Can a smartphone camera measure chronic pain's impact on movement?

Chronic pain reduces function, but measuring this objectively outside clinics is hard—optical motion capture is expensive and lab-only. This work builds QMT, a smartphone video pipeline using deep learning to extract 3D body kinematics. Validated against gold-standard motion capture (r > 0.85 correlation), it tracked fibromyalgia and sciatica patients over weeks, detecting group differences from home video alone. More variance at home than lab, but it works; opens the door to scalable, remote tracking of movement quality in clinical trials.