Achilles Tendinopathy: A Runner's Guide to Causes, Symptoms and Recovery

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Achilles tendon pain is one of the most common running injuries we see at Fit and Flex. Alongside plantar fasciitis, Achilles tendinopathy accounts for 6.5–14.2% of all running injuries, depending on the population studied (Mulvad et al., 2018; Lopes et al., 2012). If you are a runner dealing with stiff, painful heels in the morning or sharp pain after a long run, this guide is for you.

 

Below, we break down what Achilles tendinopathy actually is, what causes it, how long recovery takes, and the evidence-based treatments that get runners back on the road.

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What Is Achilles Tendinopathy? 

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Achilles tendinopathy (AT) is a clinical condition characterised by localised pain in the Achilles tendon and functional impairment related to mechanical loading. It can affect two distinct areas:

• Midportion Achilles tendinopathy – pain 2–6 cm above the heel bone. This is the most common type and responds well to conservative treatment.

• Insertional Achilles tendinopathy – pain where the tendon attaches to the heel bone (calcaneus).

(Cooper, 2023; Matthews et al., 2021)​​​ 

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It's Not Just "Inflammation"

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For decades, Achilles tendon pain was labelled "tendonitis" and treated as an inflammatory problem. Modern histological research tells a different story. Achilles tendinopathy is a degenerative condition driven by an abnormal healing response to repetitive microtrauma, characterised by:

• Loss of collagen fibre organisation

• Increased type III collagen

• Proteoglycan accumulation

• Fluid build-up and swelling

• Hypervascularisation (new blood vessel growth)

This shift in understanding has moved clinicians toward a tendon stress and degeneration model rather than treating the condition as simple inflammation (Traweger et al., 2025; Cook & Purdam, 2009; Ohberg et al., 2001; Astrom & Rausing, 1995).

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How Common Is Achilles Tendinopathy?

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Achilles tendinopathy is far more common than most people realise:

• 6% of the general population is affected (Traweger et al., 2025).

• Up to 50% of elite endurance runners experience it during their career.

• Annual incidence in runners: 7.6%; in ultramarathon runners: 2–18.5% (Lagas et al., 2020; Lopes et al., 2012).

• Peak age is over 45, with rates around 8% in this group (Wang et al., 2022).

• General practice incidence: 1.85 per 1,000 adult patients (de Jonge et al., 2011).

 

Most studies show no significant difference between men and women, although some data suggest men may be slightly more affected (Wang et al., 2022).

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Symptoms of Achilles Tendinopathy

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Common symptoms include:

• Achy or sharp pain and stiffness in the lower calf

• A palpable thickening or lump along the tendon

• Localised swelling

• Morning stiffness that improves with movement

• Constant or intermittent pain

• Pain aggravated during or after weight-bearing exercise

• Tenderness along the tendon

• Pain on passive dorsiflexion (pulling toes toward shin)

(Kearney et al., 2015; Tu, 2018)

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If your symptoms match, a clinical assessment can confirm the diagnosis and rule out other causes such as Achilles tendon rupture or referred pain.

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What Causes Achilles Tendinopathy?

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The cause is multifactorial, meaning several intrinsic and extrinsic factors usually combine to trigger symptoms.

 

Intrinsic Risk Factors

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• Prior lower-limb tendinopathy or fracture – the strongest predictor (odds ratio ≈ 6.3 for AT in the preceding 12 months)

• Foot type: flat feet (pes planus) increase forefoot pronation; high arches increase propulsion forces

• Decreased isokinetic plantar-flexor strength

• Abnormal ankle dorsiflexion range of motion

• Increased foot pronation, especially during the stance phase

• Abnormal tendon structure on imaging

• Genetic variants – family history multiplies risk by 5

• Older age

• Running technique – altered force displacement and increased lateral forefoot loading in heel-strikers

(Martin et al., 2018; Wang et al., 2022; van der Vlist et al., 2019; Lee et al., 2019; Lagas et al., 2020)

 

Extrinsic Risk Factors

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• Training errors – sudden increases in volume or intensity (O'Neill et al., 2016)

• Running on hard surfaces (Nichols, 1989)

• Downhill running

• Cold-weather training (van der Vlist et al., 2019)

• Faulty equipment, particularly rigid insoles versus shock-absorbing alternatives (Martin et al., 2018)

 

Medical Conditions and Medications

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• Obesity, hypertension, hyperlipidaemia, and diabetes increase risk (Martin et al., 2018; van der Vlist et al., 2019)

• Fluoroquinolone antibiotics (e.g., ofloxacin) are strongly associated with tendon injury (Medicines and Healthcare products Regulatory Agency, 2023)

 

How Achilles Tendinopathy Develops

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The Achilles is the largest and strongest tendon in the human body (Medina Pabón & Naqvi, 2023). It transmits forces from the gastrocnemius, soleus, and plantaris muscles to the heel during plantarflexion.

