No obvious cause. Started 24 hours ago and got worse. By last night, I could hardly move my leg - severe shouting pains when I tried to lift my leg. Sort of behind the knee. Definitely, when I moved a certain way.
Today its 75% better I'd say - at least I can walk. Still a bit of dull ache but hugely better - no more shooting pain.
What could it be? Trapped nerve possibly?
I do wonder if I slept with my leg in a strange position the night before and somehow inflamed things. (Fell asleep on sofa until 4am!) with my legs up on recliner.
I have got the same sort of thing , if i have been sat down or in bed then get up it feels like my tendons have shortened and i get shooting pains in the back of my knee and down my calf!! Once i have stretched and started moving the pain goes away but the initial get up and walk is really painful, dont know what it is.
Glad it's better; Could be from sleeping in recliner. I had a procedure done at Flexogenix's in Greensboro, NC. It was called a Nerve Dissection Treatment. And it did just that. Can get one every 3 months. It really helped me with the nerve pain.
For sudden onset knee pain, there is ALWAYS a cause...you just have to relive the previous 24 hours to remember it. Anything with the knee requires ice and elevation. Stay off of it for a few days. Some NSAID anti-inflammatory would be appropriate for up to a week. If it's not better, no GP...see an orthopedic surgeon. An x-ray plus the exam could isolate the problem. When the doc pulls, pushes, bends, twists and turns the knee, they will know exactly what's going on...after they peel you off the ceiling.
Right now, I'd just play it safe and treat it as a sprain. You will know within 10 days if you need a real diagnosis.