April 2010

The epidemiology of plantar fasciitis

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Up to 10% of the population may present with heel pain over the course of their lives, which underscores the importance of practitioner familiarity with the diagnosis of plantar fasciitis and the associated risk factors, both intrinsic and extrinsic.

by Capt. Danielle L. Scher, MD; Lt. Col. Philip J. Belmont, Jr., MD; and Maj. Brett D. Owens, MD

Plantar fasciitis is the most common cause of heel pain presenting to the outpatient clinic.1 Although thought of as an inflammatory process, plantar fasciitis is a disorder of degenerative changes in the fascia, and may be more accurately termed plantar fasciosis.2 Plantar fasciitis is diagnosed on the basis of a history of pain on taking the first few steps in the morning, worsening pain with weightbearing, and pain and tenderness to palpation over the medial calcaneal tubercle.1-5 Patients may have decreased ankle dorsiflexion secondary to a tight Achilles tendon, which may lead to a compensatory pronation of the foot.4 Up to one third of patients with plantar fasciitis will present with bilateral symptoms.6

On examination, plantar fasciitis must be distinguished from other causes of plantar heel pain. For example, fat-pad atrophy occurs in elderly patients with pain in the central heel. These patients usually do not complain of pain upon first weight bearing in the morning.7 Tarsal tunnel syndrome is described as burning pain along the area of the posterior tibial nerve inferior to the medial malleolus. Finally, a calcaneal stress fracture is confirmed on examination with use of the squeeze test, tenderness on mediolateral compression of the calcaneus.7

Etiology

Plantar fasciitis is multifactorial in etiology. Intrinsic factors include age, excessive foot pronation, obesity and limited ankle dorsiflexion;1,6,8-12 extrinsic factors include occupational prolonged weightbearing, inappropriate shoe wear, and rapid increases in activity level.1,8,12 These factors combine to create a pathologic overload of the plantar fascia at the calcaneal insertion, causing microtears in the fascia that subsequently lead to perifascial edema and increasing heel pad thickness.2,13,14 As microtears within the fascia increase in size, they may coalesce to form a large symptomatic mass that causes the increase in heel pad thickness and can be identified during surgery. These changes in fascial thickening, particularly in the proximal portion of the plantar fascia extending to the calcaneal insertion, and edema of the adjacent fat pad and underlying soft tissues can typically be seen on magnetic resonance imaging studies.15 Inflexibility of the posterior structures of the foot, combined with weakness of the plantar flexors during pushoff, alters the normal biomechanics of the foot, creating an environment of decreased efficiency of force absorption and production.14 The decrease in force absorption contributes to the overload of the plantar fascia and increasing degenerative changes, which include collagen necrosis, angiofibroblastic hyperplasia, chondroid metaplasia and matrix calcification.2 Plantar fasciitis can also be associated with various seronegative spondyloarthropathies, but in approximately 85% of cases there are no known systemic factors.1,15,16

In runners, plantar fasciitis is primarily believed to be an overuse injury combined with training errors, training surfaces, biomechanical alignment and muscle dysfunction and inflexibility. For example, excessive pronation of the foot leads to increased tension on the plantar fascia during the stance phase of running.18 In athletes who are just beginning their training programs, the lower limb muscles may have yet to develop the necessary strength and flexibility, and shock absorption can be negatively affected.17

Epidemiology

Plantar fasciitis is an important public health disorder as it is the most common cause of heel pain in the outpatient setting.1 Ten percent of people in the United States may present with heel pain over the course of their lives, with 83% of these patients being active working adults between the ages of 25 and 65 years old.3,4 Two large national data sets of ambulatory care data (excluding visits to podiatrists or federal, military, or Veterans Administrations facilities) from the Centers for Disease Control and Prevention’s National Center for Health Statistics found that plantar fasciitis accounts for an average of one million patient visits per year to medical doctors.4 Sixty-two percent of these visits were made to general medicine clinics, while 31% of patients were evaluated by orthopaedic or general surgeons. Additionally, a recent survey of members of the American Podiatric Medical Association revealed that plantar fasciitis/heel pain was the most prevalent condition being treated in podiatric clinics.19 Within the current literature, prevalence rates of plantar fasciitis among a population of runners have been shown to be between 4% and 22%.20,21

