comparative evaluation of core and knee extensor mechanism muscle activation patterns in a stair stepping task in healthy controls and patellofemoral pain patients.

background: patellofemoral pain (pfp) is a common affliction and complex clinical entity. deficit in neuromotor control of the core may be a remote contributing factor to the development of pfps. comparative evaluation of core and extensor mechanism muscle activation patterns between healthy group and patients involved by patellofemoral pain syndrome(pfps) in a stair stepping task is the aim of this study. methods : in this non-randomized interventional study fifteen males with pfps and fifteen asymptomatic controls participated. electromyographic(emg) activity of vastusmedialisobliquus(vmo),vastuslateralis(vl), gluteus medius (gmed),gluteus maximus (gmax),internal oblique (io) and erector spinae (es) were recorded and emg onsets were assessed in both stepping up (su) and  down (sd).the time of foot contact determined by a foot switch. results: during su:onset times of all muscles except, vl and es in the controls were significantly less than pfps group (p < 0.05). in pfps group the temporal sequence ofes, vl and vmo were different from control groups.during sd:onset times of all muscles except, gmax and es in the control group were significantly less than pfp group (p < 0.05). the sequence of muscle activity in both healthy and pfp groups were the same. conclusion: our findings are in line with previous researches about the effects of core on function and control of lower extremity. activation patterns of core and vasti muscles are different between control and pfps group during stair stepping task. designing exercises to correct inappropriate timing of core muscles may have a role in management of pfps and it needs more future researches.