My legs (mostly around my knees ) have been feeling weak lately. especially when i try to climb stairs my cervical spine hurts as well. possibilities?

Multiple: Multiple possibilities, and undergoing a good medical checkup is probably a good place to start. Some possibile causes include deconditioning, peripheral arterial disease, a neurological condition such as a motor neuropathy. With your neck pain, there is a condition called myelopathy in which spinal cord compression in the neck can cause weakness in the legs as well. Don't hesitate to be seen.