A Lisfranc injury involves damage to the bones or ligaments in the midfoot, specifically where the long metatarsal bones meet the smaller tarsal bones. This injury is a spectrum, ranging from a subtle ligament strain to a severe fracture-dislocation that disrupts the entire midfoot structure. While less severe cases may sometimes be mistaken for a simple sprain, damage to this complex joint system can lead to serious instability and requires prompt medical attention.
The Structure of the Lisfranc Joint
The Lisfranc joint complex connects the forefoot to the midfoot, consisting of the five metatarsal bones and the cluster of tarsal bones, including the three cuneiforms and the cuboid. This bony arrangement essentially forms a keystone, providing stability to the arch of the foot. The midfoot is designed to transfer the forces generated by the calf muscles forward, making its integrity fundamental to normal gait.
The stability of this complex is heavily reliant on a network of strong ligaments, most notably the Lisfranc ligament. This short, thick band of tissue connects the medial cuneiform bone to the base of the second metatarsal bone. Unlike the other metatarsal bases, the first and second are not directly connected by an intermetatarsal ligament. This makes the Lisfranc ligament the sole connective tissue providing transverse stability between the first and second rays. Any disruption to this specific point can cause the midfoot to collapse.
Causes Related to High-Energy Trauma
Lisfranc injuries resulting from high-energy trauma involve forces that cause immediate and severe damage to the midfoot. These injuries often result in multiple fractures, severe joint displacement, and extensive tearing of the Lisfranc ligament. The most common scenarios for high-energy Lisfranc disruptions include motor vehicle accidents, which account for a large percentage of these severe cases.
In a car crash, the injury typically occurs when the foot is planted firmly on the brake pedal or floorboard. The immense force travels up the leg and is concentrated on the fixed midfoot, leading to a crush injury or a sudden, forceful fracture-dislocation. Falls from significant heights also drive the metatarsals through the tarsal bones upon landing. High-energy injuries frequently present with obvious deformity and can be complicated by open fractures, almost always requiring immediate surgical intervention.
Causes Related to Low-Energy and Rotational Forces
In contrast to high-energy trauma, many Lisfranc injuries occur from indirect, low-energy mechanisms, which are often subtle. These injuries are particularly common in sports and involve a specific combination of axial loading and rotational force. The characteristic mechanism involves the foot being in a plantar-flexed position, meaning the toes are pointed downward, when the force is applied.
When the foot is plantar-flexed, the ligaments on the top (dorsal) surface of the foot are weakened, making the joints vulnerable to twisting. If the forefoot is fixed, such as when a cleat is caught in the turf or a dancer’s foot is trapped, and the body rotates or falls forward over the foot, the entire force of the body is leveraged against the Lisfranc ligament. This rotational stress tears the Lisfranc ligament, causing the metatarsals to displace from the tarsal bones.
Low-energy injuries can also happen in everyday situations, such as stepping into a small hole, missing a step on a staircase, or twisting the foot awkwardly while stepping off a curb. The initial trauma can lead to the injury being misdiagnosed as a routine sprain, since the damage is often primarily ligamentous. These subtle ligament tears can still result in instability that progresses to chronic pain and arch collapse if not properly identified and treated.