Effect of cutting the plantar fascia on mechanical properties of the foot

Regional differences in the mechanical properties of the plantar aponeurosis

The plantar aponeurosis functions to support the foot arch during weight bearing. Accurate anatomy and material properties are critical in developing analytical and computational models of this tissue. We determined the cross-sectional areas and material properties of four regions of the plantar aponeurosis: the proximal middle and distal middle portions of the tissue and the medial (to the first ray) and lateral (to the fifth ray) regions. Bone-plantar aponeurosis-bone specimens were harvested from fifteen cadaveric feet. Cross-sectional areas were measured using molding, casting, and sectioning methods. Mechanical testing was performed using displacement control triangle waves (0.5, 1, 2, 5, and 10 Hz) loaded to physiologic tension by estimating from body weight and area ratio of the region. Five specimens were tested for each region. Regional deformations were recorded by a high-speed video camera. There were overall differences in cross-sectional areas and biomechanical behavior across regions. The stress-strain responses are non-linear and mainly elastic (energy loss 3.6% to 7.2%). Moduli at the proximal middle and distal middle regions (400 and 522 MPa) were significantly higher than the medial and lateral regions (225 and 242 MPa). The effect of frequency on biomechanical outcomes was small (e.g., 3.5% change in modulus), except for energy loss (107% increase as frequency increased from 0.5 to 10 Hz). These results indicate that the plantar aponeurosis tensile response is non-linear, nearly elastic, and frequency independent. The cross-sectional area and material properties differ by region, and we suggest that such differences be included to accurately model this structure.

Plantar fasciitis and its relationship with hallux limitus

BACKGROUND

We sought to determine whether patients with plantar fasciitis have limited dorsiflexion in the first metatarsophalangeal joint and which type of foot, pronated or supinated, is most frequently associated with plantar fasciitis.

METHODS

The 100 study participants (34 men and 66 women) were divided into two groups: patients with plantar fasciitis and controls. The Foot Posture Index and dorsiflexion of the first metatarsophalangeal joint were compared between the two groups, and a correlation analysis was conducted to study their relationship.

RESULTS

In the plantar fasciitis group there was a slight limitation of dorsiflexion of the hallux that was not present in the control group (P < .001). Hallux dorsiflexion and the Foot Posture Index were inversely correlated (Spearman correlation coefficient, -0.441; P < .01).

CONCLUSIONS

Participants with plantar fasciitis presented less hallux dorsiflexion than those in the control group, and their most common foot type was the pronated foot.

Anatomy and biomechanical properties of the plantar aponeurosis: a cadaveric study

Objectives

To explore the anatomy of the plantar aponeurosis (PA) and its biomechanical effects on the first metatarsophalangeal (MTP) joint and foot arch.

Methods

Anatomic parameters (length, width and thickness of each central PA bundle and the main body of the central part) were measured in 8 cadaveric specimens. The ratios of the length and width of each bundle to the length and width of the central part were used to describe these bundles. Six cadaveric specimens were used to measure the range of motion of the first MTP joint before and after releasing the first bundle of the PA. Another 6 specimens were used to evaluate simulated static weight-bearing. Changes in foot arch height and plantar pressure were measured before and after dividing the first bundle.

Results

The average width and thickness of the origin of the central part at the calcaneal tubercle were 15.45 mm and 2.79 mm respectively. The ratio of the length of each bundle to the length of the central part was (from medial to lateral) 0.29, 0.30, 0.28, 0.25, and 0.27, respectively. Similarly, the ratio of the widths was 0.26, 0.25, 0.23, 0.19 and 0.17. The thickness of each bundle at the bifurcation of the PA into bundles was (from medial to lateral) 1.26 mm, 1.04 mm, 0.91 mm, 0.84 mm and 0.72 mm. The average dorsiflexion of the first MTP joint increased 10.16° after the first bundle was divided. Marked acute changes in the foot arch height and the plantar pressure were not observed after division.

Conclusions

The first PA bundle was not the longest, widest, or the thickest bundle. Releasing the first bundle increased the range of motion of the first MTP joint, but did not acutely change foot arch height or plantar pressure during static load testing.