Rano et al11 found that the average age of the patients presenting to their facility with heel pain was almost 10 years higher than controls who presented for other reasons. Matheson et al’s retrospective review of 1407 patients from an outpatient sports medicine clinic, found that younger athletes had a lower prevalence of plantar fasciitis (2.5%) than older athletes (6.6%).17 The association of plantar fasciitis with increasing age is consistent with the histopathological findings of degenerative, rather than inflammatory, changes within the plantar fascia.2 These degenerative findings support the hypothesis that plantar fasciitis is secondary to repetitive microtrauma caused by prolonged weightbearing activities.13 The constant overload inhibits the normal repair process, resulting in collagen degeneration, which causes both structural changes and perifascial edema.15,22 These changes in turn lead to a thicker heel pad, which has been shown to be associated with pain in individuals with plantar fasciitis.12,13 Increasing heel pad thickness leads to a loss of heel pad elasticity; both of these factors are associated with increasing age and increasing BMI.23 The decrease in elasticity of the fascia seen with increasing age is associated with a decrease in shock absorbing capabilities,23 which may be a result of the degenerative fascia’s inability to resist normal tensile loads.22 It is this decrease in shock absorbing capability that is believed to cause the pain associated with plantar fasciitis.

The current literature is inconsistent regarding the association between sex and plantar fasciitis, with some studies showing an increased prevalence in men,18,24 while others show an increased prevalence in women.11,25 In a retrospective case-control study of running athletes, Taunton et al found a significant sex difference within their study population, as 54% of those affected were male and 46% were female. In contrast, a prospective study including athletes of varying skill levels by Rano et al11 found a higher percentage of women in the heel pain group than in the control group (66.1% compared with 42.6%; p = 0.015). There are no theories within the current literature hypothesizing the reason for a difference in the prevalence of plantar fasciitis between the two sexes, whether it be a function of different hormones or structural differences caused by genetic variations, as is suggested by the increased incidence of anterior cruciate ligament tears in women compared with men.

Increased body weight10 and increased body mass index (BMI)6,8,9,11 have been shown to be significant risk factors for plantar fasciitis, with a BMI of more than 30 kg/m2 having an odds ratio of 5.6 (95% confidence interval, 1.9 to 16.6; p < 0.01) compared with a BMI of less than 25 kg/m2.  Frey and Zamora9 demonstrated a 1.4-fold increased probability of plantar fasciitis being diagnosed in an overweight or obese patient. Rome et al13 suggested that BMI is not related to plantar fasciitis pain in the athletic population, but other factors such as a low estrogen levels in female athletes leading to a reduction in the elasticity of collagen may predispose these patients to plantar fasciitis. Riddle et al8 hypothesized that reduced ankle dorsiflexion is the most important risk factor for the development of plantar fasciitis, as the greater the limitation in ankle dorsiflexion, the greater the amount of compensatory foot pronation and therefore the  higher level of loading on the plantar fascia. A study by Scott et al26 found that older patients (mean age 80.2) had reduced ankle range of motion compared with younger patients (mean age 20.9). An exponential relationship between decreasing ankle dorsiflexion and the risk of developing plantar fasciitis has been found, with individuals who have 0o of dorsiflexion or less having an odds ratio of 23.3 (95% confidence interval, 4.3 to 124.4).8 Foot pronation alone, as measured by the Foot Posture Index,27 has also been shown to be significantly greater in patients with chronic plantar heel pain.6

In addition to these intrinsic factors, various extrinsic factors have been related to the development of plantar fasciitis. Several studies have shown an association between work-related prolonged weightbearing and plantar fasciitis.8,24,28,29 In their case series, Lapidus and Guidotti’s patient population included a predominance of occupations that necessitate continual standing or walking, such as waiters, maids, and kitchen workers.  In addition, each heel strike during running causes compression of the heel pad up to 200% of body weight.30 Therefore, in individuals who may not have adequate muscle strength or flexibility, and therefore have decreased shock-absorbing capabilities, the initiation of a new training program can exacerbate overloading of the plantar fascia.30 Increases in tensile loading, seen with new increases in running intensity or frequency and changes in general footwear have been associated with overloads of the plantar fascia leading to microtears.14 In particular, firm footwear may exacerbate the developing plantar fasciitis in these patients.28 Additionally, plantar fasciitis has also been associated with young individuals engaging in sports involving jumping.15

