A thigh strain or quadriceps strain is a tear in one of the quadriceps muscles at the front of the thigh. It can range from a mild discomfort to a full blown tear of most of the muscle resulting in severe pain and inability to walk.
The breakage of the stitches starts within 2 weeks of the stitching but if you want the complete stitches to disappear then the process of hydrolysis or the enzymes in our body do that in a period of 60 days and therefore it approximately takes up to 2 months for the stitches to get dissolved.
I would maintain that stitches should stay in at least 5 days and no longer than 8 (wound separation can potentially occur if sutures are removed too soon). The type of skin suture used in my practice is a 5-0 or 6-0 prolene, which is a non-reactive mono filament suture.