Thought I'd give my two cents on this thread.
Some years ago when I cut skinny trousers, I cut the leg closed. It has a similar effect as to what has been described in the previously posts.
Its the same pattern alteration as knock kneed. In the draft you swing the centre crease line over at the hem towards the crotch 3/4" to 1", depending
on how slim the fit is.
In my usual trouser draft 17" hem 18 1/2" knee, I open the legs. The reason being most men are bow legged. This cut is very comfortable for both walk and sitting and helps eliminate the unsightly creases when sitting. If wearer spent more time standing around I cut them straight on grain like when has straight legs. Experience has taught me its better to cut for the leg shape rather than usage particular when dealing with extremities.
Had a client with a 6 finger bow, walked like cowboy! In this instance I slashed above the knee and created a wedge, then minus the wedge from the side seam hem. This will work on most plain cloths not advisable on a check or strip.
Another tip that can be used on straight and bow legs (not Knock Kneed) is to drop the inside leg balance on the undersides. When picked up it creates a wedge of cloth at the buttock and eliminates unsightly creases at the seat. 1/2" usually does it.