It depends on the filler material. If you have a saline filled implant your will notice a asymmetry. Similar to a flat tire.
If you have a silicone filled breast implant rupture it may be a “silent rupture” and be totally asymptomatic. This is most recently found with the new “gummy bear” type implants. It’s recommended that you undergo a MRI (non radiation) study 3 years after breast augmentation and the every two years. Ruptured and leaking silicone can cause a reaction caused capsular contracture resulting in a more firm or hard feeling of the breast,
Distortion of the breast shape or even pain.