and thank you for your answer
as you explained me i have fat pad (Hoffa's syndrome) because i hurt below the patellar tendon not in the medial to patella.
as i said i went to two doctors,the first one is Sports Med doc and the second one is Orthopedic.
only the second one told me that i had Fat pad syndrome and suggested me rest-ice and Arcoxia anti inflammatory tablets.
i forgot to inform that i have both my knees ACL reconstructed(1995 left-2001 right) but without any problems all these years.
the pain started one day after leg presses early August and consists until today.it's not strong pain but it likes dull and is always there except in the night when i sleep.
i can walk,ride etc but always with this hurt.
when i did leg press my knees was straight,the knee angle was until 90° and the weight was 15kg.i think that it's not too heavy weight for press.it was the first time in my life that i did leg press.in the gym always i did leg extensions-leg curl-adductions/abductions,calf raises with low weights-high reps.warm up 10min to the stationary bike,stretching,weights and finally again stretching.
both saddle/pedal cleats setup is ok because i have done pro bike-fitting.
PS look at this photo the red circle to see where i hurt,below the patellar tendon.http://img201.imageshack.us/img201/3273/fatpad.jpg