In order to determine epidemiological risk factors and the current incidence of plantar fasciitis within a population of individuals with a high level of physical activity, Scher et al31 accessed a database from the United States Armed Forces. The United States Armed Forces represent a physically active population of ethnically diverse male and female service members with generally high occupational demands. They participate in daily, organized physical fitness training programs and are subject to the physical rigors of repeated combat deployments. The inability to meet these physical requirements secondary to a medical condition, such as plantar fasciitis, may necessitate a medical discharge from military service. In this population, the authors chose to look at various epidemiological risk factors in order to identify groups at high risk of developing plantar fasciitis. The authors used the Defense Medical Epidemiology Database, which compiles ICD-9 coding information for every patient encounter in a military treatment facility.

The overall incidence of plantar fasciitis in the military population was 10.55 per 1,000 person-years. Female sex; black race; junior enlisted, senior enlisted and senior officer rank groups; military service in the Army or Marines; and age greater than 24 years old were found to be significant risk factors for the development of incident plantar fasciitis when compared to male sex, white race, junior officers rank, service in the Air Force, and age 20 to 24, respectively. Female subjects, when compared with male subjects, had a significantly increased incidence rate ratio for plantar fasciitis of 1.95 (95% CI 1.93-1.98).  These findings are based on incidence rates, but tend to correlate with prevalence data seen within the existing literature.

Summary

As 10% of the population may present with heel pain over the course of their lives, a familiarity with the diagnosis and risk factors for plantar fasciitis is important for both primary care and specialty practitioners. Obesity, decreased ankle dorsiflexion, a pronated foot, and increasing age are important intrinsic risk factors that have been associated with plantar fasciitis. The extrinsic risk factors include prolonged occupational weightbearing, increasing activity levels, and inappropriate shoe wear. With the knowledge of specific risk factors for the development of plantar fasciitis, the next step is to develop preventive measures, such as plantar-specific stretching programs and changes in footwear, to decrease the current incidence of this disorder.

Capt. Danielle L. Scher, MD, and Lt. Col. Philip J. Belmont, Jr., MD, are orthopedic surgeons in the department of surgery at William Beaumont Army Medical Center in El Paso, TX. Maj. Brett D. Owens, MD, is in the department of orthopaedic surgery at Keller Army Hospital in West Point, NY.

Disclosure: Each author certifies that he or she has no commercial associations (e.g., consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.

The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the Department of Defense or United States government.

REFERENCES

1. Singh D, Angel J, Bentley G, Trevino SG. Fortnightly review. Plantar fasciitis.  BMJ 1997;315(7101):172-175.

2. Lemont H, Ammirati KM, Usen N. Plantar fasciitis. A degenerative process (fasciosis) without inflammation. J Am Podiatr Med Assoc 2003;93(3):234-237.

3. Crawford F, Atkins D, Edwards J. Interventions for treating plantar heel pain. Cochrane Database Syst Rev 2000;(3):CD000416.

4. Riddle DL, Schappert SM.  Volume of ambulatory care visits and patterns of care for patients diagnosed with plantar fasciitis: A national study of medical doctors.  Foot Ankle Int 2004;25(5):303-310.

5. Wolgin M, Cook C, Graham C, Mauldin D. Conservative treatment of plantar heel pain: long-term follow-up. Foot Ankle Int 1994;15(3):97-102.

6. Irving DM, Cook JL, Young MA, Menz HB. Obesity and pronated foot type may increase the risk of chronic heel pain: a matched case-control study.  BMC Musculoskelet Disord 2007;8:41.

7. Buchbinder R. Clinical practice. Plantar fasciitis. N Engl J Med 2004;350(21):2159-2166.

8. Riddle DL, Pulisic M, Pidcoe P, Johnson RE. Risk factors for plantar fasciitis: A matched case-control study. J Bone Joint Surg Am 2003;85(5):872-877.

9. Frey C, Zamora J. The effects of obesity on orthopaedic foot and ankle pathology.  Foot Ankle Int 2007;28(9):996-999.

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11.  Rano JA, Fallat LM, Savoy-Moore RT. Correlation of heel pain with body mass index and other characteristics of heel pain. J Foot Ankle Surg 2001;40(6):351-356.

12.  Amis J, Jennings L, Graham D, Graham CE. Painful heel syndrome: radiographic and treatment assessment. Foot Ankle 1988;9(2):91-95.

