Introduction: Total knee arthroplasty (TKA) is a widely used surgical treatment method worldwide for advanced pain and functional loss resulting from osteoarthritis and other degenerative knee pathologies. The aim of TKA is to reduce pain, restore joint function, and improve quality of life. Although many patients experience a significant reduction in pain after surgery, balance problems, risk of falls, and functional limitations may persist in the postoperative period.In addition, loss of performance may occur in daily tasks requiring motor-cognitive interaction (e.g., talking while walking, changing direction while carrying objects).The dual-task paradigm describes exercises and assessments that require the simultaneous execution of both motor and cognitive tasks; in rehabilitation, it aims to improve daily living functions by targeting the simultaneous functioning of motor and cognitive systems.In the literature, studies on dual-task assessment and training in individuals with knee osteoarthritis and TKA are limited, and the findings are heterogeneous. Studies in elderly and osteoarthritic populations have reported that both single-task and dual-task training improve balance performance, but dual-task training does not always show a clear superiority compared to single-task training. These studies have generally focused on balance and gait parameters; evidence on how other clinically important variables such as pain, reaction time, and fear of movement (kinesiophobia) change with dual-task interventions is insufficient and inconsistent.

Method: The effect size of the WOMAC Osteoarthritis Index assessment parameter in the reference article is 1.02. It was calculated that a minimum of 20 individuals in total, 10 in each group, were required for a study with 80% power, using a type I error of α=0.05 and a type II error of β=0.20.After obtaining informed consent from all participants, their sociodemographic information will be recorded. Subsequently, their cognitive status will be assessed using the Mini Mental State Test (MMSE).Pain will be assessed using the Numerical Pain Rating Scale (NPRS). Functional mobility will be assessed using the Timed Up and Go (TUG). Dynamic balance will be assessed using the Functional Reach Test. Static balance will be assessed using the Berg Balance Scale (BBS). Functionality will be assessed using the WOMAC Osteoarthritis Index. Kinesiophobia will be assessed using the Tampa Kinesiophobia Scale (TKS). Lower extremity reaction time will be assessed using the Fitlight Trainer (FITLIGHT Sports Corp., Ontario, Canada), a wireless system consisting of 8 sensors.Interventions: After participants were randomly divided into two groups, those in the control group would perform a physiotherapy program consisting of strengthening and balance exercises at home, provided by us, and would not participate in any other exercise program during the study period. Exercises would be taught to the control group in person by a physiotherapist at the time of the initial assessment, and follow-up sessions would be video-recorded. The intervention group's program would be a dual-task exercise program, in addition to the exercises provided in the home exercise program. Interventions would last for 8 weeks, 2 days a week, and the program would be updated weekly.

Inclusion Criteria:

• Mini Mental State Test score ≥24; ability to provide signed informed consent and voluntary agreement to participate in the study.
• Underwent primary unilateral total knee replacement surgery.
• Being between 50 and 65 years old

Exclusion Criteria:

• Having undergone revision or bilateral knee replacement surgery,
• Having experienced postoperative complications,
• Having undergone lower extremity surgery,
• Having a neurological disease.

Study Protocol and Statistical Analysis Plan