Definition

Degeneration and haphazard proliferation of tenocytes , disturbance of the pattern of matrix, collagen fibers and diameter of the collagen Fibers within the tendon. The diseased area of the Achilles tendon is in most cases a consequence of a chronic overuse or a failed healing response after an injury of the tendon. The result is usually a painful thickening of the achillestendon and its -sheet in the midportion of the tendon.

Causes
Sometimes the midportion achillestendinopathy is associated in rheumatoid disease e.g. with ankylosing spondylosis.
Chronic overuse and wrong training habits in amateur athlets, especially runners is by far the most frequent cause.
Overweight or biomechanical failure of the whole extremity or just the ankle (e.g. in varus position of the heel) can cause achillestendinopathy.
A short gastroc- soleus complex can also result in Achilles tendinopathy.

Symptoms
Painful swelling of the tendon and its tendon sheet with initial pain when used,pain ful nodules in the tendon or the tendonsheet, crepitation in the diseased area of the tendon. Highly painful squeeze test of the tendon.
Typically there is a painful morning stiffness- only in the acute phase the pain persists also in rest.

Diagnosis
Inspection and clinical examination is the first step- the squeeze test and functional testing is in most cases significant.
X- ray should be performed only if a sclerosis of the tendon or an underlying deformity of the limb  is suspected.
Ultrasound is a very helpful tool to diagnose and control the tendon and its tendonsheet.
The most sensitive exame is the MRI with perfect discrimination for intratendinous and peritendinous disorders.

Treatment

Following the general rule the primary treatment should be non-surgical.

a) Conservative treatment:

From recent studies we know that the midportion Achilles tendinopathy is a good responder to conservative treatment ( 60-70%).
The most effective therapy is proven to be eccentric training.
Other conservative treatment options are cryotherapy, low energy shockwave therapy, therapeutic ultrasound and friction massage.
There is incidence that lasertherapy and also acupuncture are helpful in combination with eccentric training.
Radiation therapy with a maximal total Amount of 3 Gy shows a high success rate of about 75 – 80% in literature.
Recent studies show success also after high volume peritendinous injections with the use of different agents, also peritendinous
injections of hyaluric acid or Platelet Rich Plasma seems to reduce the pain and swelling of the diseased area.
External or oral use of nonsteroidal drugs is proven to reduce the inflammatory response of the tendon.

b) Surgical treatment:

If conservative treatment is performed for a minimum period of 6 months and has failed to improve the symptoms significantly, surgical intervention is recommended. In 30- 40% of the patients with midportion tendinopathy surgery is necessary.
There is a high successrate in literature for surgical interventions- nevertheless there are only few highclass studies about the different interventions. Surgical options range from simple percutaneous tenotomy ( evt. ultrasound guided) to minimalinvasiv stripping of the tendon and up to open procedures. In open interventions the aim is to remove necrotic tissue out of the tendon with reduction of the increased diameter of the tendon, removal of scars and fibrotic changes of the paratenon and the tendonsheet. Multiple longitudinal incisions are used to remove mucoid or necrotic tissue out of the tendon and are thought to initiate a well ordered neoangiogenesis around the Achilles tendon. If resection of 50% of the diameter of the tendon or even more was performed an augmentation of the tendon is necessary to restore the biomechanical function. Usually the Flexor hallucis longus tendon from the great toe is used for this augmentation.

Postoperative therapy

The key point in rehabilitation after surgery is early motion and avoiding overload of the tendon. For the first 2 weeks after operation in most cases a light, removable cast in 20% flexion of the ankle is used. After this period the healing of the wound usually is finished. The patients may start active and also passive motion  and start to put load on their leg with a removable walker in limited equinus position which is changed every 2 weeks until a normal position of the ankle is reached. This period usually takes about 6- 8 weeks.
After that the patients start to walk in shoes with a mild heel elevation and continue physiotherapy for approximately 6 more weeks.