Plantar fascia anatomy and its relationship with Achilles tendon and paratenon

Although the plantar fascia (PF) has been studied quite well from a biomechanical viewpoint, its microscopic properties have been overlooked: nothing is known about its content of elastic fibers, the features of the extracellular matrix or the extent of innervation. From a functional and clinical standpoint, the PF is often correlated with the triceps surae muscle, but the anatomical grounds for this link are not clear. The aim of this work was to focus on the PF macroscopic and microscopic properties and study how Achilles tendon diseases might affect it. Twelve feet from unembalmed human cadavers were dissected to isolate the PF. Specimens from each PF were tested with various histological and immunohistochemical stains. In a second stage, 52 magnetic resonance images (MRI) obtained from patients complaining of aspecific ankle or foot pain were analyzed, dividing the cases into two groups based on the presence or absence of signs of degeneration and/or inflammation of the Achilles tendon. The thickness of PF and paratenon was assessed in the two groups and statistical analyses were conducted. The PF is a tissue firmly joined to plantar muscles and skin. Analyzing its possible connections to the sural structures showed that this fascia is more closely connected to the paratenon of Achilles tendon than to the Achilles tendon, through the periosteum of the heel. The PF extended medially and laterally, continuing into the deep fasciae enveloping the abductor hallucis and abductor digiti minimi muscles, respectively. The PF was rich in hyaluronan, probably produced by fibroblastic-like cells described as 'fasciacytes'. Nerve endings and Pacini and Ruffini corpuscles were present, particularly in the medial and lateral portions, and on the surface of the muscles, suggesting a role for the PF in the proprioception of foot. In the radiological study, 27 of the 52 MRI showed signs of Achilles tendon inflammation and/or degeneration, and the PF was 3.43 ± 0.48 mm thick (99%CI and SD = 0.95), as opposed to 2.09 ± 0.24 mm (99%CI, SD = 0.47) in the patients in which the MRI revealed no Achilles tendon diseases; this difference in thickness of 1.29 ± 0.57 mm (99%CI) was statistically significant (P < 0.001). In the group of 27/52 patients with tendinopathies, the PF was more than 4.5 mm thick in 5, i.e. they exceeded the threshold for a diagnosis of plantar fasciitis. None of the other 25/52 paitents had a PF more than 4 mm thick. There was a statistically significant correlation between the thicknesses of the PF and the paratenon. These findings suggest that the plantar fascia has a role not only in supporting the longitudinal arch of the foot, but also in its proprioception and peripheral motor coordination. Its relationship with the paratenon of the Achilles tendon is consistent with the idea of triceps surae structures being involved in the PF pathology, so their rehabilitation can be considered appropriate. Finally, the high concentration of hyaluronan in the PF points to the feasibility of using hyaluronan injections in the fascia to treat plantar fasciitis.

Comparative Trial of the Foot Pressure Patterns between Corrective Orthotics, Formthotics, Bone Spur Pads and Flat Insoles in Patients with Chronic Plantar Fasciitis

Introduction: The objective of the study is to compare the efficacy of flat insoles, bone spur pads, pre-fabricated orthotics and customised orthotics in reducing plantar contact pressure of subjects with plantar fasciitis. Materials and Methods: This is a controlled non-blinded com- parative study conducted in a tertiary medical institute. Thirty subjects with unilateral plantar fasciitis between the ages of 20 and 65 years were recruited at the sports medicine clinic. The contact pressures and pressure distribution patterns in both feet for each subject were measured with sensor pressure mats while standing. Repeat measurements were made with the subjects wearing shoes, flat insoles, bone spur heel pads, pre-fabricated insoles and customised orthotics on both feet. The asymptomatic side was used as the control. Contact pressure measurements of the symptomatic and asymptomatic feet and power ratio of the pressure distribution pattern of the rearfoot were then compared. Results: Contact pressure was higher on the asymptomatic side due to unequal distribution of weight. Bone spur heel pads were ineffective in reducing rearfoot pressure while formthotics and customised orthotics reduced peak rearfoot pressures significantly. The power ratio of the rearfoot region decreased with the use of formthotics and customised orthotics. Conclusion: Pre-fabricated orthotics and customised orthotics reduced rearfoot peak forces on both sides while bone spurs heel pad increase rearfoot peak pressures. Pre-fabricated and customised orthotics are useful in distributing pressure uniformly over the rearfoot region. Key words: Biomechanics, Heel pain

Magnetic resonance imaging of stress injury of the cuneiform bones in patients with plantar fasciitis

OBJECTIVE

The authors reported the magnetic resonance (MR) appearance of stress fractures of the cuneiform bones in patients with plantar fasciitis and performed a review of the literature on stress fractures associated with plantar fasciitis.

