Those measurements were ascertained through the use of skin markers distributed on the lower extremities on subjects with no known histories of knee pathology or symptomatic complaints. After measuring VV and IRER angles in the neutral barefoot position, the researchers made similar measurements of those angles in several ski boot positions, including standing, canted, and rotated positions within the adjustable limitations of the ski boots. They also conducted measurements of simulated loading positions natural to skiing, achieved through the use of an angled platform duplicating the ski slope angle and a weighted pulley system designed to transmit downward forces between the skier and the sloped platform in the same perpendicular angle experienced during actual skiing. Critical Analysis of Technique Selected:

The technique selected provides an analysis of limited applicability to skiing because it tested only static forces rather than the many dynamic forces (both internal and external) associated with actual skiing. Less significantly, the researchers mentioned additional limitations on the accuracy obtainable through the use of skin markers, which are known to shift slightly, while pointing out that such movement is more of a concern when testing dynamic movements. Finally, local deformation of the ski boot materials under loading complicates the precision of markers measuring forces attributable to ski boot position. This limitation is likely greatly magnified under the dynamic stresses associated with skiing compared to the static loading measurable in the study as designed.

Greater precision would be possible through similar implementation of skin markers on subjects during actual...

Likewise, markers positioned on the ski boots themselves would enable researchers to minimize the imprecision due to the deformation of ski boot materials under loading.
Summary:

Skiing is an athletic activity known to be associated with a risk of knee injuries; specifically, the ACL is susceptible to acute rupture injuries and the typical ski position is known to alter the angular stresses applied to the patella causing increased grinding between its undersurface and the articular cartilage of the femoral epicondyle. In practical application, the research is more pertinent to traumatic ACL injuries than to chronic PFPS because the latter is not likely attributable to angular changes of short duration in comparison to the amount of time subjects spend in non-skiing postures.

The article disclosed statistically significant findings in the form of changes in the VV and IRER angles, which relate directly to decreased damage threshold in the ACL structure. Because the study measured only static loading in simulated ski postures, it likely underestimated the effects of those angular changes. Therefore, in spite of those methodological limitations, it is likely that the findings are still significant to skier, especially those with existing ACL issues from previous injuries, because the addition of dynamic forces associated with actual skiing can be assumed to increase rather than decrease their cumulative effect on the knee joint.