Dr. House went on an eight week recovery . . . the longest one can take for having been shot in the neck and abdomen and being medically induced into a coma. However, it was mentioned he was supposed to have come back after only six weeks . . .
According to Dr. Cameron, they never found the shooter who attempted to kill Dr. House.
Secondary Addison's Disease
At some point, presumably during his earlier brain surgery, the patient here suffered damage to his pituitary gland or surrounding structures. Among other responsibilities, the pituitary gland produces adrenocorticotrophic hormone, or ACTH. As the name implies, this hormone stimulates receptors in the adrenal cortex (outer layer), causing cells there to produce cortisol. Cortisol is essential in the stress response and in many other normal metabolic functions, especially sugar level control. Insufficent cortisol produces a rather long list of symptoms including muscle weakness and gradually worsening fatigue. It is likely that in this case surgeons assumed the cause of symptoms was damage to the motor cortex, motor thalamus, or other structures of movement, and therefore did not look for Addison's disease.
The song You Can't Always Get What You Want also played in the first episode of the first season, the pilot.
The scene where Wilson claiming that House's leg hurts because of running is similar to House's quip back in Occam's Razor: "Her leg hurts after running six miles. I don't know, it could be anything!"