Jumping and landing are important skills in sports like basketball, soccer, and volleyball. Ankle sprains make landing difficult. Pain, swelling, and giving way of the ankle lead to functional ankle instability (FAI). FAI occurs when the ankle is unstable but the ligaments aren't damaged.

Sports researchers are looking for a way to explain what causes FAI. In this study scientists try to find a way to measure hidden joint deficits that lead to instability. They compare two groups using two tests. One group included healthy adults with normal ankles. The second group had FAI. The first test was stepping down from a five-inch height. The second test was a forward standing jump.

There were no differences in the groups in terms of ankle stiffness or laxity. Group differences were seen with the jump test. The jump test was harder because strength, coordination, and ankle stability are needed. Any ankle swelling may decrease the joint's ability to sense motion and position.

The authors conclude that the jump test is a better way to find hidden ankle problems than the step-down test. They recommend its use for anyone with FAI. Finding and correcting such problems with stability may help prevent future re-injuries.