Total knee arthroplasty (TKA) is a cost-effective treatment for end-stage knee osteoarthritis. It has demonstrable benefits such as reducing pain and improving activity and quality of life. Despite the decrease in pain after surgery, the expectations of patients regarding their physical functions are not fully realized. Physical performance tests and reporting tests are used to objectively evaluate physical function and reveal the patient's condition. It is known that physical performance tests better reflect post-surgical changes. In addition, it has been stated that there may be serious differences between the results of the reports based tests and the actual functional capacities of the patients. The 2-minute walk test and the 6-minute walk test are tests that are used in the evaluation of lower extremity physical performance and have been shown to be valid and reliable in different populations. However, a certain length of corridor is needed in order to carry out these timed walking tests. As an alternative to these, another test used in the evaluation of physical performance is the 2-minute step test. This test, which was developed in 1999, does not require much equipment and space, so the test can be easily applied in any environment. In this test, a height specific to each individual is determined (as high from the ground as the distance between the Spina iliaca anterior superior and the midpoint of the patella), and the participant is asked to raise and lower both knees, respectively, to this height for 2 minutes. These tests used in the evaluation of patients should be valid, reliable and sensitive. In clinical studies, reliability is an important psychometric property. Because stable data are necessary to provide accurate data on treatment effects or the amount of change observed over time. Another important psychometric property is validity. Validity is defined as the degree to which a concept is accurately measured in a quantitative study. Reliability studies of the 2-minute step test in active and sedentary lean adults have been conducted, but the psychometric evaluations necessary for its routine use in patients with TDP have not been performed.

This study is a non-experimental, descriptive methodological study. Forty-nine patients who applied to the outpatient clinic of Kütahya Health Sciences University, Evliya Çelebi Training and Research Hospital due to knee osteoarthritis, will included in the study. Pre-study power analysis was performed and the power to detect clinically significant difference was calculated as 90% (5% Type I error level). The smallest sample size to be taken was determined by using the sample size creation section in the G-Power (version 3.0.10) program.

Inclusion Criteria:

• Being 18 years or older
• Having been diagnosed with knee OA by an orthopedic specialist and having a knee prosthesis applied.

Exclusion Criteria:

• Those who do not understand verbal and written information in Turkish
• Patients who underwent complex surgery requiring bone grafting
• Those with orthopedic or neurological disease causing gait disturbance
• Those with pain of 5 or more on the numerical pain scale
• Those with a history of Myocardial Infarction
• Those who have undergone surgery in the last 6 months
• Those with concomitant heart failure
• Those with unstable angina
• Those with uncontrolled hypertension
• Those with severe COPD, Asthma and Interstitial Lung Disease

Patients who have undergone total knee replacement surgery with age of older than 18.