MATERIALS AND METHODS

The authors performed a retrospective review of their experience with 5 cases of cuneiform stress fractures and associated plantar fasciitis. The medical records and MR examinations were reviewed. A literature search was performed on the PubMed search engine.

RESULTS

There were 5 patients (1 man and 4 women) with stress fractures of at least 1 cuneiform bone. Patients' age ranged from 41 to 77 years, and their average weight was 212 lb. All patients had heel pain and either midfoot or lateral foot pain. There were 2 intermediate, 1 medial, and 3 lateral cuneiform stress fractures seen on MR imaging in these 5 patients. Two of these patients had undergone plantar fasciotomy, and all 5 had been treated with steroid injections.

CONCLUSION

Plantar fascia injury, changes in gait, large body habitus, and excessive or new onset of exercise regimens are all potential causes of cuneiform stress fractures. Although the incidence of cuneiform stress fractures is extremely rare, they may occur in patients with plantar fasciitis.

A new minimally invasive technique for treating plantar fasciosis using bipolar radiofrequency: a prospective analysis

The purpose of this study was to evaluate the effectiveness of a new minimally invasive technique using bipolar radiofrequency in the treatment of plantar fasciosis. A prospective study was performed on 10 patients with recalcitrant plantar fasciosis that failed conservative care. A percutaneous microtenotomy was performed unilaterally with a Topaz microdebrider. Outcome measures included visual analog scale, American Orthopaedic Foot & Ankle Society (AOFAS) Hindfoot and Midfoot Scale, and patient satisfaction assessment. All patients had statistical improvement in outcome measures at 6 months and 1 year. One patient developed recurrent heel pain at the 1-year mark. There were no postoperative complications. This minimally invasive technique is a viable surgical treatment option in patients with plantar fasciosis that failed conservative care.

Diagnosis and management of the painful ankle/foot part 1: clinical anatomy and pathomechanics

Distinctive anatomical features can be witnessed in the ankle/foot complex, affording specific pathological conditions. Disorders of the ankle/foot complex are multifactoral and features in both the clinical anatomy and biomechanics contribute to the development of ankle/foot pain. The superior tibiofibular, distal tibiofibular, talocrural, subtalar, and midtarsal joint systems must all participate in function of the ankle/foot complex, as each biomechanically contributes to functional movements and clinical disorders witnessed in the lower extremity. A clinician's ability to effectively evaluate, diagnose, and treat the distal lower extremity is largely reliant upon a foundational understanding of the clinical anatomy and biomechanics of this complex complex. Thus, clinicians are encouraged to consider these distinctions when examining and diagnosing disorders of the ankle/foot.

Radiographic comparison of standing medial cuneiform arch height in adults with and without acquired flatfoot deformity

BACKGROUND

Adult acquired flatfoot (AAF) is characterized by decreased arch height, talar depression, medial arch depression and elongation, and forefoot abduction. We have measured standing arch height in AAF patients and in a control group of patients using the standing lateral medial cuneiform arch height radiographic measurement.

METHODS

Fifteen (25 feet) patients were selected with the clinical diagnosis of symptomatic AAF with no secondary diagnoses. A control group consisted of 36 (72 feet) patients with no foot deformities or prior foot surgeries. Arch height was measured in millimeters using the standing medial cuneiform height on the lateral radiographic view.

RESULTS

The mean standing medial cuneiform arch height in the control group was 18.38 mm. The mean arch height in the AAF group was 11.04 mm (p < 0.001). There were no differences between right and left feet in the control group or symptomatic and contralateral feet in the AAF group. Body mass index (BMI) in the control group was 26.17 and in the AAF 33.74. (p = 0.007).

CONCLUSION

These data provide a control value for the arch height using the medial cuneiform as reference. The decrease in arch height is a strong indicator of AAF. A study with larger numbers of patients is necessary.

Conservative Chiropractic Management of Recalcitrant Foot Pain After Fasciotomy: A Retrospective Case Review

OBJECTIVE

The objective of this study was to describe the safety and potential therapeutic benefit of joint mobilization and manipulation in the conservative management of patients with recalcitrant foot pain after plantar fasciotomy.

