Knee IMU Angle Plotter

Plots the 3 relative joint angles (pitch, roll, yaw) from two IMUs placed on the thigh and shin, recorded during squat movements. Outputs a 3-panel time-series chart showing the primary flexion/extension angle and the two minor angles.

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Requirements

• Python 3.9+
• pip

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Setup

1. Clone or download this project, then open a terminal in the project folder.

2. Create a virtual environment:

python3 -m venv venv

3. Activate the virtual environment:

# Mac / Linux
source venv/bin/activate

# Windows
venv\Scripts\activate

You should see (venv) appear at the start of your terminal prompt.

4. Install dependencies:

pip install -r requirements.txt

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Usage

Basic — opens an interactive plot window:

python plot_knee_angles.py your_data.csv

Save the plot to a file instead:

python plot_knee_angles.py your_data.csv output.png

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CSV Format

The script expects a CSV file with the following columns:

Column	Description
timestamp	Time in milliseconds
pitch	Flexion/extension angle (degrees)
roll	Varus/valgus angle (degrees)
yaw	Internal/external rotation (degrees)
seq	Sequence number (optional)
flex	Flex flag (optional)

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Configuration

At the top of plot_knee_angles.py you can adjust:

Variable	Default	Description
SMOOTHING_WINDOW	5	Rolling average window in samples. Set to 1 to show raw data only.
FIGURE_SIZE	(14, 9)	Width and height of the figure in inches
PRIMARY_COLOR	blue	Colour for pitch (flexion) panel
SECONDARY_COLOR	green	Colour for roll panel
TERTIARY_COLOR	red	Colour for yaw panel
ALPHA_RAW	0.25	Opacity of the raw data line

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Deactivating the virtual environment

When you're done:

deactivate