The feet are the workhorses of the body. They support the weight of the entire body, maintain balance, and propel the body when walking. A posterior night splint is commonly used in instances when tenderness or discomfort in the foot prevents restful sleep and the resting position of the foot at rest causes a spike in pain upon waking or with the first attempts use the foot upon rising.
During sleep the ankle relaxes and tends to point the foot downward, a position known as "plantar flexion." This can cause extra pressure on the heel and added stress throughout the foot, especially in the arch area. Using a posterior night splint, also referred to as a resting splint can alleviate heel pressure and maintain the foot in a neutral position, around ninety degrees of ankle flexion, the position adopted during standing.
Across the bottom of the foot, running from the heel to the toes, is a thick strip of tissue called the plantar fascia. When this area becomes irritated and inflamed, it can cause pain in the foot, especially in the arch and the heel. Resting with the toes pointed away from the body only aids in increasing the tightness of this band. Supporting the foot during sleeping with a posterior resting splint stretches both the plantar fascia and the calf, including the Achilles tendon, the thick fibrous band on the posterior or back of the ankle that connects to the heel, to minimize morning stiffness and pain.
A posterior night splint comes in several styles. Some are soft and wrap around the foot and ankle — excluding the heel — and come with a strap to pull the toes upwards. Others are created from Velcro® straps that wraps around the lower calf and the arch of the foot with a plastic upright stays to maintain proper foot positioning. These types of posterior night splints are a good option when plantar fasciitis, or the inflammation of the fascia in the arch of the foot, is the problem.
A boot-like posterior night splint, on the other hand, are more suitable for foot pain due to issues such as heel spurs, a condition where the heel bone develops an abnormal hooked outcropping, or heel pressure when sleeping, in addition to plantar fasciitis. This type of posterior night splint also comes with some form of upright pulley system to keep the foot in a good position. Another benefit to a boot is that the foot can be positioned in such a way that the heel does not come in contact with the splint or the bed. This is advantageous for people who are prone to bed sores.