The Myth and Truth of Achilles Tendonitis

The Achilles tendon is the thickest and strongest tendon in the human body. It is located where the two heads of the gastrocnemius and one head of the Soleus come together to form a cord-like tendon called the triceps surae.  This musculo-tendinous unit crosses three joints and exerts meaner force on all three of them than a junkyard Cerberus. The tendon inserts into the middle part of the posterior surface of the calcaneus, a bursa being interposed between the tendon and the upper part of this bone. No other muscle group in the human body exerts such influence, making it the stuff of myths and Homer’s Legends. Doh! Not that Homer, but the one of Iliad and Odyssey fame.

Modern day myth starts right with the diagnosis. I feel like Sisyphus when people talk to me about Achilles Tendonitis. Most cases of injury in the back of a runner’s heel turn out to be Achilles tendonosis. There is no actual clinical inflammation in the tendon nor are inflammatory cells found in biopsy samples. Hence, tendonitis is a misnomer. Tendonosis is due to chronic degenerative changes in the tendon from repetitive microtrauma and tissue overload. Achilles Tendonitis does occur; however, I will be making orthotic devices for a Minotaur before the number of “it is” cases overtake the number of “osis” cases.

The etiology of this condition is complex and multi-factorial. It includes:
Gastrocnemius or soleus muscle fiber injury. Muscles fire basically in three ways and hence can be injured in three different ways. The shortening action of muscles is called concentric firing. You fire the Achilles complex concentrically when you raise your foot at the ankle on a step.

The breaking action of muscles is called eccentric firing. Many people are ‘Zeus lightning bolt shocked’ when I tell them that dysfunction/injury of this type is most common. The muscle fires to slow down the lengthening of the muscle. It is a decelerating or braking type action of the complex. The Achilles complex does this shortly after your heel makes contact with the ground during a running stride and does this for only the first half of that split second the foot is on the ground.

Postural is the third type of muscle firing.  It is the subconscious postural firing of this muscle group that keeps you from falling flat on your face while standing. A muscle can have injured eccentric abilities but not concentrically (or vice versa). The same relationship goes with postural versus the other two.

Structural weakness is common at any tissue change. Tendons are arranged in parallel fibrils. Any knick in the tendon can cause longitudinal tearing along these parallel fibril planes.
Lack of Flexibility can play a role in the early stages of this problem but rarely in the late stage. For this reason, stretching makes a poor universal treatment. Many later stage tendinosis patients are made worse by stretching. 

Sometimes tightness is not in the muscle fibers but in the golgi bodies and other parts of the tension monitoring systems within the musculo-tendinous unit. These problems will not respond to traditional stretching and require a different type of exercise.

Bad Shoes-old shoes, defective shoes, and models that are not a match for your foot type can all put abnormal levels of stress on the tendon.

Bad foot biomechanics– Surprisingly, this is a rare cause of tendinosis in my clinical experience. It occurs when there’s too much of a certain motion in a foot joint, or if the right amount of motion occurs but at the wrong time. Fortunately, it is easy to fix when this Pegasus of a different color does occur with use of a custom foot orthotic device.

The shape of your heel bone- a prominent bump on the back of the heel bone leads to more wear and tear of the tendon. Poorly shaped subtalar facets lead to the biomechanical stresses mentioned above.

The width of your Achilles tendon– Dr. Richard Schuster analyzed the data of over 10,000 of his athlete patients and found a statistical correlation between the width of the tendon and incidence of its injury. He found that thin tendons are more prone to injury.
Nutritional deficiency- Adequate amounts of Vitamin C are critical to tendon healing. Other deficiencies are more individual and open the doors to Hades with any further generalized discussion.

Loss of ankle proprioception- Proprioception is the ability to know the location and position of a body part without actually looking at it. Loss of this ability has been implicated in all kinds of running injuries. This one is no exception. 

Drug side effects– History of steroid injections into the tendon or general use of certain types of oral antibiotics ( e.g. fluoroquinolones) It is well known that corticosteriod injections into the tendon may lead to tendon weakness or even rupture. Few people know that certain types of antibiotics can be a chemical Trojan horse for tendon injury.

Age– By the time we hit our mid 30’s, tendon tissue slowly starts to loose it resiliency. The number of mitochondria found in our cells reduce in number. Training effect and stress adaptation are slower to respond.  This is a sad fact of life as to why degenerative conditions become more common in the second half of life.  Age just has a way of making Icarus fly too close to the sun.

Illness– Diabetes, gout, and many other chronic diseases can and do play a role in this injury.
Improper amount of stress on the body part before adaptation. This has been called Overuse Syndrome. I hate that term as it leads to myths about exercise in general. The Achilles is stressed by running too fast, too soon.  However, it would be a myth to think that Hermes-type speed is the only danger. It is also caused by running too slow. Too much hill training (up or down) can also cause adaptation overload.

Low back injury– sometimes the heel hurts because of injury or function change initiated elsewhere. In my clinical experience, injury to the 5th lumbar, 1st and 2nd sacral vertebrae, are the most common sites to trigger the tendinosis cascade.

Treatment is as diverse and varied as the causes of this malady. Each person needs a unique treatment plan.
Rest becomes a four letter word to the runner when it comes to injuries…whoops, it really is a four letter word!  Nevertheless, rest does play a role in the healing of these problems in most cases. The length of time depends upon the severity of the injury. Rest can be complete—such as with a below knee splint or it can be done with partial rest. I prefer partial rest in most cases.

My favorite method is to off-load the tendon with a carefully applied special type of tape that mimics tendon function. This allows the patient to continue some running, while avoiding muscle atrophy and increasing blood flow and anabolic processes that exercise stimulates so well. Partial rest can be a real win-win situation.

Eccentric strengthening exercises come the closest to being a universal conservative treatment for the tendinosis condition. However, at the risk of being a repetitive Sirens’ song, no long term treatment plan will be highly effective unless you address as many underlying cause and risk factors as you can.

Robert “Doc” Chasen practices Podiatry and puns (not necessarily in that order) in Weymouth, MA. In his youthful Herculean years, he had a 24:39 5-mile and 30:26 10K to his credit. As a master, he won a silver team medal at the WAVA World Masters Cross Country Championships. He also was a 3-time New England age group Mountain Running champion.

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