Plantar fasciitis is the tearing, inflammation and subsequent degeneration of the plantar fascia, a broad ligament-type structure which extends across the bottom of the foot. The plantar fascia supports the arch and increases the rigidity of the foot, aiding the calf muscles in propelling the body forward during walking. Excess stress on the plantar fascia can cause microscopic tears within the fascia resulting in pain, typically at the inside of the heel.
Ligaments and similar structures will contract and tighten when injured. At rest and during sleep, the foot is relaxed, which allows the plantar fascia to contract. An injured fascia will tighten, shorten and contract during periods of rest, especially long periods of rest during the night. Upon waking and stepping down, the shortened plantar fascia is placed under a considerable load. The fascia acts like a cable and pulls on the heel bone, causing a sharp, immediate pain. Small microscopic tears may occur in the fascia near the heel bone. As weight is gradually applied to the foot, the fascia slowly elongates and the pain eventually disappears.
The goal of a soft night splint is to keep tension on the plantar fascia during the night to prevent shortening and assist in healing. The diagram above illustrates the plantar fascia and foot in a relaxed position, the eventual shortening and tightening of the plantar fascia at rest, the tearing of the fascia when standing and how night splints help to keep the fascia stretched out during sleep.
Some night splints are rigid and others are soft. Patients tend to tolerate the soft night splints better than the rigid night splints, yet many doctors prefer the rigid night splints for their patients. The Strassburg Sock is one of the most popular night splints for treating plantar fasciitis. The Strassburg Sock fits over the leg, like a sock, and extends to just below the knee. A velcro strap wraps around the top of the leg to hold it in place and another strap extends from the toes to the front of the leg. The strap pulls up the toes and the ankle, stretching both the plantar fascia and the calf. The popularity of the Strassburg Sock is due to it’s comfort, ease of use and affordability.
An article published in the Journal of Foot and Ankle Surgery in 2002 found the Strassburg Sock effective at treating plantar fasciitis. In the study, 89 patients were instructed to use the Strassburg Sock for at least 6 hours per night. All 89 patients were able to wear the sock as prescribed. Ninety-eight percent of patients recovered after 8 weeks of treatment. Although rare, some complaints with use of the Strassburg Sock include too much leg compression, ankle discomfort and the development of ingrown toenails. Due to these problems, the Strassburg Sock should not be used in individuals with circulatory problems, extra large calves, ankle arthritis or a history of ingrown toenails, unless recommended by a physician.
The Thermoskin Plantar FXT is another soft night splint designed to treat plantar fasciitis. The FXT is shorter and wraps around the ankle, but still pulls up on the toes, stretching the plantar fascia. The Thermoskin products are designed for heat retention and clinically proven to elevate surface temperatures 1 degree Celsius. The benefits of heat retention include increased blood flow to soft tissue to facilitate healing. It has been shown that increased temperatures speed healing of chronic musculoskeletal injuries, but there is no research on the use of Thermoskin FXT in plantar fasciitis. The Thermoskin FXT tends to be the more comfortable night splint for those who have large calves and small ankles and for those who have difficulty wearing tight socks. The Thermoskin FXT does stretch the plantar fascia, but does not stretch the calf muscle.
Many physicians recommend rigid night splints for their patients because the rigid splints hold the foot and ankle in a better position, stretching the calf and plantar fascia during the night. Although studies have found rigid night splints effective, many patients cannot wear them through the night because they find them bulky and uncomfortable. Another issue with rigid night splints is the natural tendency to press the forefoot down on the base of the splint, lifting the heel slightly out of the splint. Many patients awake with their foot in a plantar flexed (relaxed) position, which does not keep the calf or plantar fascia stretched, nor does it facilitate healing. Rigid night splints can be very effective in the treatment of plantar fasciitis when they are fit properly and worn throughout the night.
Dorsal night splints fit on the front of the ankle and leg. They are also designed to keep the ankle dorsiflexed during the night. They do not have a separate portion to pull up the toes and stretch the plantar fascia, but many patients find them less bulky and more comfortable than the traditional rigid night splint. Those with large calves or large ankles generally have difficulty with fit.
For more diagnosis and treatment information, visit our plantar fasciitis information page.