Achilles tendon injuries comprise a large spectrum of pathology. Generally, when we speak about Achilles tendon pathology, we first determine if the tendon is ruptured or not ruptured. If the tendon is not ruptured, it is further classified as to whether the problem exists at the attachment site of the Achilles on the calcaneus, in which case we call it “insertional,” or if symptoms exist proximal to this area, or “noninsertional.” For the purposes of this chapter, the pathology has been separated into noninsertional tendinosis, insertional tendonitis, and rupture. While these may seem somewhat arbitrary divisions in similar disease processes, clinical practice among foot and ankle surgeons has necessitated this separation, since the aforementioned diagnoses require unique diagnostic and treatment algorithms to achieve resolution.

Noninsertional tendinosis is when there is actual intratendinous degeneration of the Achilles tendon proximal to its attachment to the calcaneus. The tendon is typically swollen, and the onset of symptoms is insidious and located within the midsubstance of the tendon. It is not called “tendonitis” because histologic evaluation reveals no true inflammatory component. Instead, a fibromyxoid degenerative tissue with a high water content replaces normal tendon.1 Unlike tendinosis, insertional tendonitis is an inflammatory condition that occurs at, and around, the Achilles tendon insertion into the calcaneus.

The noninflammatory degenerative process seen in tendinosis is likely due to the fact that the tendon itself has sparse cellularity and vascularity, both of which impair the inflammatory process. As a result, the tendon becomes thicker, softer, and yellowish, owing to an accumulation of mucinoid material within the tendon.2 Degeneration within the tendon itself is often insidious and asymptomatic. It is thought to occur as a result of repetitive microtrauma, aging, or a combination of both.2 The presentation is the insidious onset of swelling and pain at the midportion of the Achilles tendon typically 4 cm proximal to the distal insertion of the Achilles.

Insertional tendinitis is a true inflammatory process within the insertion of the Achilles. It is often associated with a Haglund deformity (bone spur anterior to the insertion site) and is often associated with hill running and interval workouts. 3 Training errors such as improper stretching prior to exertion or excessive increases in exercise intensity can quickly exacerbate this condition.1 Insertional tendonitis presents with posterior heel pain thought to be due to bony impingement from the calcaneus, local bursitis, or both.

Achilles tendon rupture is the most common tendinous rupture in the lower extremity, has a peak incidence in the third to fifth decades, and occurs five times more often in males. It is classically described by middle-aged athletes (weekend warriors) who have experienced a sudden pain with an audible “pop” in the back of their heels. Many report the sensation of being hit, when in fact they have not been.

Pain is the cardinal symptom of Achilles tendinopathy. In the early phase of insertional and noninsertional tendinopathy, patients may complain primarily of pain following strenuous exercise and, if progressive, can develop pain that accompanies routine activities. For athletes, the pain can be disabling enough to curtail training regimens.

On physical examination, findings can vary depending on how advanced the process is. Decreased ankle dorsiflexion and hamstring tightness are commonly found in patients with Achilles pathology.4 Clinically, it is important to note the contour of the tendon, any areas of widening, and the presence or absence of nodules. Most runners present with a gradual evolution of symptoms, including pain and swelling approximately 4 cm proximal to the calcaneal insertion. Differentiating between the conditions that cause posterior heel pain can be difficult and can perhaps be thought of as a spectrum of a single disease process. However, insertional tendinitis requires that patients have tenderness at the bonetendon interface, and examination will reveal point-specific pain at the insertional interface, often posterolaterally. There is also limited dorsiflexion. If the tendinitis becomes chronic in nature, the tendon can also become palpably thickened. The pre-Achilles bursa can also be inflamed causing a pump bump (see Chapter 25 for full discussion).