What Causes Weakness In Lower Body While Suffering From Dislocated Shoulder?

Please help!!!!!! My dad is 83. He fell a year ago and dislocated his shoulder, he refused to do therapy after he was released. But he has progressively been getting worse. His hand started to shake, he said that he saw smoke around his waist, soon after that he began getting weaker and weaker. his biggest complaint is that he has absolutely no more strength in his lower body. His mind and his whole body is extremely weak!! We had him tested for alzheimers and dementia but all results came back negative. He won t even run a vacuum cleaner for my mother because he just can t. My mother is at wits end, should we take him to emergency?? Also, we had his back checked and he does have a bulging disc and some arthritis but not really significant. What do you think he could have??? HELP!!!!!