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The mysterious sinus tarsi syndrome

Life is full of hazards, be they emotional or be they physical. Depending on the location, a variety of complications can result from an injury, even one that is seemingly mild. Tweak a knee joint, or twist an ankle, and damage can occur to one of the vital structures composing these complex articulations. Being careful is wise but accidents still happen.

Ankle sprains are one of the most common joints injured, occurring to the athlete and average citizen alike. Although estimates vary greatly, almost two thirds of sprains will have continued problems after the normal course of healing. By definition, a sprain of a joint involves motion farther than the soft tissue and bone structures normally allow for. Movement will stress the ligaments responsible for stabilizing it, stretching them, potentially even tearing them.

Unfortunately, a rather mysterious chronic pain is experienced after many ankle sprains, long after the appropriate course of treatment has been followed. Typically, medical care consists of stabilizing the part with a boot or a soft cast, followed by some rehabbing of the joint (often via physical therapy, but not necessarily). Too often, after many foot or ankle injuries, a vague pain is noted from the region, even when the severity of the initial trauma is seemingly mild.

The sufferer of this malady usually describes a vague, achy pain originating from the ankle region, primarily the area in front of the outer ankle bone (the fibula). People will often mention a feeling of instability, sometimes stating the limb just “gives way” and won’t support them. Being on uneven surfaces, like trail hiking or gardening, typically aggravates the discomfort.

Healthcare providers are generally baffled by this ill-defined pain, which clearly developed following the foot or ankle injury, but is somehow separate, dissociated from the now-pain free ligaments stressed in the primary trauma. For those so afflicted, simply using poorly supportive shoes can increase symptoms. But stepping on a small crack in the sidewalk can lead to sudden intense pain, especially if the foot twists slightly.

This common condition, termed sinus tarsi syndrome, defines a problem with the subtalar joint, which is the joint immediately below the ankle joint. A component of the subtalar joint, along with three articular surfaces, is a space, aka a sinus. But the S-T joint is poorly innervated, resulting in only vague pain sensations when it is inflamed. Hence the ill-defined discomfort originating from this vital structure.

Various kinds of trauma can result in sudden manipulation of the subtalar joint. But also capable of producing recurrent symptoms is a foot type which stresses the joint, seen in both the higher arched foot, as well as those with a lower arch. In any individual with abnormal foot mechanics, pain can develop from this joint over time. This may not be a product of a single traumatic event but, instead, the repetitive injury of each and every step when foot and leg mechanics deviate from the norm.

Sinus tarsi syndrome is associated with some complications: it is a frequent cause of instability and falls. When the mind knows it’s going to experience pain with weight bearing, it may opt to avoid it by not tightening the muscles needed to stand. These individuals describe a sensation of the leg simply “giving way,” allowing gravity to do its thing, and a fall results. Understandably, this particular complication of STS can be devastating in seniors.

Identifying the causative agent is essential in finding an approach that works. Numerous options for care exist, the key is finding the specific reason someone is suffering from this occult problem. Sometimes it is their bone structure, the individual’s foot and leg architecture, a complex topic varying greatly person to person.

Although we have no detailed or precise data concerning its incidence, experts believe this is an everyday occurrence for a multitude of Americans. Typically, because few healthcare providers are familiar with this body part, sinus tarsi syndrome generally goes untreated. Some people will purchase more stable shoes and find some level of relief. Or pain is lessened by adding an arch supportive device inside their shoes.

On occasion, a tightened Achilles tendon will be the primary factor stressing the S-T joint. A directed stretching program, although a time consuming process, can be prescribed by most any healthcare provider. But it is the identification of the structure which is symptomatic that is so essential.

Altering foot and leg biomechanics with some type of supportive device is the solution for many sufferers. (As therapies go, this is one of the easiest. No poking with a needle or getting cut by a knife. Put on your shoes!) An accurately prescribed and fit custom foot orthotic is always going to be the most effective but not everyone needs this level of precision to find relief. Still, it is usually preferable to have too much precision than just enough. (Can something be too comfortable?)

Naturally, an inflamed joint can nearly always be injected with a corticosteroid, aka cortisone. This can be a very effective method of immediate pain relief but often the improvements are temporary. A regenerative medicine technique like prolotherapy is particularly beneficial in this instance and entails minimal risk of complications. Best of all, the benefits are lasting since it is stimulating healing.

There are an abundance of reasons people experience pain from the ankle area. But a vague, aching pain here, aggravated by any twisting motion, may be sinus tarsi syndrome. A specialist well-acquainted with this ubiquitous condition will be better able to assess the situation and how to alleviate the symptoms. As a wise man once said, “foot pain is not normal.” Don’t let anyone tell you it is.

Dr. Conway McLean, DABFAS, FAPWHc, has offices in L’Anse and Marquette. He is a physician who specializes in treating lower leg, ankle and foot problems.

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