Once working your legs in a single plane becomes easy, you can work them in different planes of movement with PNF exercises. PNF stands for Proprioceptive Neuromuscular Facilitation. I am going to show you PNF exercises for lower extremities in standing so they not only challenge your movements, but they also challenge your balance.
The first pattern is the D1 pattern. It looks almost like a figure 4 to start with. You want to start with hip flexion, hip abduction, hip external rotation, dorsiflexion, and inversion of the foot. Then take the movement down and out into hip extension, hip internal rotation, plantarflexion, and eversion.
The next pattern is the D2 pattern. It looks like a dog peeing! With your leg away from you, start with hip flexion, hip abduction, hip internal rotation, dorsiflexion, and eversion. Then pull your leg in and behind you to hip extension, hip adduction, hip external rotation, plantarflexion, and inversion.
Try to make it as smooth as possible, and try to keep your balance!