Foot overuse injuries are caused by repetitive stress over time. They have a gradual onset and progressive nature. Signs of inflammation (eg, swelling, redness, pain) can occur in the acute phase. The etiology may be intrinsic, extrinsic, or a combination of the two. Intrinsic factors can include patient age, sex, genetic predisposition, body weight, and blood supply. Extrinsic factors can include training errors, environmental conditions, equipment malfunction, and shoes. Common causes of foot pain and overuse injury include Achilles tendinopathy, Morton neuroma, and plantar fasciitis. The history should include onset, duration, and progression of symptoms; new physical activity or increased intensity of activity; and aggravating and relieving factors. The physical examination should include assessment of range of motion, adjacent structures, and provocative maneuvers. Laboratory testing and imaging are not required, but imaging can be used to rule out other conditions or when surgical intervention is being considered. Conservative management, including analgesia, nonsteroidal anti-inflammatory drugs, rest, activity modification, and physical therapy, is the mainstay of treatment. Referral to podiatry, sports medicine, or orthopedics can be considered in difficult cases. Surgical intervention may be necessary if conservative management does not bring relief.
Case 4. AZ is a 46-year-old patient with obesity and gastroesophageal reflux disease. He comes to your office with a 3-month history of posterior heel pain, especially when walking. The physical examination reveals no erythema, but there is tenderness at the insertion of the Achilles tendon. AZ says he works as a courier 5 days/week and cannot afford to take time off. He asks you for advice about how to manage his foot pain, and wonders if his work boots may be contributing to the problem.
Achilles Tendinopathy
EPIDEMIOLOGY, PATHOPHYSIOLOGY, AND ANATOMY
The Achilles tendon is the largest tendon in the human body and can withstand loads several times a person’s body weight. Despite its strength, the Achilles tendon is the most injured tendon.1 The correct pathophysiologic term for the degeneration of a tendon is tendinosis but is commonly referred to as tendinitis or tendonitis.2,3 The consensus among researchers is that the term tendinopathy should be used to refer to injury of the tendon due to overuse. Tendinopathy is more accurate because histologic evaluation of these injuries demonstrates an absence of inflammatory cells and a disorganized cellular response with degeneration of intratendinous structures.
The highest incidence of Achilles tendinopathy is reported in those ages 30 to 55 years.4 Achilles tendon injuries occur due to intrinsic and extrinsic factors that result in repeated injury or mechanical strain, and lead to tendon degeneration.2,4 Acute injuries tend to be predominantly due to extrinsic factors, whereas chronic injuries tend to be due to a combination of factors.2 Intrinsic factors include age, sex, body weight, tendon temperature, systemic diseases, muscle strength, flexibility, previous injuries, genetic predisposition, and blood supply.4 Extrinsic factors include drugs (eg, fluoroquinolone antibiotics, corticosteroids), overuse, training errors, environmental conditions, shoes, and equipment surfaces.2,4
The Achilles tendon, also referred to as the calcaneal tendon or triceps surae, is composed of collagen and elastin arranged in a wavy configuration.2,3 It lacks a true synovial sheath but is surrounded by a connective tissue layer called the paratenon that allows for gliding with elongation and shortening. The Achilles tendon consists of an aponeurosis created by the two tendons of the gastrocnemius muscle bellies and the single soleus tendon. The loads generated by these muscles are transmitted through the Achilles tendon to the calcaneus. The average Achilles tendon length is 15 to 26 cm in adults. It has a hypovascular area (referred to as the watershed zone) located 2 to 6 cm proximal to its insertion on the calcaneus. This zone is particularly vulnerable to injury due to substantially decreased blood flow, and is the most common site of rupture.5
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