The trembling of the cat's hind legs after stepping on milk may be caused by long-term calcium deficiency or estrus. You need to observe whether the cat has other abnormalities. If the cat usually also has trembling hind legs, lethargy, and inactivity, etc. The situation may be caused by calcium deficiency, and the cat needs to be supplemented with calcium in time; if the cat usually has no other abnormal symptoms, then it is in estrus, so don’t worry too much.