Forward lunges are great for working the lower body and can be done with added weight or simply using the bodyweight. However, if done incorrectly they can cause many back, knee, and ankle issues.
To avoid injuries, always make sure to keep the hips square and step out far enough so that your knee does not pass the toes. Also, you will want to keep your shoulders stacked over the hips as much as possible and try to keep the spine parallel to the tibia.
See pictures for just a few common mistakes that are made when performing the FWD lunge:)