METHODS

The study design was a retrospective review of outcomes of 15 patients seen in a multidisciplinary office setting. All patients had undergone plantar fasciotomy within the 9 months before their admission and had developed lateral foot pain after operation. Each patient had exhibited suboptimal improvement with at least a 4- to 6-week trial of nonsteroidal anti-inflammatory drugs, shoe padding, and rest as prescribed by the attending podiatric surgeon. Manual therapy consisted of either grade III or grade IV joint mobilization and/or high-velocity, low-amplitude chiropractic manipulation to the affected joints in the foot and ankle, and home-based exercise. Outcome criteria were empirically defined as significant improvement, moderate improvement, or no change as assessed by each patient based on a verbal rating scale.

RESULTS

There was no long-lasting complication associated with any of the procedures, although a common pattern of transient pain migration over the dorsum of the foot into the ankle was noted in some patients; this resolved by the time of discharge. Of the patients with pain in the calcaneocuboid and/or fifth tarsometatarsal articulation, 11 noted significant improvement, 3 experienced moderate improvement, and 1 reported no change. Patients who complied with home care instructions responded better to therapy in most instances.

CONCLUSIONS

These preliminary findings suggest that joint mobilization and manipulation are safe conservative procedures to use in the treatment of patients with lateral column foot pain in status post plantar fasciotomy.

The Pathomechanics of Plantar Fasciitis

Plantar fasciitis is a musculoskeletal disorder primarily affecting the fascial enthesis. Although poorly understood, the development of plantar fasciitis is thought to have a mechanical origin. In particular, pes planus foot types and lower-limb biomechanics that result in a lowered medial longitudinal arch are thought to create excessive tensile strain within the fascia, producing microscopic tears and chronic inflammation. However, contrary to clinical doctrine, histological evidence does not support this concept, with inflammation rarely observed in chronic plantar fasciitis. Similarly, scientific support for the role of arch mechanics in the development of plantar fasciitis is equivocal, despite an abundance of anecdotal evidence indicating a causal link between arch function and heel pain. This may, in part, reflect the difficulty in measuring arch mechanics in vivo. However, it may also indicate that tensile failure is not a predominant feature in the pathomechanics of plantar fasciitis. Alternative mechanisms including 'stress-shielding', vascular and metabolic disturbances, the formation of free radicals, hyperthermia and genetic factors have also been linked to degenerative change in connective tissues. Further research is needed to ascertain the importance of such factors in the development of plantar fasciitis.

Diagnosis and Management of the Painful Ankle/Foot. Part 2: Examination, Interpretation, and Management

Diagnosis, interpretation, and subsequent management of ankle/foot pathology can be challenging to clinicians. A sensitive and specific physical examination is the strategy of choice for diagnosing selected ankle/foot injuries and additional diagnostic procedures, at considerable cost, may not provide additional information for clinical diagnosis and management. Because of a distal location in the sclerotome and the reduced convergence of afferent signals from this region to the dorsal horn of the spinal cord, pain reference patterns are low and the localization of symptoms is trustworthy. Effective management of the painful ankle/foot is closely linked to a tissue-specific clinical examination. The examination of the ankle/foot should include passive and resistive tests that provide information regarding movement limitations and pain provocation. Special tests can augment the findings from the examination, suggesting compromises in the structural and functional integrity of the ankle/foot complex. The weight bearing function of the ankle/foot compounds the clinician's diagnostic picture, as limits and pain provocation are frequently produced only when the patient attempts to function in weight bearing. As a consequence, clinicians should consider this feature by implementing numerous weightbearing components in the diagnosis and management of ankle/foot afflictions. Limits in passive motion can be classified as either capsular or non-capsular patterns. Conversely, patients can present with ankle/foot pain that demonstrates no limitation of motion. Bursitis, tendopathy, compression neuropathy, and instability can produce ankle/foot pain that is challenging to diagnose, especially when they are the consequence of functional weight bearing. Numerous non-surgical measures can be implemented in treating the painful ankle/foot, reserving surgical interventions for those patients who are resistant to conservative care.

Contribution of plantar fascia to the increased forefoot pressures in diabetic patients

OBJECTIVES

Secondary to peripheral neuropathy, plantar hyperpressure is a proven risk factor for foot ulceration. But limited joint mobility (LJM) and soft tissue abnormalities may also contribute. The aim of this study was to evaluate the relationships among thickness of plantar fascia, mobility of the metatarso-phalangeal joint, and forces expressed under the metatarsal heads.

