Definition
Achilles tendinopathy is an overuse condition characterised by pain and a reduced capacity of the Achilles tendon to withstand the mechanical stresses placed on it. It is one of the most common tendinopathies of the lower limb and particularly affects athletes involved in running, jumping, accelerating and changing direction.
The term “tendinitis” is now considered too narrow: Achilles tendinopathy is not simply an inflammation of the tendon. It corresponds to a situation in which the mechanical capacity of the tendon becomes insufficient relative to the stresses it is subjected to. The tendon is a living tissue capable of adapting to load — progressive mechanical stimulation leads to structural and functional adaptation that allows it to withstand increasing stresses. Conversely, too rapid an increase in load, insufficient recovery or a reduction in its mechanical capacity can cause symptoms to appear.
Achilles tendinopathy should therefore be understood as an imbalance between the capacity of the tendon and the load placed on it, rather than as a simple inflammation. Two anatomical forms must be distinguished, because the mechanical stresses and the principles of rehabilitation are not exactly the same depending on the location: mid-portion tendinopathy (mid-portion), usually located between 2 and 6 cm above the calcaneal insertion, and insertional tendinopathy, located at the junction between the tendon and the calcaneus.
Anatomy
The Achilles tendon is the terminal tendon of the triceps surae. It is formed by the convergence of the medial gastrocnemius, the lateral gastrocnemius and the soleus, and inserts on the posterior surface of the calcaneus.
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It transmits the force produced by the triceps surae to the foot and is mainly involved in plantar flexion of the ankle. It also plays a major role in storing and releasing elastic energy: during running, it behaves partly like a biological spring. During the stance phase, it deforms under mechanical stress and stores energy, which is then released at push-off. This property improves propulsion efficiency, reduces the energy cost of running, absorbs some of the stresses and contributes to ankle control. This capacity to store and then release energy depends in particular on the stiffness and structure of the tendon, the strength of the triceps surae and the rate at which load is applied.
Tendon biomechanics during running
The Achilles tendon is subjected to considerable mechanical stress during running: the force developed by the triceps surae can amount to several times body weight and increases sharply during fast running, accelerations, uphill running, jumps and changes of direction.
However, the stress applied to the tendon depends as much on the absolute load as on the way it is applied. A tendon can perfectly well tolerate a high load if it is introduced gradually and its mechanical capacities are sufficient; conversely, a relatively moderate load can become symptomatic when it is introduced abruptly on a deconditioned tendon.
The gastrocnemius and soleus are the main drivers of the tendon: the soleus plays a major role during running and activities requiring high force production in plantar flexion, so a reduction in its strength or endurance reduces the system’s capacity to absorb and redistribute stresses. The speed at which force is applied also matters: easy jogging, an acceleration and a jump do not load the tendon in the same way. This is why rehabilitation must gradually progress the load along several dimensions — volume → strength → speed → energy storage/release → sport-specific stresses — which explains why a patient may be able to walk without pain yet be unable to run, jump or accelerate.
Epidemiology
Achilles tendinopathy is particularly common in sports involving repeated running and jumping stresses. It can also occur in people who are not very active, particularly with age or in the presence of metabolic factors: the risk increases with age, with a particularly high frequency in middle-aged athletes.
In runners, it accounts for approximately 6 to 18% of running-related injuries, making it one of the most common conditions. It is also a risk factor for prolonged reduction in sports participation, particularly when it becomes chronic.
Causes & risk factors
Training load
The main triggering factor is usually a change in training load. Typical situations are: returning to running after a break, a rapid increase in mileage, an increase in speed, the introduction of interval training, a large increase in elevation gain, an increase in the number of sessions, a return to a team sport or the abrupt introduction of plyometrics.
The problem is therefore not necessarily an excessive load in absolute terms: most often it is a load that is excessive relative to the tendon’s current capacity.
Recovery
The tendon needs time to adapt. A succession of demanding sessions without sufficient recovery can promote the onset of symptoms. Sleep, energy availability and overall recovery should therefore be included in the analysis in the same way as training volume.
