2/3

Joint locks seem singularly focused. Armbars go after the elbow and ankle locks the ankle. However, success in joint locks depends more on control of the other two major joints in the limb under attack than the joint in danger. Arms and legs have three major joints and the principles you use to attack one generally apply to the other. So if you think of them both as a top, middle, and bottom joint extending from the torso, the possibilities of attack broaden quite a bit.
A quick guide of two thirds control:
Elbow- top joint/ bottom joint
Shoulder- middle joint/ bottom joint
Wrist- top joint/ middle joint 
Knee- top joint/ bottom joint
Hip- middle joint/ bottom joint
Ankle- top joint/ middle joint