Lateral ankle sprains are one of the most common athletic injuries. Even more concerning is the high recurrence rate after an initial sprain. The development of repetitive ankle sprains and persistent symptoms after injury has been termed chronic ankle instability (CAI). One of the purported causes of CAI is mechanical ankle instability (MAI).MAI results in abnormal ankle mechanics. Both hypermobility and hypomobility may change a joint's axis of rotation and result in abnormal joint mechanics. The role of hypermobility, or laxity, has been examined extensively in the literature, but more recently the role of hypomobility has also been examined. There may be a relationship between the two, with implications at the talocrural, subtalar, and inferior tibiofibular joints.Assessment and treatment should focus on both hypermobility and hypomobility and although injury may seem to be isolated to the talocrural joint, the inferior tibiofibular and subtalar joints should also be thoroughly examined.