low back with the application of 20 mm heel lifts bilaterally into the shoes of 15 healthy people.55 They concluded that early activation and increased activity of the erector spinae muscles was a result of the heel lifts increasing proximal ground reaction force. This also occurs when people wear high heeled footwear. The authors also warned that while this increased muscle activity from heel elevation could be protective of the low back in some patients, others might experience an increase in pain due to changes in spinal alignment.
The notion of heel lifts increasing ground reaction forces was reinforced in a study conducted by Hessas and coworkers.56 The application of 20 mm heel lifts caused a 30 percent increase in plantar pressure under the metatarsals but also increased plantar pressure under the heel by over 50 percent. This dispels the notion of a heel lift reducing pressure under the calcaneus. At the same time, studies show that a shoe with an elevated heel will reduce pressure under the calcaneus.12,21 I will evaluate this further in the section below on plantar heel pain (see “Current Insights On Using Heel Elevation To Treat Plantar Heel Pain” ).
Does Heel Elevation Decrease Loading Of The Achilles Tendon?
Probably the most common use of heel lift therapy is for patients with Achilles tendinopathy. The rationale for this treatment is simple: elevating the heel will plantarflex the ankle, which will decrease strain on the Achilles.57 The reality is that this simple model is shortsighted in depicting all of the factors that affect the Achilles tendon in a patient during both quiet standing and gait.
When looking at studies of the effects of foowear and heel lifts on Achilles tendon loading, it becomes apparent that there are multiple variables to consider. Besides just looking at the overall magnitude of loading (peak loading), the rate of loading of the Achilles during walking and running might be more important. Also, the timing of peak loading during the walking or running gait cycle may have an effect on either damaging or potentially healing the Achilles tendon. Finally, a person will react to footwear and heel lifts with a neuromuscular response, which will change the magnitude of muscle firing of the gastrocnemius and/or soleus. These increases in muscle activity could outweigh any mechanical offloading of the Achilles brought on by these interventions.
To complicate this dilemma further, consider the study performed by Dixon and Kerwin, who studied the effects of heel lifts on Achilles tendon strain in three runners with different foot-strike styles in 1999.58 For both the rearfoot striker and the midfoot striker, the researchers found a significant increase in ankle joint moment and Achilles tendon forces when patients wore 7.5 mm and 15 mm heel lifts in comparison to the barefoot condition. For the forefoot striker, there was no significant effect of either heel lift. The authors repeated this study on seven other people, all of whom were rearfoot strikers.59 Among the patients, heel lifts did not reduce the magnitude of peak Achilles tendon force. However, the time to peak force or the rate of loading was lower for the entire group wearing heel lifts. At the same time, peak force and the rate of loading varied among individuals with some runners reacting favorably to the heel lifts while others had a negative response.
Other studies have shown that heel elevation of the shoe has no effect on peak tensile loading of the Achilles tendon during running.60,61 Yet many studies report improvement of symptoms when patients with Achilles tendinitis wear heel lifts.57,62,63 This may suggest that the rate of loading, rather than the total magnitude of loading, is more important in the treatment of Achilles injuries. Dixon and Kerwin showed that peak loading of the Achilles occurred later in the stance phase of running gait when patients used heel lifts, and they speculated that this demonstrated a slower rate of eccentric loading.59
Wearing and coworkers added more fuel to this controversy in a study of 12 recreational runners, comparing Achilles tendon acoustic velocity during walking barefoot to walking in shoes with a 10 mm heel elevation.64 Surprisingly, the shoe condition actually increased loading of the Achilles in comparison to the barefoot condition.
Wearing and colleagues considered other studies of muscle activation with higher heeled footwear as a possible explanation for these findings.13,28 Again, people appear to have increased calf muscle contraction when their heels are elevated. However, Wearing and coworkers also noted that with shoes, the patients in their study demonstrated significant gait changes in comparison to the barefoot condition, most notably with increased step length, decreased cadence and and higher ground reaction forces. All of these changes could have led to increased peak loading of the Achilles although the rate of loading was not different between the two conditions in this study.64
Wearing and coworkers followed their original study with another investigation in which they evaluated the effects of adding a 12 mm heel lift to a standard running shoe with a 10 mm shoe drop.65 While walking on a treadmill, the addition of the heel lift to the running shoe significantly reduced tensile load on the Achilles in comparison to the non-lift condition. The authors pointed out that the magnitude of load was reduced by the heel lift but this may not be a positive treatment effect as clinicians currently treat Achilles tendinopathy with interventions that actually increase eccentric loading of the tendon.