Biomechanical factors
Certain factors can contribute to overload: a deficit in triceps surae strength or endurance, limited ankle mobility, poor control of the lower limb, a significant change in stride, a recent change of shoes or an abrupt increase in cadence or stride length. However, none of these characteristics should be considered in isolation as a definite cause of tendinopathy.
Metabolic factors
Certain conditions are associated with an increased risk of tendinopathy: diabetes, dyslipidaemia, obesity, certain inflammatory diseases or metabolic disorders. Smoking is also an unfavourable factor.
Medication
Fluoroquinolones are associated with an increased risk of tendinopathy and tendon rupture. Systemic corticosteroids can also contribute to weakening the tendon, particularly when combined with other risk factors.
Symptoms
The main symptom is pain at the back of the ankle. The clinical presentation depends on the location.
Mid-portion tendinopathy. The pain is usually located between 2 and 6 cm above the calcaneus. It is often triggered by running, accelerating, uphill running, jumping or calf exercises. Morning stiffness is common; the pain may initially ease after a few minutes of activity and then return after exercise, gradually becoming more intense and appearing earlier as the condition progresses.
Insertional tendinopathy. The pain is located directly at the insertion of the tendon on the calcaneus. It is often aggravated by the combination of load, marked dorsiflexion and compression of the tendon against the calcaneus — which explains why some exercises traditionally used for mid-portion forms may be poorly tolerated in insertional forms. Wearing stiff shoes or shoes that press on the back of the heel can also worsen symptoms.
Clinical examination
The diagnosis is mainly clinical. The examination begins by pinpointing the location of the pain; palpation usually reproduces the symptoms. The clinician looks for mid-portion or insertional pain, tendon thickening or irregularity, pain on loading the tendon, and a deficit in triceps surae strength or endurance.
The Single Leg Heel Rise Test is a particularly useful functional test: the patient performs repeated heel raises on one leg, which makes it possible to assess the number of repetitions, heel height, pain, fatigue, asymmetry and quality of movement. The aim is not only to look for pain but to assess the functional capacity of the triceps surae–Achilles tendon complex. In athletes, the assessment can gradually include dynamic tests (two-legged and single-leg jumps, bounds, running, accelerations, changes of direction), introduced according to the level of recovery.
Further tests
Ultrasound
Assesses tendon thickness and architecture, fibrillar abnormalities, hypoechoic areas, vascularisation, and fissures or partial tears. Also allows dynamic assessment.
MRI
Useful when the diagnosis is uncertain, the course is atypical, a partial tear is suspected, another condition is being looked for or surgery is being considered. Allows examination of the tendon, its insertion, the bursae and the adjacent bone structures.
A word of caution about imaging
A structural abnormality of the tendon does not necessarily mean that it is responsible for the pain: ultrasound or MRI abnormalities can be found in asymptomatic patients. The diagnosis must therefore always combine imaging and clinical findings.
Differential diagnoses
Achilles tendon rupture (complete or partial)
Sudden pain with a snapping or whip-like sensation, associated with loss of plantar flexion strength — this should prompt an immediate search for a rupture, and is to be distinguished from the gradual onset typical of tendinopathy.
Retrocalcaneal or superficial bursitis
Pain and swelling more focused over the peritendinous bursae, often worsened by footwear, rather than diffuse pain in the mid-portion or at the insertion of the tendon.
Posterior ankle impingement / Haglund's disease
Posterior pain related to bony impingement or a prominence of the posterosuperior calcaneus, often worsened by forced plantar flexion or footwear, to be differentiated from pure insertional tendinopathy.
Other periarticular tendinopathies
Tendinopathy of the plantaris, tibialis posterior or flexor hallucis longus: pain and palpation point to a tendon path different from that of the Achilles tendon.
Calcaneal stress fracture
Deep bone pain, often triggered by weight-bearing and percussion of the calcaneus, in a context of repeated mechanical overload.
Sural nerve neuropathy
Pain with a neurogenic component (burning, electric shock-like sensations, sensory disturbances) along the course of the nerve, with no direct link to loading of the tendon.
