This study aims to examine the relationship between lower extremity muscle strength and balance and to compare these parameters between healthy individuals and individuals with lower extremity injuries.

Inclusion Criteria:

Anterior Cruciate Ligament (ACL) Injury Group:

• Aged between 18 and 40 years
• Diagnosed with a unilateral ACL injury 6 to 18 months prior to participation
• Diagnosis confirmed by magnetic resonance imaging (MRI)
• Ability to speak, read, and understand Turkish
• Willingness to participate voluntarily in the study

Chronic Ankle Instability (CAI) Group:

• Aged between 18 and 40 years
• Diagnosed with chronic ankle instability due to recurrent ankle sprains 6 to 18 months prior to participation
• History of at least two ankle sprains
• Ongoing symptoms of functional ankle instability (e.g., episodes of giving way, feelings of instability)
• Ability to speak, read, and understand Turkish
• Willingness to participate voluntarily in the study

Healthy Control Group:

• Aged between 18 and 40 years
• No history of lower extremity injury or orthopedic diagnosis
• Ability to speak, read, and understand Turkish
• Willingness to participate voluntarily in the study

Exclusion Criteria:

• Presence of neurological, vestibular, or visual disorders that may affect balance
• History of other orthopedic diseases or trauma
• Presence of musculoskeletal disorders or cardiovascular comorbidities
• History of physiotherapy, rehabilitation, or surgical intervention within the past 6 months

The study population will consist of adults aged 18-40 years, including individuals with a unilateral anterior cruciate ligament injury, individuals with chronic ankle instability, and healthy controls. Participants with lower extremity injuries will have a confirmed diagnosis within the past 6 to 18 months. All participants will be able to speak, read, and understand Turkish and will voluntarily consent to participate in the study.