If a child has jra and its in her knees can this cause her knees to give out sometimes? is there anything i can do to prevent this?

Exercise: Often knees give out due to pain. If you treat the pain and strengthen the surrounding muscles it lowers the chance of the knees giving out . Make sure she is evaluated by a doctor to determine that there is no structural reason her knees are giving out like weakness from nerve or ligament damage.

Yes, but....: Yes, but more likely due to quadriceps muscle weakness. Should respond to strengthening that muscle group.