Dad is leaning to one side

Hi, Firstly thank you so much for this forum. It really helps me as a child of a father suffering from PD. I feel I have a online support group. Especially those with PD that take the time to reply to the post.
My dad is 74. Was diagnosed a couple years ago. Aside from a resting tremor he was doing okay up until a year ago.
He suffers terribly from severe constipation which bothers him immensely. He takes all kind of laxatives prescribed by the Dr, He eats prunes and other alternatives but no relief. He also had installed in his bathroom a shower next to the toilet. Any other recommendations?
Recently he has also had terrible sciatica pain. lower back pain, and knee pain. and now he started leaning to one side? I’ve read online its called leaning Pisa. I’m trying to find him a physio to do home visits. He is still very busy at work and walks daily to his office, but his new pain and leaning to one side is really slowing him down. Any help?
Thanks in advance. I am so worried about him