Hello, I just noticed an unusual weakness in my right knee yesterday. I squatted down to pick something up from the floor and my knee gave out with an unusual feeling. It wasn t so much pain, but an sting. I couldn t say whether it was a tingle or quick shock, but it happened again today, twice. There is no issue when walking or sitting and getting up from a chair. I try to squat and I start to feel some weakness. With the point of weakness, I feel like it s potentially causing some feeling in the hip and thigh. I decided to stretch it out a bit while sitting on the floor, with no really pain or restriction. However, I did try to loosen and stretch my hip by leaning my hands against the wall and swinging my leg, in a semi-controlled fashion, in front of my body, swinging it left, and then back right. I notice in this instance that I feel a slight sting across most of the leg near full extension and twist. I tried it again this evening and I had a sharp sudden feeling that I couldn t quite pin point, but it made me fall to the ground - I was able to control myself with the fall. The fall feels like more of an involuntary reaction by my body to react to the pain. Again, it s less like pain to me and more of a sharp sudden sting. I don t recall any traumatic injury to it. In fact, it s quite shocking. The only real work out I had was a one hour spin class two days prior. I do spin on occasion. I m not obese (6 6 223 lbs). I m 35 and have flat feet and wear a high quality orthotic insert in most shoes, and used structured sneakers with special support as well. I even wear orthotic sandles around the house for the past 9 months. I ve always had flat feet that have caused on and off discomfort of the years but really started to be more regular mid last year. I m curious if you have any initial thoughts and what type of doctor would you recommend I speak with. I don t need to see my family doctor with my plan and can go directly to a specialist. If this sounds familiar, what do you imagine it could be and how could I treat it. The instability when squatting makes me think about ligament tears but I don t recall any sudden actions or trauma that resulted in any immediate pain in recent weeks. Thank you for your time, Mike