This study aims to comprehensively explore the relationship between changes in muscle architecture and connective tissue structure in athletes with ankle sprains and the intrinsic biomechanical risk factors observed in these individuals. The main goal of the research is to compare the risk factors associated with ankle sprains, characteristics of lower extremity muscle architecture, and structural features of the anterior talofibular ligament (ATFL) between athletes with and without a history of ankle sprains. Additionally, the study seeks to identify intrinsic factors that may lead to lateral ankle sprains and to investigate the link between these factors and structural changes related to chronic ankle instability. Overall, the study aims to contribute scientifically to the early detection of sprain risk in athletes and the development of personalised preventative intervention strategies.

The hypotheses of the study are as follows:

Hypothesis 1: In athletes with a history of ankle sprains, the strength of the muscles surrounding the ankle differs from that of their uninjured ankles and ankles of the athletes without a history of sprains.

Hypothesis 2: Athletes with a history of ankle sprains have a different level of proprioception (position sense) compared to athletes without a history of sprains.

Hypothesis 3: Athletes with a history of ankle sprains have different muscle and ligament sizes compared to their uninjured legs and the legs of athletes without a history of sprains.

Hypothesis 4: Dynamic balance differs between athletes with a history of ankle sprains and those without a history of ankle sprains.

Ankle instability exhibits a significant propensity to evolve into a chronic condition. Chronic ankle instability (CAI), defined by enduring residual symptoms following a sprain, recurrent sprains, and perceived instability, occurs in approximately 10% to 40% of cases. According to research conducted by Van Rijn and colleagues, between 5% and 33% of patients continued to experience pain one year subsequent to an ankle sprain, and one-third of the participants reported at least one re-sprain three years thereafter (4, 6).

Research indicates that a minimum of 73% of individuals who have sustained an ankle sprain exhibit persistent symptoms, including pain, a sensation of instability, proprioceptive disturbances, and impairments in neuromuscular control (7, 8). This condition presents a significant risk of both re-injury and the development of CAI. A history of multiple sprains and recurrent feelings of instability are identified as CAI, and the ongoing nature of this condition increases joint damage and the likelihood of osteoarthritis (9). The treatment and prevention of these injuries are costly and hinder athletes' return to training and competition (10).

Numerous intrinsic risk factors have been identified in the literature concerning the incidence and recurrence of lateral ankle sprains. These risk factors include a previous sprain history, gender, height, body weight, anatomical foot posture, alignment abnormalities (e.g., pes cavus, genu varum), joint laxity, joint range of motion, muscle strength, proprioception, reaction time, and postural control (11). Current studies show that, although there are differences in performance levels between genders, there is no significant difference in exposure to injury risk (12, 13). Conversely, it is stated that a direct relationship exists between height, body weight, ankle laxity, muscle strength, and postural control and lateral sprains (7). When assessed in terms of muscle strength, weakness in the ankle and hip muscles is an important risk factor for the development of LAS. Research shows that athletes with more than 15% strength asymmetry, especially during the pre-season, face a higher risk of sprain compared to those without such asymmetry. Postural balance disorders are also regarded as a significant intrinsic risk factor in the development of LAS. In conclusion, ankle sprains are common injuries among athletes and can lead to significant functional impairments. Identifying intrinsic risk factors for these injuries and implementing targeted preventive strategies through individual assessments are essential for both injury prevention and reducing the development of OAS. A review of current literature shows that there are limited studies that thoroughly examine changes in the architecture and functional performance of the muscles around the ankle in athletes who have experienced recurrent ankle sprains. This study aims to comprehensively explore the relationship between changes in muscle architecture and connective tissue structure in athletes with ankle sprains and the intrinsic biomechanical risk factors observed in these individuals.

Inclusion Criteria:

1. At least 5 years of active participation in any sport.
2. Age between 18 and 35.
3. A history of at least two clinically diagnosed LAS episodes with inflammatory symptoms like pain and swelling.
4. The last sprain occurred at least 3 months before the study start, and the participant has fully returned to their sport.
5. No previous surgeries affecting

Exclusion Criteria:

1. Any history of ankle fracture.
2. Surgery or systemic disease impacting sensorimotor function in the lower limb.
3. Neurological disorders.
4. Recent (within a month) acute injury to the lower extremity.
5. Visual or vestibular issues that impair balance or coordination.

This study is a retrospective, cross-sectional investigation conducted to evaluate the relationship between intrinsic risk factors, including muscle and ligament sizes, dynamic balance, postural stability, proprioception and ankle instability in athletes diagnosed with chronic ankle instability (CAI). Participants will be equally recruited into the group with athletes who have a lateral ankle sprain history (LAS Group) and the Control group, with consideration for gender stratification (groups will have the same number of males and females).