When loading exceeds the tendon's ability to repair itself, a cascade begins:

1. Repeated submaximal forces cause collagen cross-links to fail.

2. Damage outpaces repair.

3. The tendon develops proteoglycan accumulation, fluid build-up, hypervascularisation, and disorganised tissue.

4. Persistent low-grade dysfunction sets in.

(Gupton et al., 2023; Cook et al., 2016; (Medina Pabón & Naqvi., 2023; Traweger et al., 2025)

The midportion is vulnerable due to reduced vascular supply as the tendon fibres rotate 90° laterally. The insertion is vulnerable to compressive and shear forces at the heel bone (Kearney et al., 2015).

 

How Long Does Achilles Tendinopathy Take to Heal?

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In a large prospective cohort of runners, median recovery time was 82 days, with a range from 21 to 479 days (Martin et al., 2018). Recovery depends on:

• Severity of the tendon changes

• How early treatment begins

• Adherence to rehabilitation

• Biomechanical factors specific to the individual

 

Most patients improve, but recovery is rarely linear. Setting realistic expectations from the start makes a real difference.

 

Evidence-Based Treatment for Achilles Tendinopathy

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There is no single gold-standard treatment, partly because clinical results vary across studies (Li & Hua, 2016). What the evidence does support is a layered approach: load management, targeted exercise, hands-on therapy, and biomechanical correction.

 

What Works Best

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• Eccentric exercise plus soft-tissue therapy is the most effective combination identified to date (Ko et al., 2023).

• Heavy slow resistance training delivers comparable outcomes to eccentric exercise, with high patient satisfaction (98% vs 76%) at 52 weeks.

• Joint mobilisation improves mobility and function in midportion Achilles tendinopathy.

• Soft-tissue mobilisation increases range of motion (Martin et al., 2018).

• Neuromuscular exercises targeting lower-extremity kinetics and kinematics, particularly eccentric overload during weight-bearing activities.

 

The Fit and Flex Approach

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A common observation in the research is that runners often continue to feel pain even after standard rehabilitation (Martin et al., 2018). At Fit and Flex, our treatment plan addresses this directly:

1. Osteopathic joint and soft-tissue mobilisation to restore movement

2. Progressive loading exercises (eccentric and heavy slow resistance)

3. Biomechanical assessment specific to your running gait

4. Tailored return-to-running programming

 

This combination targets both the tendon and the underlying movement patterns that caused the problem.

 

FAQs

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Is Achilles tendinopathy serious?

 

It is not immediately dangerous, but it can significantly affect activity and quality of life. If left untreated, it may progress and predispose you to an Achilles tendon rupture, which is a far more serious injury.

 

Can I keep running with Achilles tendinopathy?

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In a non-acute phase, running can usually continue if pain stays at or below 3/10 and does not worsen during or after activity. Pain between 0–2/10 is considered safe; 2–5/10 is acceptable while you complete your rehab.

Silbernagel et al. (2007) compared runners who continued running and jumping during rehabilitation to those who switched to walking. Both groups improved at similar rates, suggesting continued running is safe when pain is well controlled.

 

Heel lifts, custom arch supports, or shock-absorbing insoles — which is best?

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• A small study by Lee et al. (2019) found that both heel lifts and customised arch supports reduce tension on the Achilles tendon and may relieve symptoms.

• Tu (2018) also reports benefit from heel lifts and orthotics.

• Martin et al. (2018) found insufficient evidence to recommend one universally, but noted shock-absorbing insoles cut Achilles tendinopathy incidence in half (4% vs 8% with rigid insoles).

 

The best choice depends on your foot type, gait, and footwear — something we assess during your appointment.

 

What is the fastest way to recover?

