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Analysis of Lower-Limb Muscle Synergies in Patients with Knee Osteoarthritis Before and After Physiotherapy Intervention

Mohammadi, Mohammad Reza | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58341 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Arjmand, Navid
  7. Abstract:
  8. Knee osteoarthritis is one of the most common musculoskeletal disorders, characterized by the gradual deterioration of the joint, reduced range of motion, chronic pain, and a decline in patients’ quality of life. This condition disrupts the neuromuscular system, leading to decreased motor coordination of the lower-limb muscles. The present study was designed to investigate the effects of a physiotherapy intervention on lower-limb muscle function as well as to analyze changes in muscle synergies in patients with knee osteoarthritis. Fourteen patients with moderate knee osteoarthritis were compared with eleven age-matched healthy individuals before and after undergoing physiotherapy treatment. The patients received a 10-session physiotherapy intervention including electrotherapy, infrared therapy, strengthening exercises, and stretching. Electromyography (EMG) data from eight lower-limb muscles, along with three-dimensional kinematic data, were recorded in movement tests, including walking at three different speeds (normal, slow, and fast) and the sit-to-stand test. All data were recorded in a motion analysis laboratory both before and after the intervention for the patient group and once for the healthy group. Kinematic data were used to identify the beginning and end of movement cycles, and EMG data were processed using appropriate filters. Synergy analysis was conducted using advanced dimensionality reduction algorithms, such as Non-Negative Matrix Factorization (NNMF), to evaluate changes in the number of modules, variance accounted for (VAF), stability index (SSI), and synergy coordination index (SCI) throughout the treatment period. Additionally, clinical measures, including VAS and the WOMAC, were used to assess pain, quality of life, and treatment effectiveness. The findings revealed that, before receiving the physiotherapy intervention, patients with knee osteoarthritis had fewer muscle synergies compared to healthy individuals (mean synergy count of pre-treatment: 2.43, post-treatment: 2.5 and healthy group: 2.82). No significant differences were observed in the SSI index between the two groups. However, significant differences were found in the SCI index and the VAF percentage (SCI: 0.099, 0.103, and 0.118 for pre-treatment, post-treatment, and healthy groups, respectively). This reduction indicates impaired muscle coordination and reduced complexity of motor control in these patients. After the intervention, significant improvements were observed in clinical indicators, including pain reduction (P-value <0.001) and quality of life (P-value = 0.007). However, the number of muscle synergies in the studied motor tasks did not significantly change before and after physiotherapy. A similar trend was observed for other indices, with the only significant difference before and after physiotherapy appearing in the SSI index during normal gait. Nevertheless, changes in several parameters indicated that the patients’ condition had moved closer to normal, and the significant difference between the pre-physiotherapy group and the healthy group disappeared after the treatment period. This study also examined the activity of individual muscles within each synergy module, revealing more significant differences in muscle activity patterns during fast gait
  9. Keywords:
  10. Muscle Synergy ; Electromyography ; Rehabilitation ; Osteoarthritis ; Physiotherapy ; Human Movment Analysis ; Knee Osteoarthritis

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