IMU Gait Analysis in Dogs: What Gyroscope Data Can Tell Us About Movement
When observing a dog walking, we first tend to notice the overall picture. Is the dog moving evenly? Is there a visible lameness? Is one step shortened, or is one limb being unloaded? But a gait cycle involves much more than simply moving forward.
With every step, limbs accelerate and decelerate, joints flex and extend, and individual body segments move and rotate in space. Many of these processes take place within fractions of a second and can only be quantified to a limited extent by the human eye.
This is where IMU gait analysis in dogs comes into play. Inertial sensors make it possible not only to observe movement, but also to measure and objectively evaluate it. The integrated gyroscopes play a particularly interesting role in this process.
They add another perspective to gait assessment: it is not only about how far or how fast a dog moves, but how the dog moves.
What happens during a single step?
At first glance, a step appears simple: a paw makes contact with the ground, the limb bears weight, the paw leaves the ground again and the limb moves forward. Biomechanically, however, much more is happening. The individual segments of the limb continuously change their position and orientation. Joints move through flexion and extension, the limb accelerates and decelerates, and the interaction between the forelimbs and hindlimbs contributes to the movement and stability of the entire body. Functional limitations can therefore affect very different aspects of the gait pattern. A dog may, for example, alter its stance phase, shorten a step or change the way a particular body segment moves. To assess these changes in a differentiated way, a single measurement is not enough.
What are IMU sensors?
IMU stands for Inertial Measurement Unit. These compact sensors can capture different types of movement information and are used in movement analysis in both humans and animals. One important component of an IMU is the accelerometer. It measures linear acceleration along different spatial axes. A gyroscope, in contrast, measures angular velocity. In simple terms, angular velocity describes how quickly the body segment to which the sensor is attached rotates around a particular axis. This distinction is important: a gyroscope does not directly measure a joint angle, range of motion or movement restriction. It initially records rotational movement, or more precisely its angular velocity.
Only through our algorithmic processing of the sensor data can further information about the movement pattern be derived.
Acceleration and rotation provide different information
In simplified terms, the two measurement principles can be distinguished as follows:
Accelerometer = linear acceleration
Gyroscope = angular velocity / rotation
Both signals describe different aspects of the same movement. Considering them together enables a more differentiated kinematic analysis than looking at a single sensor signal alone.
Why is gyroscope data interesting for gait analysis?
A dog does not simply move from point A to point B when walking. Even if a limb appears to move forward relatively evenly from the outside, numerous rotations occur throughout this movement. Joints flex and extend, body segments change their orientation, and the direction of movement of individual segments changes continuously throughout the gait cycle. It is precisely this dynamic aspect of movement that makes gyroscope data particularly interesting for kinematic gait analysis in dogs.
They broaden the analysis to include a key question: How is the movement actually performed?
LupoGait therefore examines various aspects of movement together. The LupoGait Manager visualizes a total of 34 biomechanical parameters. These include, among others, stance and swing phases, stride length, symmetry, range of motion, as well as parameters related to flexion, extension, acceleration, and rotation. No single value is decisive here. Only the interplay of various parameters makes it possible to describe an individual movement pattern in a nuanced way.
What does a gyroscope measure?
A gyroscope measures angular velocity around its measurement axes. It therefore captures rotational movements of the body segment to which the sensor is attached. Importantly, joint angles, range of motion and other kinematic parameters should not be confused with the direct measurement signal of a gyroscope. Such parameters can be derived through the processing and combination of different sensor data.
When two steps look the same but are not the same
This is an important aspect of objective gait analysis. Two movement patterns may initially appear very similar to the human eye. However, this does not necessarily mean that the underlying kinematics are identical. Dogs can modify their movement and compensate for functional limitations without immediately developing an obvious visible lameness. Instead, changes may become apparent in different aspects of the overall movement pattern. An abnormal gyroscope, symmetry or ROM value on its own is therefore not a diagnosis. What matters is the context:
- Which limb shows a change?
- Which other parameters have changed?
- Are there differences between the left and right sides?
- How does the movement pattern develop across several examinations, and do the measured changes correspond with the findings of the clinical examination?
Objective gait analysis does not replace the veterinary examination. It complements it by adding a measurable functional perspective.
The advantage of wearable IMU sensors
One key advantage of wearable IMU sensors is that the sensors move with the patient. This fundamentally distinguishes the measurement principle from methods in which movement information is captured exclusively within a stationary measurement environment. With a mobile sensor system, kinematic analysis is not inherently restricted to a fixed measurement location. For a standard LupoGait measurement, a standardised straight track is used first. Defined conditions are important, particularly for follow-up assessments, where measurements should be performed under conditions that are as comparable as possible. Mobility, however, creates additional possibilities. Depending on the clinical question, movement can also be assessed on different surfaces or during additional movement tasks such as circles and turns. This can be relevant because functional abnormalities may not become equally apparent under every condition.
Standardisation and mobility are not contradictory
Standardised and variable measurements serve different purposes. A standardised straight-line measurement provides a reproducible basis and facilitates comparison between different measurement points over time. Additional measurement situations, on the other hand, can be used to investigate a specific functional question. Standardise when comparability is required. Vary the conditions when the clinical question calls for it. This is one of the strengths of mobile gait analysis: the sensors remain on the patient while the conditions can be adapted to the specific question being investigated.
From gyroscope data to a movement pattern
Ultimately, objective gait analysis is not about producing as many numbers as possible. Each parameter describes only one aspect of a complex movement pattern. Stance phase, swing phase, stride length, symmetry, range of motion, acceleration and rotational parameters each answer different questions. The real value emerges when this information is considered together.
Individual measurements can then form a movement profile that complements clinical observations, objectively quantifies differences and documents changes across multiple measurement sessions. The gyroscope itself is only one component of an IMU sensor. However, it provides a particularly interesting piece of information for movement analysis: the angular velocity of a moving body segment. Because in modern gait analysis, the question is not only:
How far does the dog move?
But rather: How does the dog move?
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