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The most effective approach combines:

• Eccentric loading exercises

• Smart load management

• Correction of underlying biomechanical issues

• Shockwave therapy, which may accelerate recovery in some cases

 

Quick fixes are rare. Consistent rehab over 8–12 weeks delivers the best outcomes.

 

 

 

References

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Aström, M. and Rausing, A. (1995) ‘Chronic Achilles tendinopathy: a survey of surgical and histopathologic findings’, Clinical Orthopaedics and Related Research, (316), pp. 151–164. Available at: https://pubmed.ncbi.nlm.nih.gov/7634699/ 

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Cook, J.L., Rio, E., Purdam, C.R. and Docking, S.I. (2016) 'Revisiting the continuum model of tendon pathology: what is its merit in clinical practice and research?', British Journal of Sports Medicine, 50(19), pp. 1187–1191. doi: 10.1136/bjsports-2015-095422. Available at: https://www.researchgate.net/publication/301720482_Revisiting_the_continuum_model_of_tendon_pathology_what_is_its_merit_in_clinical_practice_and_research

 

Cook, J.L. and Purdam, C.R. (2009) ‘Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy’, British Journal of Sports Medicine, 43(6), pp. 409–416. doi: 10.1136/bjsm.2008.051193. Available at: https://bjsm.bmj.com/content/43/6/409.long

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Cooper, M.T. (2023) ‘Common painful foot and ankle conditions: a review’, JAMA, 330(23), pp. 2285–2294. doi: 10.1001/jama.2023.23906. Available at: https://jamanetwork.com/journals/jama/article-abstract/2812902 

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de Jonge, S. et al. (2011) ‘Incidence of midportion Achilles tendinopathy in the general population’, British Journal of Sports Medicine, 45(13), pp. 1026–1028. doi: 10.1136/bjsports-2011-090342. Available at: https://pubmed.ncbi.nlm.nih.gov/21926076/ 

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Gupton, M., Özdemir, M. and Terreberry, R.R. (2023) ‘Anatomy, bony pelvis and lower limb: calcaneus’, StatPearls. Available at: https://www.ncbi.nlm.nih.gov/books/NBK519544/

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Kearney, R.S., Parsons, N., Metcalfe, D. and Costa, M.L. (2015) ‘Injection therapies for Achilles tendinopathy’, Cochrane Database of Systematic Reviews, Issue 5, CD010960. Available at: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD010960.pub2/full

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Ko, V.M., Cao, M., Qiu, J., Fong, I.C., Fu, S.C., Yung, P.S. and Ling, S.K. (2023) ‘Comparative short-term effectiveness of non-surgical treatments for insertional Achilles tendinopathy: a systematic review and network meta-analysis’, BMC Musculoskeletal Disorders, 24(1), p. 102. doi: 10.1186/s12891-023-06170-x. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC9903592/

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Lagas, I.F. et al. (2020) ‘Incidence of Achilles tendinopathy and associated risk factors in recreational runners: a large prospective cohort study’, Journal of Science and Medicine in Sport, 23(5), pp. 448–452. doi: 10.1016/j.jsams.2019.12.013. Available at: https://pubmed.ncbi.nlm.nih.gov/31892510/

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Lee, K.K.W., Ling, S.K.K. and Yung, P.S.H. (2019) ‘Controlled trial to compare the Achilles tendon load during running in flatfeet participants using a customized arch support orthoses vs an orthotic heel lift’, BMC Musculoskeletal Disorders, 20(1), p. 535. doi: 10.1186/s12891-019-2898-0. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC6854722/

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Li, H.Y. and Hua, Y.H. (2016) ‘Achilles tendinopathy: current concepts about the basic science and clinical treatments’, BioMed Research International, 2016, p. 6492597. doi: 10.1155/2016/6492597. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC5112330/ 

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Lopes, A.D. et al. (2012) ‘What are the main running-related musculoskeletal injuries? A systematic review’, Sports Medicine, 42(10), pp. 891–905. doi: 10.1007/BF03262301. Available at: https://pubmed.ncbi.nlm.nih.gov/22827721

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Martin, R.L. et al. (2018) ‘Achilles pain, stiffness, and muscle power deficits: midportion Achilles tendinopathy revision 2018’, Journal of Orthopaedic and Sports Physical Therapy. doi: 10.2519/jospt.2018.0302. Available at: https://www.jospt.org/doi/10.2519/jospt.2018.0302

