Lower Leg Injuries: Achilles Tendonitis, Shin Splints, Compartment Syndromes

Injuries to the tendons of the leg account for almost 25 percent of all of the injuries that affect running athletes. They are also difficult to treat because of the length of time needed for recovery. While there are many tendons in the lower leg that affect the function of the foot, there are three main ones involved in most problems. The Achilles tendon is the most frequently injured, followed by the posterior and then anterior tibial muscles and their tendons. The latter two are often termed "shin splints" muscles and can be very disabling.

Anatomy
All tendons are made up of closely-packed, white, fibrous tissue. The tendon is very strong and quite resistant to tension. In fact, tendon is so strong that bones or muscles usually are injured before a tendon tears. A common example of this is when a piece of bone is actually pulled away from the rest of the bone where the tendon is attached, rather than the tendon tearing and leaving the bone intact. Tendons are surrounded by a covering known as a sheath or paratenon, depending on the location of the tendon. The sheath is a tube in which the tendon can glide. A muscle is very elastic and pulls on the tendon. The tendon is quite inelastic. This muscle-tendon complex is what causes the bone to move.

Tendon Repair
If a tendon is injured, the defect in the tendon is repaired from the tendon covering the surrounding fatty tissue rather than just the tendon itself. Interestingly, the tendons reparative process is greatest prior to age 30. This is because the tendon has not yet lost its primary blood supply. After age 30, this is basically lost and the tendon's ability to heal itself is lessened. Ten don repair is best when the swelling of the injury is reduced in the first 48 hours, decreased stress is placed on the tendon in the first three weeks, and when an adequate blood supply is available.

If a tendon is allowed to heal properly, it almost always will repair itself and be strong. However, most times the pain, Mother Nature's warning signal, is not intense enough and the athlete continues his or her activity. This can lead to scar ring, swelling, decreased range of motion, and chronic disability. While a tendon is healing, it is always slightly enlarged and swollen. If the healing is complete, it usually will shrink back to its original size. To judge the amount of inflammation, it is a good idea to compare the thickness on the injured side to the unaffected side.

Types of Injury
There are three basic types of injury to the ten don. The first is Tendonitis. This is an inflammation of the tendon. Second is a partial rupture, which is a tear in the fibers of the tendon structure itself, and the third is a complete rupture. These can also be classified as first, second, or third degree tendon injuries. Obviously, the greater the extent of the injury, the longer it takes to completely recover. To facilitate repair of a tendon when injured, apply ice for the first 48 hours. Rest is necessary. This eliminates the stretching of the tendon fibers. Tendonitis can often best be treated by immobilization. Increasing the blood supply through physical therapy modalities such as whirlpool, ultrasound, diathermy or massage is very effective. It is very important to stress and exercise the tendon after the first stages of repair. Muscle activity and stress on the tendon helps in the reorientation of the tendon fibers, and allows them to line up properly. Exercise, using pain to tolerance, is necessary for complete repairs.

Achilles Tendon Injuries
Achilles tendon injuries represent the most common of the tendon injuries of the lower leg. In a study by Clement et al, training errors were identified as a primary cause of 75 percent of Achilles injuries. These training errors included decreased flexibility of the calf muscles, a sudden increase in training mileage, a severe competitive or training session, such as a marathon or 10K race, a sudden increase in training intensity, hill running, training after an extended period of inactivity, and running on uneven or slippery surfaces.

Most significantly, over half of the injuries to the Achilles tendon are from overpronation or abnormal inrolling of the foot. The primary function of the Achilles tendon is to provide stability to the outside of the foot during gait. If the foot is unstable, it affects the tendon and can cause it to become inflamed or even tear. Slow motion, high-speed film studies have demonstrated that excessive proration causes the Achilles tendon to produce a whipping action. This may cause microtears in the tendon and cause inflammation to occur.

In another study, it was shown this whipping action of the Achilles tendon affects the blood supply to the tendon six centimeters above where it attaches to the heel. This wringing out action of the blood vessels is what decreases the blood supply. The significance of this is that this area is the most common site of total rupture of the Achilles tendon. The area where the calf muscles and tendon meet (myotendonis junction) is another area of injury. Although this is higher up than most injuries to the tendon, the mechanisms are the same.

