The Achilles tendon is the largest tendon in the human body. It forms from the confluence of the gastrocnemius and soleus muscle tendons, known as the triceps surea, which is innervated by the sacral spinal nerve 1 via the sciatic nerve 5 to 6 cm proximal to its insertion onto the posterior aspect of the calcaneal tuberosity.⁶ The tendon is enveloped in a thin vascularized layer called the paratenon, which is perfused by branches from the posterior tibial and peroneal arteries. The tendon itself, however, is largely avascular, with its midportion having the least perfusion.^7,8 This lack of vascular perfusion leaves the Achilles tendon highly susceptible to injury and poorly able to heal.⁷ 

The tendon transmits the force generated from the contraction of the triceps surae muscles to the foot through the ankle joint. When standing, the soleus muscle, acting in concert with the tibialis anterior muscle, stabilizes the tibia. During locomotion, the triceps surae serves 2 functions: to eccentrically contract to control the forward progression of the tibia during the stance phase of gait, and to concentrically contract against the fixed forefoot during the terminal stance through toe-off phases of gait, thereby creating the propulsive force necessary for walking, running, and jumping. 

Most Achilles tendon disorders can be diagnosed on a clinical basis. A thorough problem-focused history should include details of the inciting event, the presence and duration of prodromal symptoms, the patients’ customary daily activities, and the frequency and level of athletic activity, if applicable. Previous lower extremity trauma should also be noted. Given the well-described associations with Achilles tendon disorders, medical history taking should specifically address the coexistence of autoimmune disease; plantar fasciitis; 

metatarsalgia; plantar skin problems, such as callosities or ulcerations; the rate and amount of any weight gained, if applicable; previous treatments, such as injection of corticosteroids into the tendon; frequency and duration of systemic fluoroquinolone antibiotics, if applicable; and smoking history.^9-11 

Patients with acute ruptures typically report that the sudden onset of posterior heel pain occurred during high-impact activity.^1,9 Chronic conditions develop more insidiously, often after an abrupt increase in activity level or training intensity, particularly among middle-aged persons or seemingly without provocation among sedentary and elderly persons.^12,13 

Given the broad spectrum of disorders that may present similarly to Achilles tendon disorders, a detailed musculoskeletal examination of both lower extremities should always be performed simultaneously. The skin over the heel cord should be inspected for swelling, ecchymosis, or bony prominences. The entire length of the tendon should then be palpated to feel for fullness, irregularity, gapping, or tenderness. Active and passive ankle ranges of motion should be assessed and muscle strength testing performed. Gait disturbances should be observed with the patient walking barefoot. The examination should be broadened to include the upper extremities and autonomic nervous systems as needed. The Table summarizes the distinguishing patient history and physical examination findings among the various Achilles tendon disorders. 

A logical role exists for OMT during the evaluation for Achilles tendon disorder. By reducing or eliminating the effects of somatic dysfunction on the patient’s symptoms, the physician may obtain a clearer assessment of the patient’s problem. 

After a thorough clinical evaluation has ruled out the Achilles tendon as the primary source of pain, a more inclusive differential diagnosis should be considered (Figure 1). The differential diagnosis can be classified into vascular, neurogenic, myotendinous, and osseous origins. 

The initial evaluation of Achilles tendon disorders does not often require the use of diagnostic imaging. However, magnetic resonance imaging, ultrasonography, and radiographic imaging may be necessary in the presence of equivocal examination findings, to narrow the differential diagnosis, or for surgical planning. 

Most Achilles tendon disorders can be successfully managed conservatively. Because older and sedentary patients with multiple comorbitities have higher rates of postoperative complications,^20,26 conservative management should 

be the primary consideration in these patients. Poor surgical candidates or those with low functional demand should also be treated with conservative measures.^27,28 Achilles tendon overuse injuries are initially managed with rest, ice, activity modification, and symptomatic analgesia (eg, nonsteroidal anti-inflammatory drugs).^6,12,17,23 

Acute ruptures may be managed initially with an Achilles walking boot beginning at 20° of ankle-plantar flexion. The ankle is repositioned back to neutral in a stepwise fashion at 6 to 8 weeks.²⁹ Full weight bearing in this orthosis may resume after 2 to 3 weeks. 

Long-term use of a brace or an ankle-foot orthosis may be needed to provide sufficient functional stability.³⁰ Tendinosis (both insertional and noninsertional) and paratenonitis may respond to foot orthoses, such as cushioned heel lifts, which function by correcting overpronation and elevating the heel to decrease tendon irritation, and stretching.¹⁷ If symptoms do not improve, a physical therapy regimen focusing on eccentric stretching exercises may be considered. 

The utility of OMT in managing Achilles tendon disorders is understudied. However, the counterstrain technique has been shown to alleviate excess tension placed on the Achilles tendon, thereby decreasing nociceptor activity.³¹ This method involves placing the Achilles tendon in the position of least resistance by having the patient lay prone while passively flexing the knee and plantar flexing the foot and ankle (Figure 2). This position should be maintained for approximately 90 seconds while monitoring the tenderpoint, most commonly located along the tendon or at its point of insertion. The foot should then be placed in a neutral position and reassessed.³¹ 

To counteract the failed healing response to repetitive subfailure loading, eccentric stretching has been proposed to facilitate collagen fiber cross-linking and promote tendon remodeling.^13,32 This method is especially effective in cases of paratenonitis and noninsertional Achilles tendinosis.^6,13,18 Further investigation is necessary into the use of modified eccentric exercises in patients with insertional tendinosis, as these exercises seem to be beneficial in 32% of cases.¹² 

As soon as possible after the initial injury, physical therapy should be started. The therapist should initially concentrate on isometric strengthening and eventually progress to range of motion exercises for the ankle and concentric triceps surae strengthening.^29,33 

Symptomatic analgesia is typically managed with nonsteroidal anti-inflammatory drugs.^6,12,17,23 Short-term anticoagulation with low-dose aspirin can be considered to prevent the formation of deep vein thrombosis.³⁴ Injections of agents, such as isotonic sodium chloride solution, local anesthetic, platelet rich plasma, and corticosteroid preparations in and around the Achilles tendon are controversial. None of these treatments has been shown to have medium- to long-term efficacy. However, clear agreement exists in the literature that corticosteroid injections should be avoided because of the increased risk of tendon rupture.^12,13,18 The short-term efficacy of bupivacaine or saline in conjunction with physical therapy to break up adhesions is best supported in cases of paratenonitis.⁶ 

Chronic Achilles tendon ruptures often require surgical reconstruction because of persistent impairment associated with nonoperative management. Referral to a specialist is indicated for acute tears in younger, active individuals with 

higher functional demands, when a chronic tear is suspected, or at any time when Achilles overuse symptoms are progressive, persist, or recur despite approximately 6 months of conservative management. 

Achilles tendon injuries are among the most common musculoskeletal injuries.⁶ The diagnosis of these injuries is most commonly based on a thorough history and physical examination and may require imaging in certain cases. Acute tendon ruptures should always be ruled out at initial presentation. Risk factors include autoimmune disease, plantar fasciitis, obesity, fluoroquinolone use, local corticosteroid injection, and tobacco use. Conservative management modalities are successful in most cases of Achilles tendon disorders.⁶ Whereas Achilles overuse injuries are primarily managed with rest, ice, activity modification, and nonsteroidal anti-inflammatory drugs, other disorders may benefit from orthoses, OMT, eccentric stretching exercises, physical therapy, medications, and various injections. Surgical intervention should be reserved for acute tears in younger patients, active patients, patients in whom a chronic tear is suspected, or those with overuse symptoms recalcitrant to conservative management.