Ultrasound investigation of vastus medialis oblique muscle architecture: an in vivo study.

There is thought to be a link between vastus medialis oblique (VMO) architecture and patellofemoral pain syndrome (PFPS). Historical data are largely derived from older populations, whereas PFPS commonly affects younger populations. The aim of this study was to gather data on VMO architecture in young asymptomatic adults, to provide baseline values for comparison with symptomatic sufferers. VMO maximum fiber angle and insertion ratio were measured with ultrasound. The insertion ratio represents the proportion (%) of the patella which has the muscle fibers attaching to its medial border. Eighty knees from 40 healthy young subjects (18 males, 22 females, and age 20-30) were assessed. Individual Tegner scores were recorded to assess participants' level of physical activity. Results were compared with data in the literature for PFPS sufferers and normal older individuals. Mean fiber angle and insertion ratio were 56.6° and 57.8%, respectively. There was no significant difference between age groups. The insertion ratio was higher among females (61.2% F:53.6% M). There was some evidence of increased fiber angle and decreased insertion ratio with increased Tegner score. There was some overlap in fiber angle between healthy knees in this study and values reported elsewhere for pathological knees. VMO fiber angle and insertion ratio are not age-related. The overlap in fiber angle values between healthy and pathological knees suggests that the cause of PFPS is multifactorial. An individual's VMO architecture may be affected by their physical activity level, which could have important implications for PFPS.