> ## Documentation Index
> Fetch the complete documentation index at: https://docs.uplift.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Loading Phase Max Knee Flexion

> Maximum knee flexion of the front leg and back leg during the loading phase of the serve.

<img src="https://mintcdn.com/upliftlabs/Ku7T6jLWrJyoK7uq/biomechanics/activities/tennis/images/knee-flexion.png?fit=max&auto=format&n=Ku7T6jLWrJyoK7uq&q=85&s=7cc97eb92c8668f0c179ed64fbf4e4a2" alt="Knee flexion during loading phase" width="500" height="500" data-path="biomechanics/activities/tennis/images/knee-flexion.png" />

## Technical Details

* **Variable Type:** Discrete Metric
* **Data Type:** Float
* **Units:** degrees (°)
* **Column Name:** `loading_phase_max_front_knee_flexion`, `loading_phase_max_back_knee_flexion`
* **Measurement:** Maximum knee flexion angle during the loading phase ([Ball Release](/biomechanics/activities/tennis/events/ball-release) to [Low Arm](/biomechanics/activities/tennis/events/low-arm))

## Description

This metric captures the maximum knee flexion achieved by each leg during the loading phase of the serve.
Greater flexion can indicate more lower-body drive and a higher jump.

Metrics are reported separately for front and back leg.

## Use Cases

* Lower-body loading and drive
* Stance and technique comparison
* Consistency across trials