The metatarsophalangeal joint (MTP joint) is the joint between the metatarsal bones, the bones that makes up the foot, and the proximal phalanges, the bones of the toes. This joint is the joint that moves when you bend your toes. It is classified as a condyloid joint, because it is rounded at the end of one the phalanges and it is very close to the shallow cavity of the metatarsals.
There are several ways the metatarsophalangeal joint can move, including abduction, adduction, flexion, and extension. The two most common movements are flexion and extension. Flexion is bending, or curling, the toes downward, and extension is bending the toes upward. Abduction and adduction are less common movements and can typically only be done by grabbing the toes and moving them with your hands. Abduction moves the toe away from the midline of the body, and adduction moves toes toward the midline of the body.
The metatarsophalangeal joint can be the site of several types of injury and disease. Arthritis or gout can affect the joint and cause it to be stiff and painful. A bunion, an enlargement of the tissue or bone at the base of the big toe, can also form near the bone and cause painful movement. Bunions are caused by constant irritation of the area around the joint, usually as the result of ill-fitting footwear.
Sprains are the most common injuries to the metatarsophalangeal joint. More commonly known as turf toe or tennis toe, it is usually caused by repetitive stopping and starting when running, which stretches and strains the ligaments. Due to the inflammation of the tendons on the top and bottom of the big toe, it causes the joint to swell and turn red. It is not unique to just tennis players, and often occurs in people who play soccer, football, basketball, and rugby.
It can be a challenge to repair an injury of the metatarsophalangeal joint, due to the anatomy of the toe and foot. The way the joint articulates when moving makes it difficult to tape or brace it to stop it from moving, which is mandatory for proper healing. Ideally, all activity has to be stopped to allow it to heal. This can be difficult, especially for athletes.
In addition to taping or bracing a sprain of the metatarsophalangeal joint, wearing a shoe with a stiff sole and cushioned inner sole can prevent movement. A sprain will take about a month to heal, if properly taken care of. If left untreated, the situation can become chronic as it never heals properly, and can lead to malformation of the joint.