Clients describe CAI as a feeling of “giving way” and instability resulting in swelling, prolonged pain, increased or (if ankle sprain has previously occurred) limited range of motion. CAI often leads to ankle injuries and, most commonly, ankle sprains. The three most common ankle sprains are: inversion sprains (the sole of the foot is rotated inward to face the other foot), eversion sprains (the rotation is outward and usually affects deltoid ligaments), and high ankle sprains (harm to the syndesmotic ligaments). 75% of all ankle injuries are sprains and 85% of all ankle sprains are inversion sprains, which tend to recur. People most affected by CAI are usually physically active. Those that tend to have lax ankle ligaments (mechanical issue) and have an active lifestyle (functional issue) tend to suffer from CAI the most. Those with a cavus foot (high arch of the sole of the foot) are also more likely to have CAI, particularly, lateral ankle instability. If the joint is stable, intact and ligaments are strong, injury is less likely to occur.
Anterior talofibular ligament is the most commonly injured and also the weakest ankle ligament. ATFL inversion sprain can occur when a foot is inverted and plantarflexed (the position of the foot when toes are pointed out) while the leg is externally rotated (leg is turned to point to the side). The next most common sprain is a tear in the calcaneofibular ligament (CFL) often followed by a tear of the AFTL. A sprain of the posterior talofibular ligament (PTFL) of the outer side of the ankle is least common of the three because it’s the third weakest ligament. The medial (inner or facing the midline) ligaments are: tibiocalaneal, tibionavicular, superficial tibiotalar, and posterior tibiotalar ligaments and are least likely to be sprained.
As part of the assessment, the physician would often order stress radiographs and X-rays. To estimate loss or return of functional ankle control and predict future ankle injury postural control is used. Postural control is one’s ability to keep centre of mass centred over one single foot. Most commonly, to improve postural control taping, bracing, and orthotics are used. In extreme cases, the physician may recommend reconstructive surgery of the ankle.