What it means
A low back with no natural curve, tiring quickly on standing.
Where it comes from
A posterior pelvic tilt from short hamstrings with weak back extensors.
How it is measured
It is measured on the side view, in the sagittal plane. The defining measurement is Sway back (Lumbar lordosis), and it is reported as a finding from below 20°. The number is computed from landmarks on that photograph — not estimated by eye, and not compared against a stock example.
What the numbers mean
| Measurement | Grade |
|---|---|
| up to undefined° | Within normal range |
| undefined–undefined° | Mildly flattened |
| undefined–undefined° | Moderately flattened |
| undefined–undefined° | Severely flattened |
Source of the bands: Conventional 20-45° lumbar window; surface measurement
What is usually seen alongside it
- Pelvis tipped forward or back (Sagittal pelvic tilt) — below undefined°
None of these is a diagnosis on its own. Together they corroborate the finding; apart, they do not refute it — a measurement nobody took counts neither for nor against.
What confirms it
Short hamstrings rotate the pelvis backwards; the popliteal angle and the straight-leg raise measure that.
Every number on this page is measured on the skin surface in a photograph. That is not the same as a measurement taken on a radiograph: it correlates with one and does not replace it. Wherever the decision depends on imaging, this page and the report itself say so.
What happens at the clinic
The assessment starts with three standing photographs — front, side and back. Every angle is measured on those photographs, the report prints the number and the grade for each, and the exercise programme is built from those numbers rather than from a template. Posture analysis explains the whole path, and the online assessment can be started from your own photograph now.
Frequently asked questions
At what point is flat back reported?
When sway back (lumbar lordosis) is below 20°, it is reported as a finding. That is where the "Mildly flattened" band begins. The bands come from: Conventional 20-45° lumbar window; surface measurement
Can flat back be assessed from a photograph?
A photograph gives a number, which most assessments do not have. But it is a surface measurement and it does not replace imaging. Short hamstrings rotate the pelvis backwards; the popliteal angle and the straight-leg raise measure that.
What is the most severe grade?
The worst band in this table is "Severely flattened". The grade is printed beside the measurement itself in the report, so it is always clear which number produced the word.