The bent knee fall-out (BKFO) test (reproduced with permission from Movement Performance Solutions). The BKFO test was used to test the ability to prevent rotation of the lumbar spine during abduction/lateral rotation (bent knee fall-out) of the hip. The test was classified as a low-load (threshold) test. Photos illustrates examples of views during the test. Start position: The subject lay supine with both legs straight. A pressure biofeedback unit (Chattanooga Group, Hixon, TN) was positioned between the lumbar lordosis and bench ipsilaterally to the test side and inflated to a pressure of 40 mmHg. A folded towel (towel thickness adjusted to match the height of the biofeedback unit) was placed between lumbar lordosis and bench on the contralateral side. The subject then flexed the hip and knee on the side to be tested until the foot was in line with the contralateral knee. Lumbar position was corrected (if needed) so that the biofeedback unit was 40 mmHg. Test movement: While preventing the lumbar spine from rotating, the subject lowered the bent leg out to the side, to 45° abduction/lateral rotation (bent knee fall-out) and then returned to the starting position. Criteria: Pass: ≤ 4 mmHg away from the initiating 40 mmHg during bent knee fall out.
Monnier et al. BMC Musculoskeletal Disorders 2012 13:263 doi:10.1186/1471-2474-13-263