Good afternoon to you Martin
Really great to hear from you .
I know that u requested folks that had upper body primaries to respond but I'm chiding in anyway
You had a bone scan back in February right ?
Have you been jogging more lately as well?
With the location of your surgeries I would guess that your knees sometimes get to feeling sore as the back is very much a part of the transference of weight to the knees.
Healing and trauma could make you favor weigh that you put on your knees and cause pain maybe ?
If you can get a scan ok'd , I would perform an MRI.
Have you followed up on your liver spots lately or how often are scans being scheduled ?
Our family had a beautiful holiday. Thanks for asking
Knee link-
How Can I Prevent Knee Pain?
Knee pain can be hard to prevent, because it's often caused by an accident. But there are still some precautions you can take to reduce the risk of a knee injury:
Stop exercising if you feel pain in your knee.
Always increase the intensity of your workout gradually.
Stretch your legs before and after physical activity.
Use kneepads to prevent bursitis, especially if you have to kneel frequently.
Wear shoes that fit well and offer enough support.
Keep your thigh muscles strong with regular stretching and strengthening.
http://www.m.webmd.com/pain-management/knee-pain-causes