RESEARCH DESIGN AND METHODS

We evaluated 61 diabetic patients: 27 without neuropathy (D group), 19 with neuropathy (DN group), and 15 with previous neuropathic foot ulceration (DNPU group). We also examined 21 control subjects (C). Ultrasound evaluation was performed with a high resolution 8- to 10-MHz linear array (Toshiba Tosbee SSA 240). The foot loading pattern was evaluated with a piezo-dynamometric platform. First metatarso-phalangeal joint mobility was assessed with a mechanic goniometer.

RESULTS

Diabetic patients presented increased thickness of plantar fascia (D 2.9 +/- 1.2 mm, DN 3.0 +/- 0.8 mm, DNPU 3.1 +/- 1.0 mm, and C 2.0 +/- 0.5.mm; P < 0.05), and significantly reduced motion range at the metatarso-phalangeal joint (D 54.0 +/- 29.4 degrees, DN 54.9 +/- 17.2 degrees, DNPU 46.8 +/- 20.7 degrees, and C 100.0 +/- 10.0 degrees; P < 0.05). The evaluation of foot-floor interaction under the metatarsal heads showed increased vertical forces in DN and DNPU and increased medio-lateral forces in DNPU. An inverse correlation was found between the thickness of plantar fascia and metatarso-phalangeal joint mobility (r = -0.53). The thickness of plantar fascia was directly correlated with vertical forces under the metatarsal heads (r = 0.52).

CONCLUSIONS

In diabetic patients, soft tissue involvement may contribute to the increase of vertical forces under the metatarsal heads. Changes in the structure of plantar fascia may also influence the mobility of the first metatarso-phalangeal joint.

Lateral column symptomatology following plantar fascial release: a prospective study

Plantar fasciitis or heel spur syndrome usually resolves with conservative management, but for patients with continued pain, surgical intervention is often pursued. In some cases, plantar fasciitis is relieved, but pain in the lateral column area appears postoperatively. This lateral column pain may be debilitating for the patient and often overlooked by the foot and ankle surgeon. The goal of the study was to identify the maximum amount of plantar fascia that can be surgically released to treat recalcitrant heel pain effectively while preventing the development of lateral column symptoms. All patients undergoing plantar fasciotomy after failing conservative treatment were eligible to participate. Patients rated their pain with an 11-point (0-10) visual analog scale (VAS) and described its location prior to and at monthly intervals after their surgery. Surgeons recorded whether 25, 50, or 66% of the plantar fascia was released during surgery. Open procedures were performed 72% of the time, and endoscopically in 28% of the patients. Key outcome variables included degree of fascial release and foot structure. Patients (n = 47) with lateral column pain after surgery (n = 15 feet) had a mean +/- S.E. of 60.6 +/- 3.0% of their plantar fascia released while those without pain (n = 35 feet) had only 48.7 +/- 1.9% of this fascia released during surgery (ANOVA, p = .019). Age, weight, body mass index, gender, smoking status, comorbidities, general health, surgical procedure, postoperative care, calcaneal inclination angle, and talar declination angle did not differ for these groups (p > .146). For this patient population, regardless of surgical technique (endoscopic or open release), lateral column symptoms were more likely to result when more than 50% of the plantar fascia was released. The report proposes that a maximum of 50% of the plantar fascia be released during surgery.

Computer-assisted assessment of lateral column movement following plantar fascial release: a cadaveric study

