Achilles tendon pain: causes and diagnoses. When should you see a doctor?

What are the causes of Achilles tendon pain? When must special care be taken? Below you can find an overview of the most common causes and diagnoses:

1. Causes of Achilles tendon pain and reasons to tread carefully:
a) the Achilles tendon hurts when doing strength training
b) the Achilles tendon hurts at very low temperatures
c) the Achilles tendon hurts in older athletes
d) the Achilles tendon hurts after periods of inactivity and lack of movement
e) caution is necessary with Achilles tendon injuries
f) caution is necessary in the case of sudden overloading
g) the Achilles tendon hurts when under constant strain/overload
h) caution is necessary in the case of partial Achilles tendon tears that are not fully healed, or micro tears
i) caution is necessary in the case of insufficient recovery periods
j) Achilles tendon pain with other physical causes
k) external causes

2. The most common diagnoses of Achilles tendon pain:
a) achillodynia
b) complete Achilles tendon tear
c) tendinopathy or tendinosis
d) paratendinitis and paratendinopathy
e) achillobursitis
f) other diagnoses related to foot pain
g) tendinitis

When should you see a doctor?

4. What helps to relief from Achilles tendon pain?

1. Causes of Achilles tendon pain and reasons to tread carefully

Achilles tendon pain generally has several causes. Please go through all of the points that may apply.

a) The Achilles tendon hurts when doing strength training

During strength training, particularly with speed-strength loads, the tendon becomes stronger but loses elasticity. This makes it more prone to injury.

Through activities such as strength training, which put the Achilles tendon under a lot of strain, the regeneration of connective tissue (collagen synthesis) is intensely stimulated. What is interesting here is that the amount of collagen is barely increased but the structure of the tendon changes. Thick collagenous fibres are broken down and replaced by thinner fibres (fibrils). This results in the tendon becoming stronger but losing elasticity. Conclusion: although the Achilles tendon is stronger under load, due to the loss of elasticity it is more prone to injury. This must particularly be monitored in the case of speed-strength loads.

b) The Achilles tendon hurts at very low temperatures

In cold conditions, circulation in the muscles and Achilles tendon is reduced, making them more susceptible to damage. When it’s cold outside, you do not only need to warm up your muscles, but also your Achilles tendon.

c) The Achilles tendon hurts older athletes

The older the athlete, the more degenerated the Achilles tendon will be. For this reason, Achilles tendon pain occurs more frequently athletes over 50.

As we get older, the number of cells in the Achilles tendon decreases and the available cells are less active from the point of view of synthesis. Cells responsible for protein biosynthesis are reduced in number. This decreases the ability to regenerate and form new cells. Furthermore, the pH value in the tissue drops due to more metabolic end products such as lactic acid being stored as we age. As a result, the normal synthesis of the cells is affected. Another important change is that the collagenous fibers lose their normal wavelike shape and become flatter and straighter.

With age, circulation in the area of the Achilles tendon is also considerably reduced. Cell synthesis decreases and the collagenous fibers change, which also influences the structure of the Achilles tendon. There is a risk that this can result in an increased susceptibility to injury with subsequent calcification and structural changes in the Achilles tendon.

Calcification involves the formation of fibrocartilage due to reduced circulation combined with small injuries (excessive loading). Calcium crystals are then stored in this cartilage and there is no more circulation through the tissue. This process can be a source of pain.

After this phase, in which calcium is stored, activated macrophages and giant cells spontaneously break the calcium down again. Changes in the structure of the Achilles tendon are to be monitored into old age.

d) The Achilles tendon hurts after periods of inactivity and lack of movement

The longer the foot is kept still or immobilized, the more the Achilles tendon degenerates. Practically the same negative process then takes places as when ageing.

All tissue like the Achilles tendon needs ongoing physiological stimuli (= movement and load) to be able to maintain its normal structure and function. People who work sitting can face reduced blood flow and consequently pain.

e) Caution is necessary with Achilles tendon injuries

Even if the Achilles tendon is not torn, an injury may lead to degeneration with all of the consequences seen in old age. It may also cause pain. What is important here is to allow the Achilles tendon to heal correctly. In most cases, this does not happen as sporting activities are resumed too soon. Then the pain will still be there.


f) Caution is necessary in the case of sudden overloading

Sudden overloading can lead to a total rupture (tear), however, this is quite rare. The rupture is often accompanied by a snapping sound, like the crack of a whip, and intense pain. It is impossible to walk on tiptoe, for example. However, in most cases, a partial tear is most likely. The load is not usually on the whole Achilles tendon but just parts of it and they cannot withstand as much strain. In the case of partial tears, the pain can be felt immediately or is only felt some time later.

Complete ruptures are uncommon because the Achilles tendon normally has a very high load capacity. Partial tears can occur when the Achilles tendon is subject to a load of around one third of its maximum load capacity. Contrary to complete ruptures, they are therefore more common as the Achilles tendon is normally only partially subject to a load and not entirely. Normal loads lengthen the Achilles tendon by approx. 4%. If the tendon becomes even longer, micro-ruptures appear in the bundle of fibers. If extended by 8–12%, a complete rupture occurs, accompanied by intense pain.

g) The Achilles tendon hurts when under constant strain/overload

Even if the load is not so high that part of the tendon tears first time, constant repetition of the load can at some point lead to a partial tear. In the case of constant overloading, it is even more likely that micro-tears will be formed and the tendon will degenerate

Caution is necessary in the case of partial Achilles tendon tears that are not fully healed, or micro-tears

Partial tears, even small tears, are not able to heal properly – because, for example, intensive sporting activity is resumed too soon – the problem will become chronic. This risk is not to be underestimated! This is then referred to as chronic tendinopathy. It is very difficult to heal and the pain will return over and over again.

