Enter the pain score, weight-bearing score, stiffness score, and activity limitation score into the calculator to determine the Foot Function Index.

## Foot Function Index Formula

The following formula is used to calculate the Foot Function Index (FFI).

FFI = (P * W * S * A) / 100

Variables:

- FFI is the Foot Function Index (%)
- P is the pain score (0-100)
- W is the weight-bearing score (0-100)
- S is the stiffness score (0-100)
- A is the activity limitation score (0-100)

To calculate the Foot Function Index, multiply the pain score, the weight-bearing score, the stiffness score, and the activity limitation score. Then divide the result by 100. The Foot Function Index is expressed as a percentage, with higher values indicating worse foot function.

## What is a Foot Function Index?

The Foot Function Index (FFI) is a self-reported questionnaire used to measure the impact of foot pathology on function in terms of pain, disability, and activity restriction. It is commonly used in clinical and research settings to assess the severity of conditions such as arthritis, foot injuries, or deformities, and to monitor changes over time or in response to treatment. The FFI consists of 23 items divided into three subscales: pain, disability, and activity limitation.

## How to Calculate Foot Function Index?

The following steps outline how to calculate the Foot Function Index (FFI).

- First, determine the pain score (P) ranging from 0 to 100.
- Next, determine the weight-bearing score (W) ranging from 0 to 100.
- Next, determine the stiffness score (S) ranging from 0 to 100.
- Next, determine the activity limitation score (A) ranging from 0 to 100.
- Finally, use the formula FFI = (P * W * S * A) / 100 to calculate the Foot Function Index.
- After inserting the values for P, W, S, and A into the formula, calculate the result.

**Example Problem:**

Use the following variables as an example problem to test your knowledge:

Pain score (P) = 80

Weight-bearing score (W) = 90

Stiffness score (S) = 70

Activity limitation score (A) = 85