The Achilles tendon is the largest and strongest tendon in the human body, but is simultaneously a vulnerable link in the locomotion chain. (1) The tendons’ structural integrity is relentlessly confronted by functional demands that can be up to 12 ½ times body weight while running. (2)

The Achilles tendon may be acutely strained or ruptured as the result of an excessive stretch or eccentric force. Consistent with other types of acute strains, Achilles tendon injuries may occur when the musculotendinous unit transitions from eccentric deceleration to concentric propulsion. This happens during the “mid-stance” phase of gait. (3) Strains occur when collagen fibers are stretched by more than 4%. Ruptures occur when stretch exceeds 8%. (4,5)

Unlike acute injuries that cause inflammation, tendinopathy is characterized by repeated overloading, microtearing, failed healing, and subsequent tendon degeneration. (3,4,6,7) The process begins with collagen fiber disruption and ends in a disorganized healing process that fails to regenerate a “normal” tendon. Failed healing is blamed on a hyperplastic, but ineffective, microvascular system. (8,9) Structural changes in asymptomatic tendons have been found in almost 25% of runners. The presence of these structural changes was associated with increased development of Achilles and patellar tendon pain within one year. (117)

An appreciation of gait mechanics is relevant to understanding Achilles tendon injuries. During normal gait, the foot approaches the ground with 3-4 degrees of supination, allowing ground contact to occur on the lateral portion of the calcaneus (heel). As a shock-absorbing mechanism, the foot initially relaxes into subtalar pronation. At mid-stance, the foot converts into a rigid lever and begins to supinate in anticipation of propulsion. Tibial external rotation accompanies ankle supination. Inefficient conversion from shock absorber to rigid lever results in hyperpronation which stresses the medial calcaneotendinous attachment of the Achilles tendon. (10)

Injuries to the Achilles tendon may be classified as “insertional” or “non-insertional.” Insertional tendinopathy, as its name implies, describes damage to tendon fibers at their insertion on the posterior calcaneus. This process may result in calcification and bony exostosis producing a prominent enlargement of the posterior calcaneus, also called a “Haglund deformity” or “pump bump.” Non-insertional Achilles tendinitis most commonly involves the vulnerable “watershed area”, 2-6 cm proximal to the calcaneal insertion. (11) This region of the tendon has a smaller cross-sectional area, is relatively hypovascular, and is subject to a repetitive “wringing” motion during supination/ pronation. This susceptible mid-section is the most common site for degeneration and rupture. (12,13)

Achilles tendon injuries affect between 250,000 and 1 million people per year in the United States. (14,15) Most are middle-aged males in their third or fourth decade of life. (14,16) Runners with Achilles tendinopathy had lower activity levels, [i.e. deconditioned athletes] exhibited lower soleus strength, and BMI, and leg curl strength which explains condition severity. (119) Interestingly, Achilles tendon injuries occur more frequently on the left side. (16) Injury rates are highest in the spring months and lowest in the fall. (93) Patients who have suffered prior Achilles tendon rupture are at significantly higher risk for contralateral tendon rupture. (17)

Two-thirds of all Achilles tendon injuries involve athletes. (18) Runners are up to 10 times more likely to suffer Achilles tendon injuries compared to age-matched controls. (18) One in twenty recreational runners will develop Achilles tendinopathy. (101) The Achilles is the most common site of tendinopathy in runners. (77) Athletes are at greater risk during speed training or sprinting. (19) Runners who assume a midfoot or forefoot strike pattern may be at even greater risk of injury. (20) Compression socks are a known predisposing factor. (101) Not surprisingly, a higher risk has been identified in other sports that involve running or jumping. The estimated incidence of Achilles tendinopathy is: running sports, 53%; soccer, 11%; dance, 9%; gymnastics, 5%; racquet sports, 2%; football, 1%. (14,21)

Extrinsic risk factors for Achilles injury include improper warm up, overtraining, cold weather training, running on hard surfaces, excessive stair or hill climbing, improper arch support/ footwear, poor conditioning and abruptly returning to activity after a period of inactivity. (19,22-26,94) Wearing high-heeled shoes may lead to shortening of the gastrocnemius/soleus, predisposing women to Achilles tendinopathy. (27) Intrinsic factors include, prior lower limb fracture, hyperpronation, pes planus, cavus foot, gastrocnemius/soleus inflexibility or weakness, limited ankle dorsiflexion, and limited subtalar motion. (14,22-26,94,96) Systemic risk factors include diabetes, hypertension, inflammatory arthropathy, gout, and the use of corticosteroids or fluoroquinolone antibiotics, particularly Levofloxacin. (28,81,84,94,114,121) Obese patients carry a 4-6 fold higher risk of developing Achilles tendinopathy. (105)

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What we do in our office to help this condition:

1. Perform a detailed exam, assessing the alignment of the spine, pelvis, hips, knees, ankles, and small bones of the foot. Improper alignment in any of these areas may be detrimentally affecting the function of the Achilles, and compromising its ability to function normally.

2. As indicated, adjust areas of subluxations (misalignments), restoring proper alignment and nerve system function, which facilitates healing. It is common to find subluxated bones in the feet when someone is experiencing Achilles tendinopathy.

3. Perform laser therapy which penetrates to the cellular level of the soft tissues of the Achilles tendon. This promotes better oxygen and nutrients to the tissue, which can relieve pain and facilitate the healing process.

4. Conduct an electronic foot scan to see if the integrity of the foot’s arches have been compromised. If so, custom arch supports (orthotics) would be of benefit and can be prescribed.

5. Prescribe stretches and exercises in conjunction with chiropractic care to strengthen the soft tissues around the Achilles.