This powerful tendon, sometimes called the heel cord, attaches the two major calf muscles (gastrocnemius and soleus) to the calcaneum (heel bone) and transmits the propulsive forces needed for walking, running, and jumping. The tendon is composed of spirals of collagen that are wrapped into bundles forming a thick cord that is both strong and able to stretch.

Because of the property of viscoelasticity, a sudden rapid muscle contraction will find the tendon relatively stiff while slower contractions allow greater stretch. With repeated stretching, the tendon becomes more flexible. Although this applies to all ages, maximum flexibility does slowly decreases with increasing age. The frequency of Achilles tendon injuries appears to be increasing, with about 8 percent of top-level runners having some Achilles problem each year.

Rupture of the achilles tendon - The ability of tendons to stretch and become more elastic during use is the rationale for warming up before participating in sports. The typical Achilles tendon rupture happens when a relatively untrained middle-aged athlete plays a sport such as tennis and makes a sudden forward movement.

The rapid stretch of a relatively stiff tendon can cause it to rupture and the athlete feels sudden pain, as if kicked on the back of the leg. He or she is unable to walk or stand on tiptoes and may hear a pop as the tendon snaps. The midtendon rupture of the Achilles is unusual for a tendon.

Like most tendons the Achilles is nearly twice as strong as the muscles it joins. Because of this, tendons normally tear in the area where they join onto their muscle since this is the weakest part. Therefore, for the midtendon to rupture there is usually a preexisting abnormality that has weakened it.

The tendon may have been damaged by previous trauma, TENDINITIS, long-term corticosteroid use, local steroid injections into or around the tendon, and other chronic medical illnesses such as kidney failure. A few cases of tendon rupture have been described in people taking quinolone antibiotics, for example ofloxacin.

The treatment of a ruptured Achilles tendon can be either conservative, with the leg immobilized in a plaster cast for about six weeks, or surgical, with open repair of the tendon again followed by immobilization for about six weeks.

Surgical repair decreases the risk that the tendon will rupture again from 10 percent to 2 percent. However, surgery may not always be the best option, particularly if the person has other medical problems or is not athletic and is therefore less likely to stress the tendon in the future.

Other conditions affecting the achilles tendon - Inflammation of the tendon at the point where it joins bone is called enthesitis and is common in ANKYLOSING SPONDYLITIS and REITER’S SYNDROME. Treatment includes an orthotic shoe insert or a special shoe designed to raise the heel, rest, ice, local corticosteroid injection, and NSAIDs followed by rehabilitation stretches.

Inflammation of the Achilles tendon (tendinitis) occurs particularly in long-distance runners and athletes involved in jumping sports or in those using unsuitable footwear or having a biomechanical problem. All these will place unusual or abnormal stresses on the tendon. Tendinitis causes pain in the area around the tendon, particularly when it is stretched during activities such as walking or running.

The tendon is often visibly enlarged, warm, and very tender to the touch. It can be very difficult to decide whether the inflammation is mostly in the tendon or around it (peritendinitis), and both are often present. Sometimes the tendinitis occurs because of a partial tendon rupture, and ultrasound scanning is excellent at showing this.

The treatment of Achilles tendinitis is similar to that of enthesitis except that local steroid injections near the middle of the tendon are avoided because they may weaken the tendon and increase the chance that it will rupture. Surgery to remove surrounding inflamed tissue and chalky material from within the tendon where it has degenerated is performed if conservative treatment fails.

This is successful in 80 percent of competitive athletes. If the person’s shoes or biomechanics of walking or running are faulty, the condition may be corrected with appropriate shoes. Bursae between the skin and tendon and between the tendon and underlying bone can become inflamed and cause symptoms similar to tendinitis. The treatment of bursitis around the Achilles tendon is similar to that of tendinitis.