Sensations caused by emotional or physical states

подгибаться/подогнуться: у Ng ногиn подгибаются;
подкашиваться/подкоситься: у Ng ногиn подкашиваются
N's legs give out
NB The above expressions are used to describe a symptom of fear, fatigue, weakness, etc., but not drunkenness.
ноги как ватные;
не держать [no Pf.]: Na ногиn не держат;
слушаться [no Pf.]: Na ногиn не слушаются;
у Ng ногиn не действуют
N's legs turn to rubber (lit. вата "cotton wool")
NB The above expressions are used to describe a symptom of fear, fatigue, weakness, etc., and also drunkenness.
держаться [no Pf.]: Nn едва держится на ногахp N's legs can barely support him
NB The above expression describes a symptom of fatigue or weakness, and also drunkenness.
таскать [no Pf.]: Nn еле таскает ногиa N can barely even drag his feet
прирасти [no Impf.]: у Ng ногиn приросли к землеd N's feet are rooted to the spot
NB The above expression describes a symptom of fear, horror, or emotional shock.
дрожать/задрожать [Pf-begin]: ногиn дрожат;
трястись/затрястись [Pf-begin]: ногиn трясутся
someone's legs shake; someone's knees knock
NB The above expressions describe a symptom of agitation, fear, or fatigue.
заплетаться [no Pf.]: у Ng ногиn заплетаются N trips over his own feet, stumbles at every step
NB The above expression is used to describe a symptom of weakness, fatigue, or drunkenness.
не чувствовать [no Pf.] под собойi ногg to not feel one's legs
NB The above expression is used to describe a symptom of fatigue after walking a long distance or standing for a long time. Note that a similar expression, не чуять под собой ног is used only idiomatically to refer to a state of elation, excitement, happiness, and is said of a person who, being in this state, is walking fast or running.