DISCLOUSURE: I AM NOT A DOCTOR.
Trekking Pole,,,,hey? Well, if you do not mind, I will get back to that later. I will share some thoughts based on your comments:
You will get aches and pains as you get older. I got 'em.
Exercise: :rollH: I believe excercise is a lifestyle and as such if a person enjoys hiking/backpacking a person should keep fit and excercise at least three times a week.
Not stretching properly:
I am quilty of not doing this prior to a hike.
Sciatic nerve/lower back pain: :pois: I know the feeling of lower back pain and knee pain, up close and personnal. Abused myself when I was a young man and haven't seen a doctor, so I am sure I will pay for it later in age. However, I do not carry my wallet in my back pocket, haven't done it in ten years, and I do exercise to keep the middle down (I am getting old) so it does not put any undue pressure on my lower back.
Have not seen the doctor: :A2: GO SEE HIM OR HER.
I got my first walking stick when I was 35 and was planning to go in the Grand Canyon for the first time backpacking. The reason for purchasing it was to use it to help steady myself with backpack going down to the river. Later I did purchased a trekking pole, but I rather use my walking stick. I have to say it is my best piece of equipment/companion and I have commented on the many uses on other posts. However, I did not buy it to help relieve knee pain/lower back pain while hiking and I believe it is the wrong purpose to aquire one for that reason. Although, admittingly, I have used my stick after hurting myself while hiking and backpacking.
In closing, if you are experiencing knee pain/ lower back pain recently on some hikes I would suggest seeing a doctor and see what you can do.