What Causes Bruising On The Insides Of The Elbows?

I am developing bruising on the insides of my elbows. It started out as purple, now turning reddish brown/yellow. I did fall last week, but hardly seems that I would have bruised the inside of both elbows..and the right one started first...like 4 days ago and now I noticed last night the left one has started. I am 51 years old, obese, diabetic (oral meds), on 16 daily meds and just recently started walking 1 mile every other day for exercise. I am also on 3 different blood pressure meds.