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A measurement method of knee joint space width by ultrasound: a large multicenter study.

Background
Although plain radiology is the primary method for assessing joint space width (JSW), it has poor sensitivity to change over time in regards to determining longitudinal progression. We, therefore, developed a new ultrasound (US) measurement method of knee JSW and aimed to provide a monitoring method for the change of JSW in the future.


Methods
A multicenter study was promoted by the Professional Committee of Musculoskeletal Ultrasound, the Ultrasound Society, and the Chinese Medical Doctor Association. US study of knee specimens determined the landmarks for ultrasonic measurement of knee JSW. The US of 1,272 participants from 27 centers was performed to discuss the feasibility and possible influencing factors of knee JSW. The landmarks for US measurement of knee JS, the inflection point of medial femoral epicondyle and the proximal end of the tibia, were determined.


Results
The mean knee JSW1 (medial knee JSW) was 8.57±1.95 mm in females and 9.52±2.31 mm in males. The mean knee JSW2 (the near medial knee JSW) was 9.07±2.24 mm in females and 10.17±2.35 mm in males. The JSW values of males were significantly higher than those of females, with a statistical difference. JSW values were negatively correlated with age and body mass index (BMI) to different degrees and positively correlated with height.


Conclusions
The novel US measurement method can be used to measure knee JSW.