If you are looking to build a specific muscle, isolation exercises are key.
Isolation means the only joint that is moving is the one the muscle attaches or
Any bodybuilder would tell you leg extensions. You can also rotate your feet
externally to concentrate on that part.
This does not mean they should be your only exercise. The classic weight
training and bodybuilding technique of performing the multi-joint exercises
first, followed with isolation exercises has always been the best way to
hypertrophy your muscles.
The best exercises to completely work your legs involve full range of motion for
exercises such as lunges and squats, especially front squats which offer more
range of motion.
A quick leg workout would be performing say 3 sets of 8-15 front squats, with 3
sets of 8-16 walking or push-back lunges, followed by 3 sets of 10-15 leg
Remember when you perform leg extensions to always keep your toes (dorsiflexed)
pointing upwards to keep your patella safe. Perform slow and controlled motions
to keep your training volume high and as always eat a hyper caloric diet meaning
you are eating more than you burn.