when do you know you need balljoints, i replaced the struts and my car and it still hits hard when i go over a bump in the road and also whats cause it to shake very badly around 60 mph. i have the tires and wheels checked and they say the tires and wheels are in good shape what can this be?

ball joints, tie rod ends, or sway bar end links would be my guess.

just cause ur rims and tires r in good condition doesnt mean they r balanced