13.  Rome K, Campbell R, Flint A, Haslock I. Heel pad thickness—a contributing factor associated with plantar heel pain in young adults. Foot Ankle Int 2002;23(2):142-147.

14.  Kibler WB, Goldberg C, Chandler TJ. Functional biomechanical deficits in running athletes with plantar fasciitis.  Am J Sports Med 1991;19(1):66-71.

15.  Narvaez JA, Narvaez J, Ortega R, et al. Painful heel: MR imaging findings.  Radiographics 2000;20(2):333-352.

16.  Furey JG.  Plantar fasciitis. The painful heel syndrome. J Bone Joint Surg Am 1975;57(5):672-673.

17.  Matheson GO, Macintyre JG, Taunton JE, et al. Musculoskeletal injuries associated with physical activity in older adults. Med Sci Sports Exerc 1989;21(4):379-385.

18.  Taunton JE, Ryan MB, Clement DB, et al. A retrospective case-control analysis of 2002 running injuries. Br J Sports Med 2002;36(2):95-101.

19.  Fischer Associates. 2002 podiatric practice survey. Statistical results. J Am Podiatr Med Assoc 2003;93(1):67-86.

20.  Rome K, Howe T, Haslock I. Risk factors associated with the development of plantar heel pain in athletes. The Foot 2001;11(3):119-125.

21.  Ballas MT, Tytko J, Cookson D. Common overuse running injuries: diagnosis and management. Am Fam Physician 1997;55(7):2473-2484.

22.  Wearing SC, Smeathers JE, Yates B, et al. Sagittal movement of the medial longitudinal arch is unchanged in plantar fasciitis. Med Sci Sports Exerc 2004;36(10):1761-1767.

23.  Prichasuk S, Mulpruek P, Siriwongpairat P. The heel-pad compressibility. Clin Orthop Relat Res 1994;(300):197-200.

24.  Lapidus PW, Guidotti FP. Painful heel: Report of 323 Patients with 364 painful heels. Clin Orthop Relat Res 1965;39:178-186.

25.  Davis PF, Severud E, Baxter DE.  Painful heel syndrome: results of nonoperative treatment. Foot Ankle Int 1994;15(10):531-535.

26.  Scott G, Menz HB, Newcombe L. Age-related differences in foot structure and function. Gait Posture 2007;26(1):68-75.

27.  Redmond AC, Crosbie J, Ouvrier RA.  Development and validation of a novel rating system for scoring standing foot posture: the Foot Posture Index. Clin Biomech 2006;21(1):89-98.

28.  Sadat-Ali M. Plantar fasciitis/calcaneal spur among security forces personnel.  Mil Med 1998;163(1):56-57.

29.  Pfeffer G, Bacchetti P, Deland J, et al. Comparison of custom and prefabricated orthoses in the initial treatment of proximal plantar fasciitis. Foot Ankle Int 1999;20(4):214-221.

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31.  Scher DL, Belmont PJ Jr, Bear R, et al. The incidence of plantar fasciitis in the United States military. J Bone Joint Surg Am 2009;91(12):2867-2872.

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3 Responses to The epidemiology of plantar fasciitis

  1. Your are right about morning pain – I could hardly walk when I got out of bed. My case was correctly diagnosed and my podiatrist fitted me with a custom pair of insoles. That was25 years ago and I have had no recurrence since. Thank you for a very comprehensive review.

    Bruce Walseth

  2. Harvey Johnson says:

    My only requirement for etiology of plantar fasciitis is that a person is vertical. I am not being sarcastic saying this. I am always struck that clinicians have to narrow down etiologies for PF when it happens to virtually all foot types and all ages of people whether they are active or not: whether they are fat or skinny and whether or not they pronate or have stable arches. Chronic PF is one of the top 5 pathologies I see and I cannot for the life of me pin down etiology except maybe in elite extremely active athletes. And who is to say that it is their activity level is causing the problem? I have people who present with morning pain and people who present with more pain at the end of the day. And I have people who present with both. I see every single foot type and age group and activity level present with PF. I believe it is an area of the body that has probably plagued mankind with inflammation ever since we went from four limbs to two limbs.

  3. melvin says:

    Do you note any direct correlation between bilateral plantar fasciitis and chronic knee pain?

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