70% of the general population suffers ankle injuries at least once in their lifetime. The ankle lateral ligament injuries cause an average of 6.9 days of work loss, and it has been reported that the quality of life of these patients is affected by their long-term results. Exercise training is important to prevent job loss, increase individuals' quality of life, or speed up their return to work. Functional or chronic insufficiency resulting from ankle ligament injury results in various abnormalities in the lower extremity. Motor coordination disorders due to instability, adhesions, peroneal muscle weakness, and loss of proprioception can be seen in the talus or subtalar joint. Instabilities are usually caused by loss of strength after an acute lateral ligament injury, hypomobility in the joint, inadequate improvement in proprioception, or inadequate healing of the ligament.

Almost 40% of patients with lateral ankle injury develop a condition known as chronic ankle instability. The cause of chronic ankle instability is classified as mechanical ankle instability (MAI) and functional ankle instability (FAI). While MAI is caused by ligament laxity, other factors such as proprioceptive problems, neuromuscular problems, postural control deficiencies, and muscle weakness are caused by FAI. For this reason, peroneal muscle strengthening, Achilles tendon stretching, balance training, and proprioceptive training are shown as the most important components of the treatment program in the rehabilitation of ankle instabilities. (5) It has been reported by many researchers that functional instability can be reduced and repetitive injuries can be prevented in patients given proprioceptive training and peroneal muscle strengthening on the balance board. In the results of another study evaluating bilaterally in the lower limb after balance training given to the intact side in individuals with chronic ankle instability, it was stated that the balance function of the unstable ankle was developed.

Although the treatment methods of ankle instability vary, there are very limited studies comparing treatment methods unilaterally and bilaterally in the ankle lateral instability in the literature. Our study will contribute to the literature to the next rehabilitation programs by comparing unilateral and bilateral exercise training prepared by rehabilitation protocols in many ways in two different groups.

Ankle ligament injuries are one of the most common musculoskeletal injuries among physically active people, accounting for ~ 14% of all sports-related orthopedic clinic visits. And it is stated that injuries that delay the return to sports the most. 4% of these injuries and the most common are the lateral ankle ligament injuries. 70% of the general population, not only specific to sports, suffers ankle injuries at least once in their lifetime. The ankle lateral ligament injuries cause an average of 6.9 days of work loss, and it has been reported that the quality of life of these patients is affected by their long-term results. When people who play sports are taken into consideration, an ankle sprain can affect the quality of life of the individual, as well as reduce performance and keep it away from education and competition.

Ankle sprains often occur during physical activities such as basketball and football, which require sudden stops, bounces, landings, and swings around a stable foot. Most lateral ankle sprains occur when combined with excessive inversion or adduction with additional plantar flexion.

Functional or chronic deficiencies develop in the lower limbs as a result of ankle ligament injury, resulting in various abnormalities. Motor coordination disorders due to instability, adhesions, peroneal muscle weakness, and loss of proprioception can be seen in the talus or subtalar joint. Instabilities are usually caused by loss of strength after an acute lateral ligament injury, hypomobility in the joint, inadequate improvement in proprioception, or inadequate healing of the ligament. Almost 40% of patients with lateral ankle injury develop a condition known as chronic ankle instability (CAI). CAI is characterized by the occurrence of recurrent cases of instability that cause constant ankle sprain and the giving-way sensation of the ankle after the first ankle sprain. The diagnostic criteria are detailed in the International Ankle Consortium, Cumberland Ankle Instability Tool (CAIT) is often used to evaluate functional ankle instability.

Among the most important factors causing instability in the ankle are proprioceptive disorders, pain, and muscle weakness. Therefore, rehabilitation programs generally focus on exercises that include muscle strengthening, balance training, neuromuscular training, and proprioceptive training protocols. In another combined supporting study, Huang et al. investigated the effects of combined balance exercises with plyometric exercise against plyometric exercise in individuals with functional ankle instability and showed that the combined program will reduce postural oscillation in static conditions, and improve stability and energy propagation models in dynamic postural control. One of the factors contributing to CAI is thought to be the loss of strength of the ankle circumference muscle groups in both concentric and eccentric directions. It is assumed that a decrease in the strength of the muscles of the more proximal joints, such as knee and hip, not just ankle oriented, may also be effective in the formation of CAI.

It has been shown in systematic review and meta-analysis that proprioception disorder contributes to chronic ankle imbalance. In another study in individuals with unilateral chronic ankle instability, both extremities were evaluated in terms of strength and proprioception, a decrease in the sensation of kinesthesia was observed, and loss of eversion force and proprioceptive disorders were reported on both sides.

Although ankle instability treatment approaches vary widely in all these studies, there is no detailed study comparing applications unilaterally and bilaterally in the literature. Our study will contribute to the literature to the next rehabilitation programs by comparing unilateral and bilateral exercise training prepared by rehabilitation protocols in many ways in two different groups

Inclusion Criteria:

• Being a volunteer between the ages of 18-45
• Mild (grade I), Moderate (grade II) or severe (grade III) lateral ankle sprain
• Ability to understand and apply Turkish written and verbal instructions.

Exclusion Criteria:

• Being an athlete
• Previous surgical interventions for the musculoskeletal system structure on both lower extremities
• History of fractures in both lower extremities
• Acute injury of musculoskeletal structures of other lower limb joints in the past 3 months
• Presence of chronic pain and edema in the foot or ankle unrelated to sprains
• Presence of other lower extremity injuries
• To have received a physiotherapy and rehabilitation program in the last 3 months