Farris and coworkers introduced a novel concept that patients treated for Achilles tendinopathy could optimally load their injured tendon by running while also using heel lifts to keep the loading in a therapeutic range.66 The authors measured Achilles tendon force with inverse dynamics and measured Achilles tendon strain via kinematics and ultrasound images. Ten women ran barefoot and then ran with 12 mm and 18 mm heel lifts. This study revealed that heel lifts reduce both the force and strain in the Achilles tendon during running. However, it was only the 18 mm heel lift that reduced the strain to the proper level to allow an adaptive response of the Achilles tendon to loading during running. The authors quote other studies noting patients can use running as an effective rehabilitation tool to increase collagen synthesis and tendon stiffness in the treatment of Achilles tendinopathy.67,68 Farris and coworkers propose that running with an 18 mm heel lift will effectively load the Achilles tendon for rehabilitation while not invoking harmful strain.66
Current Insights On Using Heel Elevation To Treat Plantar Heel Pain
Surprisingly, in comparison to the Achilles tendon, there are few published studies of heel lift therapy as a specific treatment for offloading the plantar fascia. A Cochrane Review of treatments for plantar heel pain does not even list heel lifts as a common intervention.69 Still, many clinicians use heel lifts or elevated heel shoes as part of an overall treatment intervention program.70,71
When we look at studies of methods to offload tensile strain in the plantar fascia, elevation of the heel can work via one of three strategies: decreasing deforming load from the Achilles, reducing pressure under the calcaneus and plantarflexing the metatarsals on the rearfoot.
Researchers have recognized the Achilles tendon as a primary deforming force that increases tensile strain on the plantar fascia.72 A cadaver study found the Achilles tendon load has about twice the straining effect on the plantar fascia as the body weight on the foot.73 Not surprisingly, researchers have identified patients with reduced ankle joint dorsiflexion due to contraction of the Achilles to be at greater risk to develop plantar heel pain.74,75 Accordingly, a recommendation of wearing higher heeled footwear has become a common treatment of plantar fasciitis.76,77
Employing a single subject finite foot and ankle model, Yu and colleagues studied the change in tension on the plantar fascia and the anterior talofibular ligament as the patient stood barefoot and then wore higher heeled shoes.78 Tension force in the anterior talofibular ligament increased significantly with increased heel height with the study authors noting a sixfold increase of strain with three-inch heels in comparison to being barefoot. Conversely, tension force in the plantar fascia decreased by 75 percent while standing in two-inch heels in comparison to being barefoot. Paradoxically, strain in the plantar fascia significantly increased in the three-inch heels to a level twofold greater than the barefoot condition. The authors provided no insight or explanation for this finding.
A study by Wibowo and coworkers demonstrates another therapeutic effect of elevated heel shoes to treat plantar heel pain.79 The authors measured a significant decrease in plantar pressure under the calcaneus as patients with calcaneal spurs wore shoes with progressively higher heels. Conversely, plantar pressure increased under the first metatarsal and hallux with higher heel shoes. Wibowo and colleagues noted that the patients in their study had significant reduction of plantar heel pain after wearing higher heel shoes for eight weeks, attaining optimal relief with 3 to 4 cm heel heights.79
Wibowo and colleagues also showed the pressure increased under the first metatarsal and hallux with increasing heel height, a finding that other studies of high heeled footwear have demonstrated.22,23 The kinematic changes that occur with higher heeled footwear verify supination of the rearfoot and pronation of the forefoot.26,27 Saraffian has noted this “twisted plate” orientation of the foot to theoretically decrease strain in the plantar aponeurosis.80
While elevated heel shoes will decrease pressure under the calcaneus, the insertion of heel lifts into a shoe will have the opposite effect. An investigation by Kogler and coworkers provided insight into the way heel lifts and shoes differ in their effects on loading the plantar fascia.81 They measured strain in the central band of the plantar fascia of 12 cadaver limbs, simulating static stance. Then the authors measured strain in the plantar fascia as the limb was positioned on heel lifts made of blocks of plastic or lifts that simulated the shank profile of a higher heel shoe. Only when the heel was elevated on a shank contoured lift, extending out under the midfoot and simulating the support of a high heel shoe, did strain in the plantar fascia decrease. When the heel of the cadaver specimen was elevated with a block-shaped lift placed only under the calcaneus, no significant change in plantar fascia strain occurred.
