For several years, my right knee / leg occasionally feels like giving way or buckling, most notably when I am in a squat position and stand up by pushing up with my right leg. There is no pain. Apparently unrelated to this my knee bones (especially the right knee) make a cracking noise when I walk up stairs but only if the stairs are very steep. I am a male aged 56.
In the past, visits to my doctor, a consultant and a physio therapist have not really helped although I have had an MRI and an arthroscopy (keyhole) knee surgery to flush out "debris" (minute bone wear). The noisey knee joint was put down to age and general wear and tear but no real diagnosis or recognition was/were ever given in respect of the "giving way" problem.
Reading various web sites suggets a possible ACL ligament problem but, as I have had this for 3 years or so, and there was no sudden causal / sports injury problem, it may not be this. I wonder if the ACL can gradually wear with age. Whilst I get no real pain, I can replicate some tenderness if I push the sde of my right leg along the line that I have indicated on the attached picture: ->
However, the tenderness is in a general area rather than one rea "ouch" point. Maybe the tender area is very deep.