Validity and Reliability of the Figure-of-Eight Walking and Weight-Bearing Lunge Tests in Hemophilia

Recurrent joint bleeding (hemarthrosis) occurs in 70-80% of cases of hemophilia. The three most frequently affected joints are the synovial joints of the ankle, knee, and elbow. Among these, the ankle and knee are the most common sites of bleeding, accounting for 80% of cases (Stephensen et al., 2009). This susceptibility stems from factors such as the fact that the knee and ankle are weight-bearing joints and are highly exposed to trauma.

Hemophilia treatment aims to reduce the frequency of bleeding episodes through prophylactic factor replacement; however, joint bleeding can recur despite treatment, potentially leading to permanent joint damage. This joint disease causes pain, reduced range of motion, and potential impairment of postural balance, while also increasing the risk of falls.

Due to its complexity and significance for the individual, gait assessment is a crucial component in evaluating mobility, functional capacity, and rehabilitation progress across various populations, including the elderly, individuals with neurological disorders, and those recovering from injuries. Various clinical tests and technological tools are available to measure different aspects of gait, such as walking ability, endurance, adaptability, and fatigue. Timed walking tests-such as the Timed Up and Go (TUG) test, the 2-Minute Walk Test (2MWT), the 6-Minute Walk Test (6MWT), the 10-Meter Walk Test (10MWT), and the Timed 25-Foot Walk Test (T25FW)-measure gait speed, endurance, and overall walking ability. A common feature of these tests is that they involve walking along a straight path with little to no change in direction; while this makes them effective in standardized clinical settings, they are relatively less suitable for assessing the complex mobility demands of daily life. In contrast, the Figure-8 Walk Test (F8WT) requires continuous changes in direction and turning, thereby challenging anticipatory postural adjustments, spatial navigation, and motor planning. Literature has demonstrated that walking along a curved path challenges dynamic balance and increases gait variability, revealing deficits-particularly in the elderly and in individuals with neurological or cognitive impairments-that are not apparent during straight-line walking.

In their daily lives, people frequently encounter curved paths and changes in walking direction-such as walking around a table, turning a corner, or avoiding an obstacle. The ability to successfully adapt one's gait and safely execute turns or changes in direction is fundamental to an individual's mobility and independence.

The Timed Up and Go (TUG) test is a widely used, performance-based clinical assessment tool for measuring lower-extremity function, mobility, and fall risk in individuals; its reliability and validity are well-established. The ABC scale is a 16-item measure used to assess balance confidence while performing specific activities both indoors and outdoors; it has also been proven reliable and valid. Among older adults, a score of 76% or lower indicates a risk of falling. The Weight-Bearing Lunge Test (WBLT), which assesses ankle dorsiflexion mobility, has demonstrated excellent test-retest reliability in patients with hemophilia, even in those with limited joint damage. Another test that is reliable and shows strong correlation with other functional measures in individuals with hemophilia is the Four Square Step Test (FSST). The FSST is associated with age rather than the severity of hemophilia and provides clinicians with information regarding the speed and ability to change direction and step over obstacles. The Y Balance Test (YBT) is a dynamic balance and postural control assessment that is increasingly preferred for use with patients with hemophilia in recent years.

Since the F8WT requires continuous changes of direction, it demands greater dynamic balance, spatial planning, and gait adaptation. It is important to examine the validity and reliability of the F8WT-which assesses change of direction, dynamic balance, agility, and functional mobility-in patients with hemophilia. The fact that the F8WT is easy to administer, quick to complete, and requires minimal equipment offers significant advantages for clinical use. However, no study evaluating the psychometric properties of this test in patients with hemophilia has been found in the literature. The aim of this study is to investigate the test-retest reliability and construct validity of the F8WT and WBLT in adult patients with hemophilia.