It is important to note that the Achilles tendon was not tensioned or loaded in the cadaver specimens in this study.81 Thus, the potential significant relief of strain in the plantar fascia by reducing load on the Achilles via the heel lift was not possible. However, this study is still important as it allows insight into the influence of heel wedges on the foot itself, void of any influence by the Achilles.
How The Shape Of The Heel Lift Can Affect The Foot
Kogler and colleagues suggested that the results of their study demonstrated that the heel elevation with an extended shank profile provided extended support of the foot under the calcaneus and the cuboid, which “shielded” or decreased loading of the medial arch or medial truss of the foot.81 Also, the extended support of the shank profile from the calcaneus to the midfoot may allow plantarflexion of the metatarsals, which shortens the length of the foot and decreases strain on the plantar fascia. However, Kogler and coworkers point out that effectiveness of a shoe to reduce strain in the plantar fascia depends on the conformity of the shank of the shoe to the shape of the foot to provide maximal contact. Kogler and colleagues observed that some patients had better reduction of plantar fascia strain than others in response to heel elevation, suggesting that the arch configuration of some people may predict better response to wearing high heel shoes for relief of plantar heel pain.81
This provides validity to the notion that combining a custom foot orthotic with heel lift therapy might be the better combination. Chia and coworkers performed pressure measurements in patients with plantar fasciitis and confirmed the findings of aforementioned studies that a simple heel lift by itself will increase plantar pressure under the calcaneus and forefoot.56,82 Prefabricated and custom foot orthoses decreased pressure in the heel and forefoot in the patients of this study. Studying four different types of inserts, Bonanno and coworkers also found that a heel lift by itself increased pressure under the heel and forefoot while reducing pressure in the midfoot, indicating decreased support of the arch.83
The studies by Chia and Bonanno and their respective coworkers illustrate that a heel lift by itself has detrimental effects for relieving plantar heel pain by increasing pressure on the calcaneus as well as reducing contact of the shoe or insole under the arch of the foot.82,83 Both studies show the benefit of contoured custom or prefabricated orthotics to offset these negative effects. These devices reduce pressure under the heel and forefoot while increasing pressure under the midfoot to increase arch support. Thus, when contemplating the use of heel lifts to offload the Achilles and plantar fascia, consider combining the heel lift with a contoured or custom foot orthosis. It is interesting that we have not seen laboratory or clinical trials that have studied this combination of foot orthotics with heel lifts other than the aforementioned study by Dananberg and Guiliano.54
In Conclusion
1. High heel shoes cause predictable gait changes that increase the risk of traumatic falls and inversion ankle sprains.
2. Heel lifts and higher heel shoes cause a neuromuscular response, which increases contractile activity of the calf musculature.
3. Heel lifts do not predictably reduce strain in the Achilles tendon but may reduce the rate of loading on this tendon. This response varies among individuals.
4. There are studies showing the positive effects of treating plantar heel pain with elevated heel shoes but virtually no studies showing any benefit of treating this condition with heel lifts alone.
5. A simple heel lift without extended contour under the midfoot may be detrimental to the treatment of plantar fasciopathy by increasing pressure under the calcaneus and reducing support of the shoe or insole under the arch of the foot.
6. Contoured prefabricated orthotics or custom orthotics can significantly reduce pressure under the heel and forefoot, and in combination with heel lifts might provide better treatment of plantar heel pain than heel lifts alone.
Dr. Richie is an Adjunct Associate Professor within the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt University in Oakland, Calif. He is a Fellow and Past President of the American Academy of Podiatric Sports Medicine. Dr. Richie is a Fellow of the American College of Foot and Ankle Surgeons. He is in private practice in Seal Beach, Calif.
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