He sleeps during the day in the upstairs closet or on the bed. Same for during the night. Jumped on the bed at 0630 this morning and howled. Our rooster cat. Petted him and he calmed down. Usually howls at night and in the morning when I carry him downstairs for feeding or to use his litter box. Once he's finished, he shoots back upstairs with a slight limp on the right rear leg. Will have to get him back to the vet for the other tests that you suggested. Thanks.