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Matthews, W. et al. (2021) ‘The clinical diagnosis of Achilles tendinopathy: a scoping review’, PeerJ, 9, e12166. doi: 10.7717/peerj.12166. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC8485842/

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Medina Pabón, M.A. and Naqvi, U. (2023) ‘Achilles tendinopathy’, StatPearls. Available at: https://www.ncbi.nlm.nih.gov/books/NBK538149/

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Medicines and Healthcare products Regulatory Agency (2023) Fluoroquinolone antibiotics: reminder of the risk of disabling and potentially long-lasting or irreversible side effects. Available at: https://www.gov.uk/drug-safety-update/fluoroquinolone-antibiotics-reminder-of-the-risk-of-disabling-and-potentially-long-lasting-or-irreversible-side-effects 

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Mulvad, B. et al. (2018) ‘Diagnoses and time to recovery among injured recreational runners in the RUN CLEVER trial’, PLoS ONE, 13(10), e0204742. doi: 10.1371/journal.pone.0204742. Available at: https://pubmed.ncbi.nlm.nih.gov/30312310/

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Nichols, A.W. (1989) ‘Achilles tendinitis in running athletes’, Journal of the American Board of Family Practice, 2(3), pp. 196–203. Available at: https://pubmed.ncbi.nlm.nih.gov/2665426/

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O’Neill, S., Watson, P.J. and Barry, S. (2016) ‘A Delphi study of risk factors for Achilles tendinopathy: opinions of world tendon experts’, International Journal of Sports Physical Therapy, 11(5), pp. 684–697. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC5046962/

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Ohberg, L., Lorentzon, R. and Alfredson, H. (2001) ‘Neovascularisation in Achilles tendons with painful tendinosis but not in normal tendons: an ultrasonographic investigation’, Knee Surgery, Sports Traumatology, Arthroscopy, 9(4), pp. 233–238. doi: 10.1007/s001670100206. Available at: https://esskajournals.onlinelibrary.wiley.com/doi/10.1007/s001670000189

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Physiopedia (2026) ‘Achilles tendinopathy’. Available at: https://www.physio-pedia.com/Achilles_Tendinopathy

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Silbernagel, K.G., Thomeé, R., Eriksson, B.I. and Karlsson, J. (2007) ‘Continued sports activity, using a pain-monitoring model, during rehabilitation in patients with Achilles tendinopathy: a randomized controlled study’, The American Journal of Sports Medicine, 35(6), pp. 897–906. doi: 10.1177/0363546506298279. Available at: https://journals.sagepub.com/doi/10.1177/0363546506298279?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed

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The Newcastle upon Tyne Hospitals NHS Foundation Trust (2025) Achilles tendinopathy. Available at: https://www.newcastle-hospitals.nhs.uk/services/newcastle-occupational-health-service/information-for-staff/physiotherapy/self-help-leaflets/achilles-tendinopathy/

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Traweger, A. et al. (2025) ‘Achilles tendinopathy’, Nature Reviews Disease Primers, 11(1), p. 20. doi: 10.1038/s41572-025-00602-9. Available at: https://www.nature.com/articles/s41572-025-00602-9

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Tu, P. (2018) ‘Heel pain: diagnosis and management’, American Family Physician, 97(2), pp. 86–93. Available at: https://www.aafp.org/pubs/afp/issues/2018/0115/p86.html 

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van der Vlist, A.C. et al. (2019) ‘Clinical risk factors for Achilles tendinopathy: a systematic review’, British Journal of Sports Medicine, 53(21), pp. 1352–1361. doi: 10.1136/bjsports-2018-099991. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC6837257/

 

Wang, Y., Zhou, H., Nie, Z. and Cui, S. (2022) ‘Prevalence of Achilles tendinopathy in physical exercise: a systematic review and meta-analysis’, Sports Medicine and Health Science, 4(1), pp. 1–8. Available at: https://www.researchgate.net/publication/359559294 

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Zhao, G. et al. (2019) ‘HMGB1 mediates the development of tendinopathy due to mechanical overloading’, PLoS ONE, 14(9), e0222369. doi: 10.1371/journal.pone.0222369. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC6764662/