Plantar fasciitis is characterized by sharp heel pain occurring at the first step in the morning or upon rising after periods of rest. Fasciitis is caused by microscopic tears in the plantar fascia, a long connective tissue structure in the bottom of the foot. The tearing of the fascial band results in inflammation and eventual deterioration. The plantar fascia is composed of mostly collagen, but also elastin and long carbohydrates chains called glycosaminoglycans, or GAGs. The organized network of collagen adds to it’s strength, the elastin allows for stretching and the GAGs attract water, improving resiliency.
Musculoskeletal disorders often occur in association with thyroid disease, particularly with hypothyroidism. Common musculoskeletal complaints in patients with hypothryoidism are muscle tenderness, generalized joint pain, cramping and weakness. Specific musculoskeletal disorders, such as adhesive capsulitis and carpal tunnel syndrome, have been linked to hypothyroidism. It is theorized that hypothyroidism may cause plantar fasciitis for the same reason other musculoskeletal conditions occur in hypothyroid patients. The disorders result from low thyroid levels causing deposits within the connective tissue. Thyroid hormone inhibits fibroblast production and secretion of collagen, elastin and GAGs, all substances important in connective tissue structure. Low levels of thyroid hormone result in the overproduction of these substances, particularly GAGs, which attract water.
Increased deposits of GAGs and the additional water increase the space between the collagen fibers. This disrupts the collagen network and compromises the integrity of the plantar fascia structure. The weakening of the plantar fascia increases it’s susceptibility to microscopic tears. Microscopic tearing occurs when the plantar fascia is placed under excess stress. This commonly occurs with biomechanical conditions, but in a weakened plantar fascia, may occur under normal conditions. The tearing results in inflammation and pain. Due to the early disorganization of the collagen network, progression from plantar fasciitis, an inflammatory condition as a result of tearing, to plantar fasciosis, a degenerative condition, may occur more quickly. Plantar fasciosis is a more difficult condition to treat, which makes early diagnosis and treatment crucial.
Eliminating the stress on the plantar fascia is an important early treatment. This can be accomplished by wearing supportive shoes and inserts and avoiding barefoot walking. Heel lifts, or shoes with a small heel, will also take stress of the arch. Heel cups may help alleviate symptoms, but will no decrease the stress on the plantar fascia or improve the condition. Weight loss will decrease stress on the arch, unfortunately weight gain is common in patients with hypothyroidism and weight loss tends to be difficult. Stretching both the calf and the arch are important in the healing process and specific stretching regimens should be initiated immediately after diagnosis. A night splint can facilitate healing and eliminate morning heel pain by stretching the plantar fascia throughout the night.