What it means
The pelvis in front of the ribcage with a flat low back and a long thoracic hump.
Where it comes from
The habit of standing on ligaments rather than muscles, shifting the centre of mass.
How it is measured
It is measured on the side view, in the sagittal plane. The defining measurement is Trunk leans (Sagittal trunk inclination), and it is reported as a finding from above 3°. 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 3° | Within normal range |
| 3–6° | Mild sway back |
| 6–10° | Moderate sway back |
| 10° and above | Severe sway back |
Source of the bands: Kendall FP et al, Muscles: Testing and Function with Posture and Pain, 5th ed
What is usually seen alongside it
- Pelvis tipped forward or back (Sagittal pelvic tilt) — below undefined°
- Sway back (Lumbar lordosis) — below 25°
- Rounded upper back (Thoracic kyphosis) — above 45°
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
From the side, a sway back carries the pelvis forward of the ankle and the thorax back behind it; a flat back has no such translation.
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 sway back reported?
When trunk leans (sagittal trunk inclination) is above 3°, it is reported as a finding. That is where the "Mild sway back" band begins. The bands come from: Kendall FP et al, Muscles: Testing and Function with Posture and Pain, 5th ed
Can sway 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. From the side, a sway back carries the pelvis forward of the ankle and the thorax back behind it; a flat back has no such translation.
What is the most severe grade?
The worst band in this table is "Severe sway back". The grade is printed beside the measurement itself in the report, so it is always clear which number produced the word.