Failed Load Transfer Explorer
In quiet standing the person offloads one leg and reloads it; the sacroiliac joint should self-lock as load crosses it. This page asks the questions that matter for the test: when the joint fails, is it on the side that walks well passively (IPC A), or on the side locked in a phase of gait (IPC B, C or D)? Then refine by sex, age, leg-length discrepancy, site and complaint side, and ask whether the failing side is the painful side. Subjects not assessed for FLT are excluded throughout.
When the joint fails, which side fails — the optimal side or the impaired side?
People with a single unilateral failure, one IPC A side and one impaired (B, C or D) side on the other leg. Bilateral failures and bilateral gait grades are set aside, because there the question has no answer.
Split by which grade the impaired leg carries
When a leg is locked in a phase of gait, is FLT more likely to be present at all?
Share failing to self-lock, by passive gait profile, discrepancy band and sex — with the whole population in view as the reference line.
By passive gait profile
By leg-length discrepancy
By sex
Left or right?
Laterality of the failure itself, among people who failed on one side only.
Does the failing side match the side of the pain?
The side the person complained of (Data2020 column I) against the side that failed to lock. Where both are one-sided, do they agree — and when they do not, is the pain on the leg that walks well or the leg that is locked?
Failing side × complaint side
Agreement by site of complaint
Where the pain sits when the gait picture is one-sided
People with one-sided pain, one IPC A leg and one impaired leg. Dark bar = pain on the IPC A (optimal) side; gold bar = pain on the impaired side. The last row asks the same of the failing side, for people who also failed on one side only.
What the failing leg was doing in gait, against what the other leg was doing
Every unilateral failure in view, grouped by the IPC grades on the failing side and on the opposite side. A “–” means no grade was recorded for that leg.
How to read this — honestly
The failure rate is not a prevalence. FLT has a result for 131 of 572 people in the cohort; the other 441 were never assessed and are excluded from every number on this page. Of those assessed, failed — a ceiling that says more about who was tested than about the joint. FLT was most often recorded when it was found. So Question 2 cannot be answered from this data, and the panel says so; it is kept on the page so the negatives stay visible.
The side question is different. Given that a person failed on one side, which side it was is a fair comparison — both legs were assessed in the same person at the same moment, so recruitment does not bias it. That is why Question 1 carries the weight here.
Small groups, unadjusted p-values. Binomial tests compare a split against 50:50; Fisher tests compare two proportions. Nothing is corrected for multiple comparisons, so one result under 0.05 by chance is expected across a page like this. Read anything under about n = 20 as pattern-spotting.
Grades. IPC A is the leg that works optimally on passive assessment of gait; B is a leg locked in midstance, C locked in heel-off (the long side), D locked in heel strike (the short side). A person can carry more than one grade.
What would make this conclusive
Record FLT on everyone. 441 people carry “did not assess”. A consecutive series with the negatives written down would turn Question 2 from unanswerable into answered, and would let the failure rate stand as a prevalence.
Test the side finding against handedness and footedness. Those columns are largely empty, and they are the obvious rival explanation for any lateral bias.
Pair the DUSI imaging with the clinical test. Even fifteen to twenty imaged subjects matched to their result would support a claim about criterion validity — firmer ground than any association on this page.