Do you remember a few years ago when everyone and their mother was wearing the J Brand Houlihan Low-Rise Skinny Cargo Pant? Well in an attempt to curb my shopping diet, while still updating my wardrobe, I moved my skinny cargo pants from the giveaway pile, to the update it pile. I was inspired by these FP Patched Twill Herringbone Pant to transform my skinny cargo pants into Moto Pants with knee patches- making them the perfect Spring pant.
Gather your tools and supplies- Any skinny cargo pant or jean + painters tape (or masking tape) + sponge brush + water based black fabric paint. I used this kind. 
Tape off your knee patch shape. My pants had knee patches already, so I used the seams as a guide. If your pants don’t already have knee patches, then try them on first and use pins to mark your knee patch area and measure them to ensure they are symmetrical. 
Once you tape your knee shapes, apply paint very lightly, one layer at a time to the pants, allowing each layer to dry before applying another. Keeping the layers of paint thin allows for the seaming details to show. After everything dries, remove the tape and wear them! Check in tomorrow to see how I wear my new favorite pants.
I wish I bought some of those pants in 2009 because I love love love the update you made!
Great idea!