Occasional pain on the inside of the knee

About 3 to 4 years ago, I suddenly started feeling a stiff sensation in my knee.

Since then, I experience pain when squatting down and can't put strength into it (there's no swelling and it looks fine).

Since then

Sometimes, when I experience noticeable but not severe pain on the inside of my knee that bothers me, applying a magnetic patch would make it disappear within a few days.

However, recently I experienced pain severe enough to make walking uncomfortable, so I am worried and am inquiring.