In patients who fail conservative treatment, releasing the plantar fascia relieves heel pain but destabilizes the lateral column of the foot. After surgery, pain can present in the area of the sinus tarsi, extensor digitorum brevis muscle, between the fourth and fifth metatarsals, and at the calcaneocuboid joint. The precise mechanism and involved structures for this painful compensation remains unclear. The authors hypothesized that the lateral plantar fascial band, bifurcate and cervical ligaments, lateral talocalcaneal ligament, and interosseous talocalcaneal ligament become excessively strained after this surgery. Using eight cadaver lower extremity limbs amputated 7 cm above the ankle joint, structural changes in the foot in response to staged release of the plantar fascia were measured. All ligament, tendon, and osseous structures were exposed along the plantar, medial, and lateral aspects of the foot and ankle. Using a servohydraulic system, compressive loads in increasing increments (50 lbs) were applied along the tibial axis. Tissue and bony structure displacement in the foot was measured using images electronically captured from two fixed cameras and a digital camera following each load change. All measurements were made in pixels and converted to millimeters in a spreadsheet program. Except for plantar fascial measurements, data were expressed as percentage of initial baseline. As expected, increasing compressive loads changed all measurements [repeated measures ANOVA, p<.04]. When releasing the plantar fascia, the inferior sinus tarsi space widened (intact, 85.4+/-10.8%; 1/4 release, 87.7+/-13.0; 1/2 release, 88.3+/-9.2; 3/4 release, 91.2+/-8.8; p<.04). Lateral length increased and medial height decreased, while medial length and lateral height were unchanged as the fascia was sequentially released. Significant movement of the inferior sinus tarsi strained the bifurcate and cervical ligaments, the lateral talocalcaneal ligament, and interosseous talocaneal ligament, which may account for pain following surgery. The initial 1/4 cut of the plantar fascia exerted the greatest mechanical alteration of the foot, suggesting that a partial release may relieve heel pain while optimizing the patient's chances of maintaining structural integrity with 75% of the plantar fascia intact.

Five-year follow-up results of instep plantar fasciotomy for chronic heel pain

The results of a 5-year follow-up of patients who underwent surgical partial release of plantar fascia with plantar skin incision for treatment of chronic heel pain are presented. Evaluation included survey results from both a modified Mayo Scoring System and a list of specific questions developed by the authors. Thirty-three feet of 30 patients are evaluated. Thirty of the 33 feet studied achieved good or excellent results, scoring 80 or better on a 100-point scale. Ninety percent pain relief was achieved in 27 of the 33 feet studied (81.8%). A satisfaction rate of 90% or better was found with 30 of the 33 feet studied (90.9%). Long-lasting complications were described by five patients, including opposite foot pain, dorsal foot pain after extended activity, scar tissue discomfort, callus at scar area, and continued heel pain.

Endoscopic release of plantar fasciitis--a benign procedure?

This is a case report of a patient suffering from subcalcaneal pain syndrome due to plantar fasciitis that was resistant to non surgical treatment. After endoscopic partial release of the plantar fascia the patient was pain free for several weeks, before he became symptomatic again. This new pain was located more proximally. An MRI study showed a stress reaction of the calcaneus.

Endoscopic plantar fascia release

An anatomic exploration showed that reliable landmarks could allow a safe division of the plantar fascia. The reference line was the posterior border of the medial malleolus, 1 cm from the plantar skin. A clinical study on 53 patients (65 feet) showed that, at follow-up of over 2 years, the procedure effectively relieved heel pain in 89% of patients, morning stiffness in 92%, and allowed 71% to return to unrestricted sports activity. There were 2 complications with lateral heel pain. Patients must be properly selected, and must have had the full range of conservative treatment. Symptoms should have been intractable for approximately 1 year. In this group, good results can be expected with minimum short-term morbidity.

Subtalar pronation--relationship to the medial longitudinal arch loading in the normal foot

A three-dimensional biomechanical model was used to calculate the mechanical response of the foot to a load of 683 Newtons with the subtalar joint in the neutral position, at five degrees of pronation, and at five degrees of supination. Pronation causes the forefoot to evert, increasing the load borne by the first metatarsal. This results in a 47% increase in the moment about the talonavicular joint and a 58% increase in the moment about the navicular-medial cuneiform joint. Subtalar joint supination causes the forefoot to invert and results in a 55% increase in the moment about the calcaneal-cuboid joint.

Effect of varying arch height with and without the plantar fascia on the mechanical properties of the foot

A biomechanical model was used to calculate the mechanical properties of the foot at a load of 683 newtons, while changing arch height with and without the plantar fascia. An increase in arch height from 20 mm to 60 mm decreased predicted vertical displacement of the foot from 11.8 mm to 5.5 mm with the plantar fascia intact and from 13.5 mm to 7.5 mm without the plantar fascia. The amount of horizontal elongation decreased from 8.6 mm to 8.4 mm with the plantar fascia and increased from 9.8 mm to 11.7 mm without. A 60-mm arch height yielded a 40% increase in horizontal elongation and a 36% increase in vertical displacement when the plantar fascia was cut, whereas a 20-mm arch height yielded a 13% increase in horizontal elongation and a 14% increase in vertical displacement. A change in arch height from 20 mm to 60 mm increased stiffness of the foot with and without the plantar fascia.