OPI: Scoring a Movement Session
The Overall Performance Index summarizes a session as a 0-100 score built from five measured domains, and keeps those domains visible next to the total.
A recorded session produces a very large amount of kinematic data. Raw signals are useful for close analysis, but the first clinical question is simpler: how did this session go compared to the ones before it? Answering that from raw curves takes time a working clinician usually does not have.
TropX answers it with the Overall Performance Index. OPI is a 0 to 100 score for the session, with a letter grade from A to F, computed from the measured kinematics of every rep.
Five domains, visible at all times
OPI is built from five separately scored domains: range of motion, velocity, explosiveness, smoothness, and left/right sync. The domain scores are always displayed next to the total. A session can score 86 overall while showing velocity at 73 and sync at 99, and the clinician sees that composition immediately.
The decomposition is what keeps the score useful. Each domain traces back to the per-rep metrics it was computed from, so a low domain score is the start of an inspection instead of a dead end.
Where the score is used
Every session card in the app carries its OPI and grade, so a week of sessions can be read at a glance. The progress view plots scores and individual metrics across sessions, where trends and plateaus become visible early.
Across a caseload, the same score is used for ranking. A patient whose sessions are trending down stands out on the board before anyone has re-read a report.
A summary score is only as good as the measurement underneath it. OPI sits on directly measured joint kinematics from two sensors per leg, which is why we are comfortable putting a single number on a session.