Investigating the effects of center of rotation of angulation (CORA) location on varus knee joint mechanics

Articles in Press

Document Type : RESEARCH PAPER

Authors

School of Mechanical Engineering, University of Tehran, Tehran, Iran

10.22038/abjs.2025.86203.3924

Abstract

Objectives: This study investigates the significance of CORA (Center of Rotation of Angulation) in modeling the biomechanics of lower limb joints and its possible contribution to such skeletal abnormalities as varus deformity which would negatively affect one’s ability to move normally. Methods: An improved computational model of the lower limb joints is proposed which incorporates the accurate location of CORA on the bone. The improved model enables the prediction of kinetics and kinematics behavior of the lower limb joints. To demonstrate the applicability of the proposed approach, multiple inverse kinematics and dynamics simulations were carried out for a 10-degree varus deformity wherein the CORA position was varied from 1/6 to 5/6 of the femur length measured from the hip to knee joint, along with a baseline model of normal lower limb alignment. Results: The simulated experiments showed that varus deformity has a small effect on the subtalar angle but strongly influenced the subtalar moment during the stance phase. When the CORA was placed closer to the hip joint, there was an increase in ankle plantar/dorsiflexion and knee extension/flexion angles. Also, proximal CORA location affected joint reaction force in the ankle and hip joint, resulting in an increase and decrease, respectively. Although hip abduction/adduction moments showed only slight changes, hip rotation moments varied significantly for different CORA locations, particularly in the stance phase. Conclusions: Using CORA in modeling helps create accurate simulations of deformities and offers detailed information about joint kinetics and kinematics. This knowledge can help surgeons better understand the patient’s condition and make a more precise surgical plan.

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The Archives of Bone and Joint Surgery

Articles in Press, Accepted Manuscript
Available Online from 03 November 2025

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History

  • Receive Date: 22 February 2025
  • Revise Date: 15 October 2025
  • Accept Date: 19 August 2025

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