Treatment
General principles and load management
Treatment of Achilles tendinopathy is based on three pillars: load management (temporarily reducing the stresses that exceed the tendon's capacity), progressive strengthening (increasing the capacity of the triceps surae and the tendon to produce and withstand high forces) and the gradual reintroduction of sport-related stresses, following the progression strength → speed → impacts → running → acceleration → sport-specific work. Complete rest is rarely necessary.
Pain can be used as a load-monitoring tool rather than simply as a signal to stop. Moderate pain during exercise, up to about 5/10, may be acceptable provided that it does not gradually worsen during the session, does not significantly alter movement, returns to its usual level the next day and that morning stiffness does not increase in a lasting way. The tendon's behaviour over the following 24 hours is therefore the key element in determining whether the load was appropriate — replacing the logic of "pain = stop" with "pain = information about the tolerated load".
Physiotherapy rehabilitation: progressive strengthening (gold-standard treatment)
When the tendon is very painful, the first step is to restore a basic load capacity: isometric contractions, two-legged heel raises, assisted single-leg heel raises, low-load strengthening. The aim is not immediate disappearance of pain but progressive stimulation of the tendon.
The work then progresses towards heavier loads, with the straight-knee heel raise (mainly targeting the gastrocnemius) and the bent-knee heel raise (placing greater demand on the soleus), performed progressively on both legs, then on one leg, then with added load, increasing the number of repetitions, the load, the range of motion, the difficulty or the speed. Heavy Slow Resistance (HSR) — slow movements with a progressively increasing load — is a particularly useful strategy for restoring maximal strength, endurance and the tendon's capacity to withstand high stresses; however, there is no need to follow a strict HSR protocol, as the key element remains load progression, and no strengthening method has shown systematic superiority over the others.
In insertional forms, particular attention should be paid to compression of the tendon against the calcaneus: at the start of treatment, it is generally preferable to limit heel raises with the heel dropping very low, aggressive calf stretches and exercises that cause strong compression of the insertion, working through a more neutral range before gradually increasing it according to tolerance. A temporary heel lift can also reduce the compression and tension on the painful area.
Restoring power and returning to sport
Once strength has been sufficiently restored, the tendon must gradually be exposed to faster loads — two-legged then single-leg jumps, bounds, skipping rope, small repeated hops, reactive exercises — in order to restore its capacity to store and then rapidly release energy, an essential step for athletes involved in running, jumping or changing direction. The final phase gradually brings the exercises closer to the real demands of the sport; for a runner: walking → easy jogging → continuous running → accelerations → hills → interval training → maximal speed.
The return to running follows a similar progression: well-tolerated brisk walking, then alternating walking and running (for example 1 minute of running / 2 minutes of walking, 8 to 10 cycles), a gradual increase in running time, continuous running, then an increase in speed and the reintroduction of specific stresses (hills, interval training, changes of direction, long sessions) — without simultaneously increasing volume, speed, elevation gain and frequency.
Progression should never be based on a simple calendar but on functional criteria: controlled pain with no progressive worsening, a return to its usual level within 24 hours, stable morning stiffness, progress in triceps surae strength, improvement in the number and quality of heel raises, and good tolerance of dynamic exercises. Before a full return to sport, the aim is low and stable pain, a good capacity for single-leg heel raises without significant asymmetry, satisfactory tolerance of jumps and plyometric exercises, and well-tolerated continuous jogging, accelerations and changes of pace.
Complementary treatments
Extracorporeal shockwave therapy
May be considered in some chronic forms, but should remain an adjunct to progressive loading rather than a stand-alone treatment.
Heel lift
Can temporarily reduce tension and compression on the tendon, particularly useful in insertional forms.
Orthotic insoles
Not routine: may be offered when a clearly identified biomechanical abnormality contributes to the symptoms.
Non-steroidal anti-inflammatory drugs (NSAIDs)
May provide occasional symptomatic benefit, but are not the underlying treatment of the tendinopathy.
Corticosteroid injections
Intratendinous injections should be avoided because of the risk of weakening and rupture of the tendon.
PRP (platelet-rich plasma)
The available evidence remains insufficient to recommend PRP as a first-line treatment.
