I have a 2015 Felt Z85 with Shimano 105-5800 groupset. I am 5'8.5" (174cm) tall. The bike has a 50/34 FC-5800 crank with 172.5mm crank arms and SM-BBR60 threaded BB

I have pain in the front of my knees just inside the kneecap, not underneath the kneecap, to the side of the kneecap on the inside of the leg. It doesn't hurt while riding, but it hurts afterwards when bending at the knee, like doing a deep knee bend.

I've been doing some research and have found that this can be caused by crank arms that are too long. I have raised my seat to the point of causing hip rocking and the knee pain still exists. I have decided to try a 165mm crank, I think 170mm is unlikely to provide enough of a difference and 167.5mm cranks don't exist (practically speaking).

My questions are

The FC-5800 is not current and difficult to find online, especially in 50/34-165mm
1. Can I substitute an FC-R7000 or FC-R8000 crank in this configuration? From the Shimano compatibility chart (pictured below), it seems yes Unless my Front Derailleur is FD-9070 or FD-6870. I don't know what Front Derailleur is on the bike, but it is a model that clamps onto the seat tube.
2. Regardless of FC-5800, FC-R7000 or FC-R8000 replacement, if I find a 165mm crank version but it has standard chainrings 53/39 or 52/36, can I swap the chainrings from my current FC-5800 to the new crank?


Here is a picture of my crank



Here is a poor picture of my BB

In thinking about the Shimano chart, I think my Front Derailleur (FD-5800 I believe) is incompatible with the FC-R7000 since those two boxes are not connected on the chart.

I have ordered an FC-R7000 and an FD-R7000 (since the FC-5800 [MENTION=381353]165[/MENTION]mm is non-existent). That should take care of it.