Objective To explore the relationship between semi-quantitative score of musculoskeletal ultrasound, shear wave elastography (SWE) parameters and osteoarthritis index in patients with knee osteoarthritis. Methods A total of 90 patients with knee osteoarthritis admitted to the hospital were enrolled as the observation objects between July 2021 and July 2023. All underwent musculoskeletal ultrasound scan and quadriceps SWE to collect semi-quantitative score of musculoskeletal ultrasound and quadriceps shear wave velocity (SWV). The index of the Western Ontario and McMaster Universities (WOMAC OA) was evaluated. According to Kellgren-Lawrence grading, patients were divided into mild group (grade I-II) and severe group (grade III-IV), and all the above indexes in the two groups were compared. The correlation between semi-quantitative score of musculoskeletal ultrasound, quadriceps SWV and osteoarthritis index was analyzed. Results The semi-quantitative score of musculoskeletal ultrasound in mild group was lower than that in severe group (P<0.05), SWV of vastus lateralis muscle was slower than that in severe group (P<0.05), and WOMAC OA index was lower than that in severe group (P<0.05). Semi-quantitative score of musculoskeletal ultrasound and SWV of vastus lateralis muscle were positively correlated with WOMAC OA index (r=0.379, 0.435, P=0.000, 0.000). Conclusion The semi-quantitative score of musculoskeletal ultrasound and SWV of vastus lateralis muscle are positively correlated with WOMAC OA index, which could better reflect the severity of joint injury in patients with knee arthritis.