First degree Tendonitis frequently responds to conservative care as previously outlined. Once there is decreased pain, normal activities can be resumed. However, overstretching the Achilles tendon while it is repairing, can result in an incomplete (second degree) or complete (third degree) rupture.

Treatment
Treatment of Achilles Tendonitis is threefold: rehabilitation of the calf muscles and tendon, control of the inflammation and pain, and control of the abnormal biomechanics or overpronation.

Wall leans are used to provide flexibility. Face the wall at arm's length, then lean toward the wall without lifting the heel off the ground. This should be done one leg at a time with the knee straight, then flexed slightly to affect all of the calf muscles.

Toe raises are for strength. They are performed with the heel hanging over the edge of a stair, and moving the ankle up and down. This should be done in sets of ten and without a bouncing action.

Control of inflammation and pain is best achieved by using ice massage, physical therapy, or oral anti-inflammatories. A comment must be made about steroids. Steroid injections reduce the inflammatory process, thus reducing pain and swelling. However, steroids may delay the normal reparative process so that their use with a Tendonitis or mild rupture can produce further damage or even complete rupture. I am not in favor of using steroids for Achilles Tendonitis or any other tendon injury. One exception to this is chronic problems where conservative care has not been satisfactory and surgery may be the only recourse. Even so, injections must be used sparingly. Rupture of tendons has been reported and well documented in athletes following steroid injections.

Control of abnormal biomechanics or overpronation is best treated with orthotics. These devices control the function of the foot, can accommodate for leg-length differences, leg rotation, and absorb shock, thereby controlling the factors which cause the Tendonitis. There are two important features to look for in running shoes. The first is adequate flexibility in the forefoot. Lack of flexibility puts undue stress on the Achilles tendon. The second important feature to look for is the heel height. The heel should be between 12 and 15 millimeters in height, and should be in all athletic and casual shoes. I do not recommend a single or one-sided heel lift without first determining from a biomechanical examination whether there is a leg length difference. The addition of a lift to the affected side might change the total biomechanical function.

SHIN SPLINTS

Definition
The term "shin splints" is designed to mean any symptoms characterized by pain and discomfort in the lower leg. The Standard Nomenclature of Athletic Injuries written by the American Medical Association defines shin splints as "pain and discomfort in the leg from repetitive running on hard surfaces or forcible use of foot flexors: diagnosis should be limited to musculocutaneous inflammations, excluding fatigue (stress) fracture or ischemic (compartment syndrome) disorders." Shin splints are thought to be really a combination of three conditions. The first is Tendonitis, an inflammation of the tendon and/or tendon sheath (tenosynovitis). The second is myositis, or an inflammation of the muscle itself. Third is periostitis, or inflammation of the perisoteum, which is the covering of the bone. Shin splints may be anterior (on the front of the leg) or posterior (on the inside back part of the leg).

Anterior Shin Splints
Studies have determined three major causes of anterior shin splints: 1) muscular imbalance, 2) training on hard surfaces and 3) improper foot function or overpronation.

In running, the muscles on the front of the leg function in two ways. They help lift the foot so it clears the ground, then act to allow the foot to reach the ground again without slapping. There is a tendency for an imbalance to occur between the muscles on the front of the leg and those on the back (calf). This imbalance causes the foot to be pulled downward more, and the muscles on the front of the leg have to overwork to lift the foot up.

Running on hard surfaces causes a jarring effect on the muscles. The muscles splint or tense themselves in an attempt to decrease the stress and easily become overused and fatigued.

Excessive proration or improper foot function makes the muscles overwork. If the foot structure is not aligned properly, the muscles and their tendons must try to compensate to stabilize an otherwise unstable structure. The result is muscle fatigue and overuse.

Anterior shin splints are generally seen in athletes who are just beginning to run, or not yet well-conditioned. Their pain usually begins as a tightness in the lower leg.

