A broad range of disorders, including cerebral palsy, osteoarthritis, stroke, spinal cord injury, and Parkinson’s, can limit mobility.  Computer modeling and simulation, enabled by OpenSim, allows researchers and clinicians to uncover the mechanisms that underlie movement disorders and design effective treatments, like strengthening exercises or gait retraining.

Smarter Rehab: How much muscle strength is required to walk in a crouch gait?


Cerebral palsy is a neurological disorder that affects muscle control during movement, and consequently leads to a variety of pathological gait patterns. One common movement pattern is called crouch gait, defined as excess flexion or bending of the knee joint during walking. One hypothesis for why children walk in crouch gait is that the muscles responsible for extending the knee joint are weak. Katherine Steele of Stanford University and Marjolein van der Krogt of the VU University Medical Center are using OpenSim to understand how much muscle strength is needed to walk in a crouch gait as compared to an unimpaired gait.

The research team used OpenSim to generate simulations of gait for three unimpaired children and nine children who walked in a crouch gait. They tested weakening the major muscle groups in the lower leg. Each muscle group was successively weakened until the model was no longer able to track a subject’s gait kinematics.

Surprisingly, subjects were able to compensate for weakness of all the major leg muscles by increasing the activation of synergistic muscles that performed the same function. They also found that walking in a crouch gait was possible with greater weakness of the gluteus medius, a hip extensor muscle, and the plantar flexors or calf muscles. This suggests that crouch gait might be a compensation for gluteus medius or plantar flexor weakness and that these muscles would be good candidates for strength training.

Visit Steele and van der Krogt’s project on to find out more:

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Subject specific simulations of Stroke Gait

Jill Higginson
University of Delaware

SImulating crouch gait in children with cerebral palsy

Katherine Steele
Stanford University

Strength and crouch gait

Katherine Steele
Stanford University
Marjolein van der Krogt
VU University Medical Center

Grand challenge to predict in vivo knee loads

BJ Fregly
University of Florida

Upper Extremity Model

Katherine Holzbaur
Wake Forest University
Wendy Murray
Northwestern University

A Lower Extremity Model for Human Movement Analysis

Edith Arnold
Stanford University

London Lower Limb Model

Luca Modenese and Andrew Phillips
Imperial College London

A Musculoskeletal Model of the Lumbar Spine

Nur Adila Faruk Senan
University of California, Berkeley

Simulations of Walking at Multiple Speeds

May Liu
Stanford University

A Detailed Musculoskeletal Model of the Hip

Kevin Shelburne
University of Denver