The tarsometatarsal joint, in the middle of the foot, is a complex structure that connects the forefoot to the midfoot. More formally known as the Lisfranc joint complex, it plays a substantial role in stabilizing the foot’s arch and enabling movement. This network of bones, ligaments, and cartilage absorbs the stress of daily activities, from standing to running. Understanding its purpose is key to appreciating how an issue in this area can affect a person’s mobility.
Anatomy and Function of the Tarsometatarsal Joint
The tarsometatarsal joint is not a single joint but a series of articulations that give the midfoot its combination of stability and flexibility. It is formed where the five metatarsal bones of the forefoot connect with the three cuneiforms and the cuboid tarsal bones. The first metatarsal connects to the medial cuneiform, the second and third metatarsals articulate with the intermediate and lateral cuneiforms, and the fourth and fifth metatarsals connect to the cuboid bone. This arrangement creates a transverse arch across the foot.
This joint’s stability relies on a dense network of ligaments. The most notable is the Lisfranc ligament, a strong band of tissue that connects the medial cuneiform to the base of the second metatarsal. This ligament is important because there is no direct ligamentous connection between the first and second metatarsals. The bony architecture, where the base of the second metatarsal is recessed between the medial and lateral cuneiforms, acts like a keystone in an arch, providing structural integrity.
The primary function of this joint complex is to maintain the arch and provide a rigid lever for the push-off phase of walking and running. While the individual joints allow for only slight gliding movements, their collective action is fundamental for transferring forces from the lower leg to the front of the foot. The medial column is the most rigid, while the lateral column has more mobility, allowing the foot to adapt to uneven surfaces.
Common Injuries and Conditions
Injuries to the tarsometatarsal joint are grouped under the term “Lisfranc injury,” which describes a spectrum of damage from mild sprains to severe dislocations with fractures. A Lisfranc sprain involves the stretching or partial tearing of the ligaments that support the midfoot, particularly the Lisfranc ligament itself, which can cause instability in the joint complex.
More severe trauma can lead to fractures of the metatarsal or tarsal bones and dislocations, where bones are forced from their normal positions. These injuries can be caused by direct force, such as a heavy object falling on the foot, or indirect force, like a sudden rotational twist on a downward-pointed foot. Such injuries are common in sports like football or soccer, or from a simple misstep.
Over time, particularly after a significant injury, the joint can develop arthritis. This condition, known as post-traumatic arthritis, involves the breakdown of the smooth cartilage covering the ends of the bones, leading to pain and stiffness. Osteoarthritis, a degenerative joint disease, can also affect the joint, sometimes developing years after the initial trauma.
Signs and Diagnostic Process
An individual with this injury often experiences significant pain and swelling on the top of the midfoot, which worsens with standing or pushing off the foot. A key indicator of a Lisfranc injury is bruising on the sole of the foot, a sign known as plantar ecchymosis. In severe cases, the person may be unable to bear weight on the affected foot.
When a Lisfranc injury is suspected, a physical examination is performed to assess the damage. A doctor will palpate the midfoot to locate specific points of tenderness. They may also perform stress tests, such as gently twisting the forefoot while holding the heel steady, to check for instability between the bones.
To confirm the diagnosis and determine the severity, imaging studies are required. Weight-bearing X-rays are useful, as they can reveal a widening of the space between the first and second metatarsals, a sign of a Lisfranc ligament tear. A CT scan may be ordered for a more detailed view of the bone structure to detect subtle fractures. An MRI is the most effective imaging tool for assessing soft tissue damage, such as torn ligaments.
Treatment Approaches
The approach to treating a tarsometatarsal joint injury is determined by the joint’s stability and the severity of the damage. For minor, stable injuries like a mild sprain where bones have not shifted, non-surgical treatment is often sufficient. This involves immobilization in a non-weight-bearing cast or boot for several weeks to allow the ligaments to heal.
When the injury is unstable, with displaced bones or completely torn ligaments, surgery is necessary to restore proper alignment. The most common surgical procedure is an open reduction and internal fixation (ORIF). During an ORIF, the surgeon makes an incision to realign the displaced bones, which are then held in place with hardware like screws and plates.
In cases of severe arthritis or injuries with extensive damage where the joint cannot be repaired, a joint fusion, or arthrodesis, may be performed. This procedure removes the damaged cartilage and fuses the bones of the joint together with screws and plates, creating one solid bone. While this eliminates motion at the joint, it also eliminates the pain associated with movement in a severely damaged joint.