Seen a Physio this morning..
He said its my hamstring that i have sprained. This is causing me not to straighten my leg fully when walking and standing which is causing the other muscles to overcompensate and pull. This in turn is causing my knee instability
He has given me stretching and strength building exercises to do and told me not to use a crutch to walk as it will make things worse.

I have to do the exercises for a month to see if it improves
Hopfully it will get better