Achilles tendinopathy
In this section we discuss the Achilles tendon anatomy, the pathology underlying overuse Achilles tendinopathy, factors that predispose to such injury, the clinical features of the condition and guidelines for imaging. The next section details the rehabilitation of these injuries.
The Achilles tendon, the thickest and strongest tendon in the human body,(9) is the combined tendon of the gastrocnemius and soleus muscles. The tiny plantaris muscle also inserts into the Achilles tendon. The tendon is surrounded by a paratenon (also known as peri-tendon/ paratendon), not a synovial sheath, which is continuous with the fascia of the muscle and the periosteum of the calcaneus.
Pathology and pathogenesis of Achilles tendinopathy
When operating on patients with chronic Achilles tendinopathy, the surgeon generally finds a degenerative lesion characterized by an intratendinous poorly demarcated dull-grayish discoloration of the tissue with a focal loss of normal fiber structure (Fig. 28.5).(1) A partial tear or rupture, defined as a macroscopic discontinuity involving a small proportion of the tendon cross-section (Fig. 28.6), is seen in about 20% of cases.
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The paratendinous structures are either normal or contain inflammatory edema or scarring. Importantly, when the symptomatic parts of such Achilles tendon tissue are examined under the light microscope, there is abnormal collagen fiber structure, poor healing response and absence of inflammation. This applies equally to areas of partial tear, which show hypervascularity (a response to tissue hypoxia) without signs of tissue repair.(1) This histopathological picture is called ‘tendinosis' and is identical in tendons with macroscopically evident partial tears and those without. These regions of tendon degeneration correspond with areas of increased signal on MRI and hypoechoic regions on ultrasound.(5) (10) |
| Factors that may predispose to Achilles tendinopathy
Injury to the Achilles tendon occurs when the load applied to the tendon, either in a single episode or, more often, over a period of time, exceeds the ability of the tendon to withstand that load. Factors that may predispose to Achilles tendon injury include: (6) (11-13)
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years of running
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increase in activity (mileage, speed, gradient)
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decrease in recovery time between training sessions
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change of surface
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change of footwear (e.g. lower heeled spike, shoe with heel tab)
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excessive pronation (increased load on gastrocnemius–soleus complex to resupinate the foot for toe-off) (Fig. 28.7)
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calf weakness
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poor muscle flexibility (e.g. tight gastrocne-mius)
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joint range of motion (restricted dorsiflexion)
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poor footwear (e.g. inadequate heel counter, increased lateral flaring, decreased forefoot flexibility) (Chapter 6).
Clinical features of tendinopathy
There are a variety of different clinical presenta-tions of Achilles tendinopathy. Patients can present with any combination of clinical fea-t u res and imaging appearances as listed in Table 28.2.
Guidelines for imaging in Achilles tendinopathy
Because of the various appearances of Achilles tendinopathy with imaging (Table 28.2) we recommend that the history and physical examination remain the keys to diagnosis. If there is doubt about the diagnosis or concern that the pain may be arising from other sites (e.g. associated bursae), ultrasound or MRI may be indicated. Until patients become familiar with the concept of tendinosis, imaging can help illustrate that the abnormality is one of collagen degeneration rather than inflammation. We suspect this may help with compliance but have no data to support this contention.
Fig. 28.7 Whipping action of the Achilles tendon produced by overpronation as described by Clement et al.
Table 28.2 Combination of clinical features and imaging findings on presentation with overuse Achilles tendinopathy (i.e. not a complete rupture)
| Clinical feature or imaging finding tendinopathy |
Variability in presentation with overuse Achilles |
| History |
| Onset of pain |
May be sudden, gradual but noticeable, or insidious |
| Severity of pain |
May range from a minor inconvenience to profound pain |
| Duration |
May range from days to years |
| Disability |
May be minimal, moderate or severe |
| Examination |
| Extent of swelling/crepitus |
Can range from being a major feature of the presentation to being absent |
| Extent of tenderness |
May range from being pinpoint to extending throughout several centimeters of the tendon |
| Presence of a tender nodule |
May or may not be present, and when present may vary in size from a square millimeter to 5 mm by 5 mm |
| Investigation |
| Ultrasound extent of hypoechogenicity |
Sonographic hypoechogenicity (representing fluid) can vary from absent to marked. It is possible to have a normal ultrasound scan with symptoms and signs of Achilles tendinopathy |
| Ultrasound discontinuity of tendon fibers |
Tendon fibers may appear intact or extensively damaged on ultrasonography. It is possible for a patient to have a completely normal ultrasound scan with marked clinical features of Achilles tendinopathy |
| MRI appearance |
The MRI appearance can vary from essentially normal to a marked increase in abnormal signal, best seen on T2-weighted sequences |
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