How to strengthen knees?

Hey ladies,

My knees are very week! When i was 16 I dislocated my right knee and took me ages to recover! I never went physio or anything like that my doctor told me it wasn’t necessary at the time. He also informed me that my knee joints are very slippery and so doing any sports like ice-skating, surfing etc will cause the knees to dislocate easier.

Anyways my knees always crack ! When I’m walking up stairs, stretching or trying to do squats. I can’t squat low at all I can’t do lunges either

Are there any ways to strengthen the knees or to stop them from cracking ?? 😖😖