Q.My 5 year old philo has black knots on the stems
My 5 year old philodendron has black knots on the stems. Is this a disease? The plant has begun losing a lot of leaves.

Mine too! And its killing them all! Its some kind of virus or bacteria I am sure of it! Has yours progressed? Hopefully yours is just the lack of light or something simple like that

The dark knots on the stems where leaves branch off of our normal.
Is your plant getting enough light? If the plant is getting leggy, it is needing more sunlight.
Let your soil dry slightly between watering. Philodendrons respond pretty quickly to corrections in care.
Here is an article that has good information.
https://www.gardeningknowhow.com/houseplants/philodendron/caring-for-philodendrons.htm