Clinic · 2 min read
The plumb line: how physios assess posture
The century-old side-view assessment Plumb is named after.
A 30-second assessment older than X-rays
Sometime in the early 20th century, physiotherapists settled on a side-view standing assessment that uses gravity as the reference. Hang a weighted string — a plumb line — past a relaxed person standing in profile. In ideal alignment the string passes, top to bottom: through the earlobe, midway through the shoulder, just behind the hip, just in front of the knee, and just in front of the ankle bone.
What deviations tell you
A forward head pushes the earlobe in front of the line. Rounded shoulders shift the shoulder joint forward. An anterior pelvic tilt rotates the pelvis ahead of the line. Each is normal in small amounts and meaningful when sustained — same logic as Nachemson and Hansraj: deviation × duration.
How Plumb uses this
The same logic adapted to a desk and a TrueDepth camera. Plumb watches the cervical and shoulder portion of the chain — the parts a front-facing camera can see honestly. The lumbar curve happens behind you; a future version of Plumb will include a back-worn sensor for that side of the chain.
Use the app, not just the score
A score of 95 with shallow breath and a tight jaw is not really 95. Plumb is a prompt to notice — not a verdict on how “correct” you are. The physio’s plumb line works the same way: a starting point, not a judgement.
Plumb is a wellness and posture-awareness tool, not a medical device. It doesn’t diagnose, treat, or monitor any condition. If anything about your body concerns you, see a qualified clinician.
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