If you're 78 and your knees were fine until you got Covid, I'm suspicious that it's arthritis. I'm 66 and have had osteoarthritis for 30 years. It's almost always a slowly progressing disease. When I was first diagnosed, I had no symptoms and they've gradually manifested and worsened over the years.

I'd ask your doc if it's tendinitis or another temporary condition resulting from Covid.

As far as gabapentin goes, I've never taken it and, even though I've got severe arthritis in most joints now, never been prescribed anything other than NSAIDs for inflammation/pain relief.

Try to make the effort to get mild exercise to strengthen your thighs and the muscles around your knees. Always look at drugs as a last resort. Almost all have undesirable side effects. Hope this helps!