Treatment
Anterior shin splints is best treated by correcting the cause of the problem. This most frequently is by using an orthotic. Treatment of the symptoms is by using ice massage, appropriate physical therapy, good flexible, shock absorbing shoes, proper training surfaces, and strengthening exercises for the muscles on the front part of the leg.

Posterior Shin Splints
The posterior tibial tendon's primary function is to support the arch of the foot. This muscle originates in the medial or inside aspect of the leg. It courses down just in back of the inner ankle bone and then attaches into the arch of the foot. Overuse of this muscle-tendon complex causes posterior shin splints. There are two main reasons for this overuse. First is overpronation, or an increased amount of pressure on the inner aspect of the foot greater than the muscle-tendon's ability to support the area. This leads to irritation and inflammation. A second cause is a leg length discrepancy. The foot on the long leg side will overpronate or roll in, while the foot on the short leg will attempt to oversupinate or raise the inner aspect of the arch. This causes an over use of the posterior tibial muscle-tendon complex.

We usually see posterior shin splints in an athlete who has been running for an extended period of time. Unlike the anterior shin splint runner, the posterior shin splint symptoms usually take a longer time to manifest themselves because of overuse, and not because of lack of conditioning.

Studies have shown that stress fractures of the tibia can occur frequently seven centimeters above the inner aspect of the ankle bone. Often this fracture is misdiagnosed in the early stages as a shin splint. X-rays or other special studies must be performed to make a proper diagnosis.

Another structure frequently overlooked that causes posterior shin splints is the long toe flexor tendons. They are located anatomically very close to the posterior tibial muscle and tendon. The long flexors work to provide a grasping action of the toes. If this action is decreased or absent, as it often is in overpronation, posterior shin splint like symptoms appear. Besides using orthotics to control the overpronation, a special crest pad must be fabricated in the area where the toes meet the ball of the foot, commonly called the sulcus. This crest pad allows the toes to grasp against resistance and helps strengthen the long toe flexors.

A serious problem associated with the posterior tibial muscle-tendon complex is a partial or complete rupture of its tendon. This usually presents as pain in the arch of only one foot. Besides the obvious deformity of the foot and decrease in arch height, it presents with long-term pain and inflammation. Supportive therapy is usually not satisfactory, and surgery may be indicated.

COMPARTMENT SYNDROMES

Definition
The lower leg is divided into compartments or divisions. These compartments contain muscles that function to move the foot. Except for some blood vessels and nerves, these compartments are essentially closed spaces. Overuse or injury can cause the muscles in these compartments to swell, resulting in excessive pressure and pain. Immediate treatment is required to reduce the pressure because muscular or nerve damage can occur in as little as 18 hours.

Causes
There are three causes of a compartment syndrome: 1) strenuous muscular activity, 2) fractures, sprains, and contusions, and 3) blood vessel injuries and diseases.

Strenuous muscle activity or severe overuse is by far the most common problem associated with running and compartment syndromes. Statistically, there is a history of severe unaccustomed exercise. It usually is seen in males whose aver age age is 23 years old. The right leg is affected twice as often as the left. The microcirculation to the muscle is decreased or cut off entirely, and severe pain results.

Treatment
In mild cases, application of ice to the lower legs and decreased activity reduces the swelling and the pain subsides. In more severe cases treatment should include ice massage, elevation, and bed rest with the leg elevated. Very close observation is mandatory. If the pressure cannot be decreased in the leg, muscle and nerve damage can occur. Surgery may be necessary. It is possible to measure the actual pressure in the compartment affected by inserting a special needle. Normal pressure is about 35 millimeters of mercury. If a reading of 50 to 60 millimeters of mercury is obtained, it is considered abnormal. Fortunately, the most severe type, where the pain will not subside with conservative care, occurs in only one percent of all compartment syndromes seen.

Summary
Some of the most common injuries to runners occur in the lower leg. They include Achilles Tendonitis, shin splints, stress fractures, and compartment syndromes. They are usually caused by overuse, faulty foot structure and leg length discrepancies.

Symptoms are treated with ice massage, physical therapy, anti-inflammatories and rest. The causes are best treated by a careful, complete, biomechanical examination and the use of orthotics.