My client is a fitness instructor and of course squats tend to increase the size of your thighs. So his trousers fitted perfectly everywhere else except the thighs. The trousers were also too long, so I used the fabric from the length to insert a gusset at the crotch and thigh area.
My suggestion to him is to purchase trousers that fit the thigh and I will alter the trousers to fit the waist and hip area.