In athletes the repetitive sprain of foot and ankle could lead to acute or chronic hindfoot and midfoot instability. Mechanical instability is defined as laxity and excessive joint motion of the joints caused by structural damage of the supporting ligamentous tissues, which could need operative treatment. Functional instability does not exhibit any physical laxity of the joints because it may be caused by specific insufficiencies in proprioception, neuromuscular control, postural control, or muscle strength, which were mainly treated by physiotherapeutic rehabilitation if there were any neuromuscular disorders previously. Early diagnosis and appropriate treatment are considered vital by the athlete to return to the best sport level as soon as possible.