Important: some speak of tendinitis, that is, inflammation of the tendon. However, this is incorrect, as there is no inflammatory reaction in the tendon. Chronic means that the tendon gets stuck in the healing process, so to speak, and causes problems and pain again and again.

Chronic tendinitis or tendinopathies arise when partial tears (ruptures) are unable to heal. A common reason for this is that they are not placed under enough strain. Small tendon injuries in particular, where there is no inflammatory reaction, often tend to become chronic. For this reason, they are often referred to as chronic tendinitis (‘-itis’ indicates inflammation). It would be more fitting to refer to them as chronic tendinosis or tendinopathy, as in these cases there is no inflammation.

i) Caution is necessary in the case of insufficient recovery periods

Those who start their next session of intensive training too soon after the previous session run the risk of developing Achilles tendon complaints or tendinopathies. After intensive training the tendon needs more than 36 hours to fully recover!

Tendons are constantly undergoing degeneration and regeneration processes. When under load, degeneration increases, but regeneration is also cranked up. For the tendon to regenerate it is important that the corresponding stimulus is present and this must be carefully dosed. It must not be too low as the tendon will not react. However, it must not be too high either as regeneration will stop again and will be masked by the next stage of degeneration.

j) Achilles tendon pain with other physical causes:
  • incorrect foot position and strain on the foot, e.g. flat feet, overpronation
  • foot instability, e.g. after suffering a torn ligament
  • problems in other parts of the body such as the knees, hips, spine, jaw joint
  • neuromuscular problems
  • metabolic disorders (e.g. diabetes)
  • problems in the autonomic nervous system
  • excessive loads during training
  • increasing the load too quickly
  • lack of recovery time
  • no warm-up, especially on cold days
  • training moving too quickly from heel strike to midfoot or forefoot strike

k) External causes:
  • inadequate footwear which is not suitable for the physiology of your foot
  • inadequate insoles which are not suitable for your feet
  • hard ground underfoot
  • cool temperatures, no warm-up
  • certain medicines, e.g. cortisone, antibiotics in the fluorquinolone group

2. The most common diagnoses of Achilles tendon pain

Note: this information is general information and is merely for initial orientation. In the event of ongoing pain, please see a doctor.

a) Achillodynia

The term ‘achillodynia’ is used collectively for diagnosis. However, this is a very broad term. The aim of the following information is to break this down into the four main causes of Achilles tendon pain, whereby tendinopathy is by far the most common:

  • complete or partial Achilles tendon tear
  • tendinopathy in the mid portion or at the base of the tendon
  • bursitis, inflammation of the bursa
  • peritendinitis, inflammation of the gliding tissue around the tendon
b) Complete Achilles tendon tear – sudden snapping sound, similar to the crack of a whip

Intense, stabbing pain, swelling, no longer possible to stand on tiptoe – after a few days this can become a dull pain.

Chronic Achilles tendon tear – the tear has already been existing for some time but is normally noticeable – pain increases when climbing hills or stairs.

c) Tendinopathy - the most common
  • Tendinopathy or tendinosis – problem in the mid portion of the tendon: the tendon can become thickened and hurt when pressed upon, when starting to move in the morning, or after long periods lying down or sitting. Pain may also be felt under load -> pain during sporting activities.
  • Insertional Achilles tendinopathy – problems in the transition to the heel bone: difficult to judge as it can also affect other areas such as the Achilles tendon. In any case: pain when pressing on this point, pain when starting to move, pain when under load.

d) Paratendinitis and paratendinopathy – problems throughout the whole tendon.

However, it is not primarily the tendon that is affected but the connective tissue/gliding layer around the tendon. Pain upon applying pressure or pinching (thumb and index finger around the tendon), however, the tendon is not thickened.

e) Achillobursitis – inflammation of the bursa

Pain and redness in the area just above the heel (above the base of the tendon), especially to the right and left of the tendon. Pain when wearing closed footwear, but not when barefoot. Pain when lifting the foot; swelling and redness as a typical sign of inflammation.
f) Further diagnoses related to foot pain
  • Haglund’s deformity: also linked to pain in the heel, especially when wearing shoes; caused by a protrusion of bone at the back of the heel, which looks like a synovial cyst (highly visible).
  • Heel spur: pain in the heel, but beneath it. This is caused by a thorn-like extension of the heel bone on the sole of the foot, which usually leads to inflammation accompanied by pain.
  • Plantar fasciitis: pain on the sole of the foot; caused by inflammation or degeneration of the large tendon/fascia on the sole of the foot.

g) Tendinitis

This term is often used and is interpreted as inflammation of the Achilles tendon. However, inflammation rarely occurs in the tendon, but rather in the gliding layer or connective tissue around the tendon, so we will not use this term any more here.

3. When should you see a doctor?

  • In the case of recurrent pain
  • If the tendon is extremely swollen
  • If the pain is very strong
  • If you can no longer put your foot down

4. What helps Achilles tendon pain

It is important to know what the diagnosis is and what stage the injury is in. Only then is it possible to treat Achilles tendon pain properly and successfully. 80% of treatment success is secured by a correct diagnosis! Building on this, different treatments can be applied:

a) Achilles tendon treatment
b) Achilles tendinopathy treatment
c) Achilles tendon surgery
d) Achilles tendon exercises
e) Achilles tendon massage
f) Achilles tendon tape
g) Achilles tendon cooling or warming