Hello, so the main problem is that when I walk sometimes for no reason I start to feal pain in my right knee so I limb. Also when  I do one legged squats my left leg is fine my right one after 90degrees just falls like no muscle wouldnt work, if i stop about 90 degree its really hard to stand up.  But with the left leg everything is ok. When squating with both legs i dont feal any discomfort or pain at all. Both of my legs  muscles are same strenght. So what could it be? Sorry for my bad english.