A syndesmosis test is a physical evaluation to check the stability of the ligaments that form the ankle syndesmosis. These ligaments connect the two bones of the lower leg—the tibia and the fibula—just above the ankle joint. The assessment involves specific manual maneuvers designed to stress these connective tissues to identify potential damage and determine their integrity.
Understanding the Syndesmosis Injury
A syndesmosis test is used to diagnose a “high ankle sprain.” This injury is distinct from a typical lateral ankle sprain, which affects the ligaments on the outside of the ankle. A high ankle sprain involves the syndesmotic ligaments, which act as shock absorbers, preventing the two leg bones from spreading too far apart when you bear weight. Damage to these structures accounts for a smaller percentage of all ankle sprains but can be more debilitating.
The mechanism for a high ankle sprain involves a significant force, often from a sudden twisting or turning motion while running or jumping. This injury is frequently seen in collision sports like football, soccer, and ice hockey. The cause is a forceful external rotation, or outward twisting, of the foot while it is in a flexed position. This action forces the talus bone to push the fibula away from the tibia, stressing the ligaments that bind them.
Symptoms that warrant a syndesmosis test include pain located above the ankle joint, which can radiate up the leg. This pain worsens with weight-bearing activities or when pivoting on the foot. Unlike more common ankle sprains, a high ankle sprain may not present with significant swelling or bruising, which can lead individuals to underestimate the severity of their injury.
Common Physical Examination Tests
Clinicians use several specific maneuvers to assess the syndesmosis. One of the most common is the “Squeeze Test,” also known as the fibular compression test. During this test, a provider squeezes the tibia and fibula together at a point midway up the calf. If this compression produces pain lower down in the leg, near the ankle syndesmosis, it indicates a high ankle sprain. The pain should be felt distally, not at the point where the pressure is applied.
Another common evaluation is the “External Rotation Test.” For this test, the patient sits with their knee bent at a 90-degree angle and the ankle in a neutral position. The clinician stabilizes the lower leg with one hand while using the other to gently grasp the foot and rotate it outwards. Pain felt over the syndesmosis during this motion suggests an injury to the ligaments.
These physical tests are designed to reproduce the mechanism of injury on a smaller scale to stress the syndesmotic ligaments and pinpoint the source of pain. A positive result in one or more of these tests raises the clinical suspicion of a high ankle sprain, guiding the next steps in the diagnostic process.
Interpreting Test Results and Next Steps
A positive result from a syndesmosis test, where the maneuver reproduces the patient’s pain, strongly indicates a high ankle sprain. Conversely, a negative test makes a syndesmosis injury less likely. However, these physical examinations provide strong clues but are not definitive on their own and are part of a larger diagnostic puzzle.
Following the physical examination, the next step is diagnostic imaging to confirm the suspected injury. Weight-bearing X-rays are often ordered first to check for any abnormal widening between the tibia and fibula. This widening would indicate that the ligaments are no longer holding the bones together properly.
If the X-rays are inconclusive or if a more detailed view is needed, a magnetic resonance imaging (MRI) scan may be ordered. An MRI is effective at visualizing soft tissues, allowing the provider to see the ligaments directly and assess the extent of any damage. This imaging confirms the diagnosis and helps determine the sprain’s severity for creating an appropriate treatment plan.