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Achilles Tendon Disorders – Tendinopathy – Basic Science & Clinical Treatments

Achilles tendon problems are one of the most frequent ankle / lower leg conditions. They can be characterised by a combination of symptoms including:

  • Pain
  • Swelling
  • Impaired performance
  • Tightness
  • Visible lump formations

The Achilles tendon is much longer and larger than most people initially realise. Its origin is as a wider, flatter tendon streaming mainly from the lower end of the Gastrocnemius muscle (the larger, twin-headed calf muscle) & its ‘muscle partner’ the Soleus Muscle (a flat muscle located deeper, underneath the twin-headed calf muscle). The tendon then travels downwards gradually becoming a more condensed ‘rope type’ tendon until reaching Its insertion (anchoring point) at the rear of the heel bone (Calcaneus). Here it widens slightly encompassing and gripping the rear of this bone.

HTC Blog - Achilles Tendon Diagram

This tendon, when healthy is extremely strong and relatively flexible.

Generally, Achilles tendinopathy would be broadly placed in two main categories according to symptom location:

  • Insertional = Approximating its fixation/anchoring point at the heel.
  • Non-insertional = Parts of the main tendon not related to its insertion area.
HTC Blog - Achilles Tendon demo

The Science…

Traditionally, many terms have been used to describe disorders affecting this tendon, including tendinitis, tendinosis, and paratenonitis. However, histopathological studies (studies of tissue diseases and deterioration) have found these disorders are mainly as a result of a failed healing response causing degenerative changes in the tendon. These changes then include all three of the aforementioned names and occur in 3 different and continuous stages i.e. reactive tendinitis, tendon disrepair, and degenerative tendinopathy.

What we know is that the tendon includes a multitude of long collagen fibres. Collagen fibres come in varying forms with varying characteristics. When healthy these particular tendons fibres are Collagen Type I & II. These fibres are comparable with spiders-web threads i.e. flexible, semi-elastic & very strong for their size.

HTC Blog - Achilles Tendon Structure

With Achilles tendinopathy fibre disorganisation (mis-formation), fragmentation (micro-damage) and morphing (tissue type & shape alterations) occur. During this process, we know that a percentage of the tendon’s fibres alter their type to Type III collagen. This type is stiffer, less flexible, and is usually associated with warped structure changes eventually developing to micro-tears.

At later stages, the body also initiates more direct blood flow to these disturbed and malformed tendon areas by building tiny arteries called capillaries within the locality of the disrupted area. This is called neovascularisation.

Aetiology (Causes/set of causes) of Achilles Tendinopathy

We do not yet understand fully why this condition and its associated tissue changes occur but evidence to date strongly suggests that almost all incidents of either acute or chronic Achilles tendinopathy are due to changes of a mechanical nature & / or use, i.e. the tendon is unable to adapt to the altered mechanical forces being applied to it.

Below are some examples:

  • A change in the normal bio-mechanical line of force through the tendon. – e.g. Prolonged inward leaning of the ankle pulling the tendon to one side. For example via poor footwear, ankle joint hyper-mobility (excessive natural joint movement), or a Hip / Knee misalignment affecting the leg as a whole.
  • RSI – Extensive repetitive force or strain within a daily activity or one above the involved tendon’s normal condition. e.g. over-training or the individual performing training / exercise repeatedly above their current physical niveous.
  • Post-operative or local injury tissue response – e.g. repeated calf strain history or surgery to the same leg or other leg causing a change in how the individual loads the affected tendon.
  • Obesity – Long term body weight stress on the knees, ankles & Achilles tendon promote a change in the ‘line of force’ on the involved tendon, thereby, promoting adverse tissue responses.

Other risk factors include diabetes, stiff ankles, or having long term tight/weak calf muscles.

Risks of Extensive / Long Term Achilles Tendinopathy

  • Increasing pain & decreasing mobility / function
  • Tendon Rupture – Extensive development of Type III Collagen fibres within the Achilles tendon has been shown to be clearly present in tendon tear sites. The culmination of many micro-tears can lead to a partial tear or full tendon rupture. A significant tear or full rupture would require long-term treatment potentially involving surgery.
  • Plantar Fasciitis (inflammation / abnormal changes to the foot’s sole fascia (a broad sheet of connective type tissue containing collagen strands similar in relation to a tendon structure) – Some studies have concluded with indications that these two conditions can sometimes be closely related and potentially initiate each other.


There are variable conservative and surgical treatment options for Achilles tendinopathy. However, there has to date not been a gold standard type treatment defined because of the differing clinical results between various studies. This may be due to different studies being performed on varying patient groups & / or stages/types of Achilles tendinopathy In the future, new researches will be needed to fully appraise the effect of these treatment options.

However, in regards, to non-operative treatment formats, to date there are a few that display good track records when applied well:


  • Extra-Corporeal Shockwave Therapy (ESWT) – A relatively modern method of utilising vibration shockwaves to ‘destroy’ mis-grown fibres and enhance repair and replacement. To date, this treatment method displays a high success rate.
  • Eccentric loading program – Usually over a 12-15-week program. A systematic exercise method utilising accurate ‘reverse’ muscle activity to reorientate tendon fibre/function & reduce pain.
  • Taping techniques – Offloading the tendon & realigning ‘lines of force’.
  • Soft tissue treatments such as massage/friction massage/muscle energy techniques.
  • Ultra-sound – Controlled sound waves to change chemical processes within biological tissue.


  • Orthotic Assessment – Modern Podiatrists employ accurate videoed / computerised assessments of patients gait and mechanical alignment on the lower limbs to create bespoke orthotics such as shoe inserts to realign affected structures.
  • Night Splints – A more traditional method of gradually stretching the tendon and encouraging healthy tissue orientation.

General Advice

  • Do not start actively or passively stretching your Achilles religiously if you have had tendinopathy for more than approximately 6 weeks. Studies indicate that this condition does not immediately respond well to classic stretching if it is developing to a later stage.
  • Rest if your symptoms are being aggravated by a particular activity or sport (either during or after) then you should cease this activity for an advised period. The more you aggravate it the longer this condition will plague you!
  • Ice ONLY if the symptom area is hot & swollen otherwise do not.
  • Heat ONLY on the involved calf muscle and NOT on the tendon itself to relax the muscle and decrease muscle tension on the tendon.
  • Seek Professional Guidance from an appropriate health professional specialising in this type of condition such as a Physiotherapist, Podiatrist, Sports therapist, or ask your GP.
  • Beware of colloquial advice – i.e. Someone at the gym said… do this or do that… Your condition is unique to you. Someone else’s Achilles tendinopathy may be in a completely different stage or clinical condition.
  • Footwear – Supportive shoes or trainers with supported arches can help. Shock absorbing / slightly raised heels may also alleviate symptoms. Ensure that there is no pressure at the rear against the lower part of the tendon.
  • Tearing or ‘Crepitation’ Feelings – Usually accompanied by sharp pains within the calf/tendon itself should be assessed as soon as possible by an appropriate Health Care Professional.