This study, including two time points, is performed to determine validity and reliability of performance based assessments using a one-arm sample.

A test retest design is used to determine reliability and a cross-sectional design to determine validity.

For each participant, the measures will be performed on two time points with a minimal recovery break of 2 days in one single centre in the Canton of Zurich (University Hospital Zurich).

This study evaluates the reliability (Test-Retest) of six health related instruments that assess physical function in people with hemophilia: Short Physical Performance Battery, Unipedal Stance Test, Four Square Step Test, Timed up and Go, 1 kg Arm Lift Test, 30 Second Chair Stand Test. This study is needed to determine the psychometric properties of these six assessments. Validity of these test will be determined with the Short Form 36, the Hemophilia Activities List and the Hemophilia Joint Health Score Methodology: Reliability (Test re-test study and validity (cross sectional study) of the six tests reported in patients with hemophilia.

This intervention contains physiotherapie assessments, however, no drugs nor medical devices.

SPPB comprises three components: Standing balance (open stand, half tandem stand and tandem stand), timed four meter usual paced walk, and timed test of five sit-to-stands from a standard chair. Each component is scored from 0 to 4, with maximum of 12and timed test of five sit-to-stands from a standard chair.

The FSST is a performance-based outcome measure assessing dynamic balance. The test set up consists of four walking sticks of the same width in a cross formation. Participants step into each square in a clockwise sequence and back anticlockwise as fast as possible while not being allowed to hit the sticks.

The TUG is a performance-based outcome measure that assesses lower extremity function, mobility, and fall risk. In this test, the participant starts in a seated position, with his back against a standard height chair, without armrest. The participant gets up and walks in a comfortable pace for 10 feet (three meters), turns around and returns to a seated position in the chair. The time to perform the task is measured in seconds. Shorter time indicates better mobility.

The UST is a balance assessment that is widely used in clinical settings to monitor neurological and musculoskeletal conditions. Abnormal values may indicate conditions that may impair balance and will quantify balance status for those who are at increased risks for fall. The test is performed barefoot, hands crossed over the chest and once with eyes open and once with eyes closed. Patient stands on one leg unassisted; time begins when opposite foot leaves the ground. Time stops immediately when arms are uncrossed, the raised foot is used to maintain balance or touches the ground, weight-baring foot is moved, 45 second have elapsed or when eyes were opened on eyes closed trial. Each condition (eyes open or eyes closed) is performed three times, alternatively.

The Short Form 36 is a generic health related quality of life instrument consisting of 36 items pertaining to eight dimensions ('physical functioning', 'role physical functioning', 'bodily pain', 'general health perception', 'vitality', 'social functioning', 'role emotional functioning' and 'mental health'. The possible score ranges from 0 to 100 points, with 0 points representing the greatest possible health restriction, while 100 points indicate no health restriction.

In addition, each item is scored on a 0 to 100 range so that the lowest and highest possible scores are 0 and 100, respectively.