How to train legs with a hyper flexed knee

So basically when I try to squat I feel a sharp pain in my knee. After that I’ve found it hurts to put pressure on that leg when walking. I still wanna train legs though.

So is there any way to train legs around this. Are there exercises similar to squatting that give the same strength gains that don’t put pressure on the knee?

(Gyms are not open where I am so I’m train from home, therefore have no access to machines)