Static vs. Dynamic: How Markerless Motion Capture Captures Knee Alignment in OA

August 19, 2025
Theia
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Summary

A new peer-reviewed study from Queen's University and Kingston Health Sciences Center has shown how markerless motion capture can quantify lower limb alignment in study participants with knee osteoarthritis, without the limitations of traditional marker-based systems.

Editor's Note: The following summary details independent academic research conducted in clinical research settings. Theia3D is an offline software solution engineered exclusively for research and human performance analysis.

Why Lower Limb Alignment Matters in Knee OA Research


Frontal plane lower limb alignment is a key factor in assessing severity and informing research decision-making related to knee osteoarthritis. Varus or valgus malalignment can accelerate disease progression and influence research protocols.

Current standard: Long-leg radiographs are used to measure alignment, but these have limitations including radiation exposure, inconsistent limb positioning, and being static only — missing how alignment changes under load during gait.

Study Overview
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Objectives:

  1. Quantify static and dynamic lower limb alignment in study participants with advanced medial or lateral knee OA.
  2. Examine sex differences in alignment.
  3. Explore correlation between static (quiet standing) and dynamic (gait) alignment.

Participants: 92 study participants (37 male, 55 female) with advanced knee OA (Kellgren-Lawrence grade 3+)

Methods: Eight synchronized video cameras processed in Theia3D, measuring frontal plane knee adduction angle during quiet standing and walking.

Key Findings

  1. Clear Separation Between Medial and Lateral OA — Medial OA averaged +3.1° varus in quiet standing; lateral OA averaged -4.3° valgus (p<0.001)
  2. Sex Differences — Males were more varus than females in both static and dynamic tasks (p<0.01).
  3. Strong Static-Dynamic Correlation — Spearman’s ρ = 0.86 (p<0.0001). Study participants were 2.6° more varus during gait compared to quiet standing on average.
  4. Research Insight — Dynamic gait assessment revealed greater malalignment than static measures.

Why This Matters for Researchers
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  • Dynamic alignment assessment may capture functional deficits that static X-rays miss.
  • Markerless systems can be integrated into research lab workflows with minimal setup.
  • Potential for radiation-free, repeatable, and real-world assessments to inform future research directions.

Read the full peer-reviewed study here.
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Curious what these findings could mean for your lab? Book a free Quick Consult with our biomechanics team to explore how markerless motion capture can fit into your workflows →
Recent Posts
A Major Research Milestone for Theia3D
More than 50 independent, peer-reviewed research publications now cite, evaluate or review Theia3D across domains including gait, sports performance, postural control, upper-extremity movement and other biomechanics applications. These publications are available in world-leading journals including Journal of Biomechanics, Journal of Applied Biomechanics, Gait & Posture and Clinical Biomechanics. Together, they represent a growing body of evidence across different movements, populations and environments, reinforcing Theia3D’s position as the most extensively validated markerless motion capture system.
Beyond The Radar Gun: How Dean Jackson uses Theia3D For Incremental Velocity Analysis
This article is a first in a miniseries that breaks down what motion capture can show beyond radar, ball data, and standard video. In this first installment, Dean breaks down how he uses Incremental Velocity Analysis, or IVA, to study what changes biomechanically as pitchers move closer and closer to max output.
New Research on Theia3D: Comparing Markerless and Marker-Based Shoulder Kinematics Across Full Arm Range of Motion
A 2025 study published in the Journal of Biomechanics compared shoulder kinematics measured with Theia3D markerless motion capture against gold-standard marker-based motion capture across full arm ranges of motion. The results show strong agreement for many movements, particularly in the coronal plane, while also highlighting where caution is still required, especially at the extremes of ranges of motion and in transverse-plane rotations.
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Summary