Surgery
Surgery is rarely necessary. It may be discussed in very disabling chronic forms when the diagnosis is certain, conservative management has been properly carried out, several months of rehabilitation have not produced sufficient improvement and the overload factors have been identified and corrected. Procedures may include tendon debridement, resection of pathological tissue, treatment of calcifications, treatment of Haglund’s disease or, in some severe forms, tendon repair or reconstruction. It should only be considered after a full analysis of the situation.
Recovery time
Achilles tendinopathy is a condition that generally progresses slowly. Improvement may be seen within a few weeks, but full recovery of tendon capacity may take several months. The duration depends in particular on how long the symptoms have been present, the location, functional severity, sporting load, age, metabolic factors and the quality of rehabilitation.
It is important to remember that less pain does not mean full tendon recovery: a patient may quickly feel better while still having insufficient capacity to withstand the stresses of intense sport.
Prevention
Prevention is mainly based on maintaining sufficient tendon capacity: regular strengthening of the triceps surae, single-leg exercises, power work, plyometrics for athletes and gradual exposure to fast running. Loads should be increased gradually, with particular attention to periods of return after a break.
The key principle is not to ask the tendon to do in one week what it has not been prepared to do over the previous weeks.
Frequently asked questions
Can I keep running with Achilles tendinopathy?
Do I need to be completely pain-free to do strengthening exercises?
Should you stop sport completely?
Are eccentric exercises essential?
HSR or eccentric: which should I choose?
Do I need an MRI?
Is shockwave therapy effective?
Can injections be used?
How long does it take to heal?
Can recurrence be prevented?
Common mistakes
Prolonged complete rest, when adapting the load is almost always preferable.
An abrupt return to training as soon as the first improvement is felt.
No strengthening of the triceps surae muscles.
Relying solely on stretching, massage or other passive treatments.
Increasing training volume and intensity at the same time.
Resuming interval training or hill work before triceps surae strength has been restored.
Changing shoes abruptly without a gradual transition.
Focusing on treating the imaging findings rather than the patient and their symptoms.
Key points — Institut Basque du Coureur
Achilles tendinopathy is not simply an inflammation of the tendon: above all, it reflects an imbalance between the capacity of the tendon and the stresses placed on it. Treatment is based on smart load adjustment, followed by a structured progression of strengthening, from strength to power, and finally to sport-specific stresses. Complete rest is rarely necessary. Recovery takes time, and the return to sport should be guided by functional criteria rather than a simple timeframe.
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- Silbernagel KG, Hanlon S, Sprague A. Current Clinical Concepts: Conservative Management of Achilles Tendinopathy. J Athl Train. 2020.
- de Vos RJ, van der Vlist AC, Zwerver J, et al. Dutch Multidisciplinary Guideline on Achilles Tendinopathy. Br J Sports Med. 2021.
- Scott A, et al. ICON 2019 — International Scientific Tendinopathy Symposium Consensus. Br J Sports Med. 2020.
- Malliaras P, Barton CJ, Reeves ND, Langberg H. Loading Programmes in Tendinopathy. Sports Med. 2013.
- Silbernagel KG, Thomeé R, Eriksson BI, Karlsson J. Continued Sports Activity Using a Pain-Monitoring Model During Rehabilitation in Patients with Achilles Tendinopathy. Am J Sports Med. 2007.
- Grävare Silbernagel K, Brorsson A, Lundberg M. The Majority of Patients with Achilles Tendinopathy Recover with Nonoperative Treatment. Am J Sports Med.
- Nørregaard J, Larsen CC, Bieler T, Langberg H. Eccentric Exercise in Treatment of Achilles Tendinopathy.
- O'Neill S, Barry S, Morrissey D. Do Physical Interventions Improve Clinical Outcomes in Achilles Tendinopathy? Br J Sports Med.
- TENDINS-A Study Group. TENDinopathy Severity Assessment — Achilles: Development and Validation. Br J Sports Med. 2024.
- Ardern CL, Glasgow P, Schneiders A, et al. 2016 Consensus Statement on Return to Sport from the First World Congress in Sports Physical Therapy, Bern. Br J Sports Med. 2016.
Physiotherapy protocol for this injury
Découvrez notre protocole de rééducation détaillé pour achilles tendinopathy : exercices adaptés, progression structurée et modalités de reprise.
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