The purpose of the study is to identify if there is a relationship between the frontal plane projection angle as a measure of dynamic knee valgus with foot posture, pain, and dynamic balance in chronic ankle instability patients.

The study design is an observational, correlational study to find if there is any relationship between the frontal plane projection angle with foot posture, pain, and dynamic balance in chronic ankle instability non-athletic patients.

The sample size is estimated to be 84. The frontal plane projection angle will be measured using a single-leg squat test and analyzed using Kinovea software.

Foot posture will be measured using the foot posture index. pain will be measured using a numerical rating scale. dynamic balance will be measured using modified star excursion balance tets

Inclusion Criteria:

• A history of at least 1 significant ankle sprain.
• The initial sprain must have occurred at least 12 months prior to study enrollment.
• The most recent injury must have occurred more than 3 months prior.
• Additionally, a sprain that was associated with inflammatory symptoms (pain, swelling, etc.), Created at least 1 interrupted day of desired physical activity.
• A history of the previously injured ankle joint as "giving way" and/or recurrent sprain and/or "feelings of instability." And the self-reported outcome measure foot and ankle ability measure (FAAM): ADL scale <90%.

Exclusion Criteria:

• History of previous surgeries or fractures to the musculoskeletal structures (i.e., bones, joint structures, nerves) in either limb.
• No acute injury to musculoskeletal structures of other joints of the lower extremity in the previous 3 months, which impacted joint integrity and function (i.e., sprains, fractures) resulting in at least 1 interrupted day of desired physical activity.
• Participants were screened to exclude scoliosis using the Adam's Forward Bend Test (AFBT).

The sample will be recruited from the outpatient clinic of the Faculty of Physical Therapy at Cairo University by referral from the orthopedic doctor diagnosed with chronic ankle instability.