Sometimes I get pain in my knee and ankle, at 5 months why?

I’m over 5 months post my tibia nail operation. I’m pretty much off my crutches and have walked as much as 7 miles in one day.

However, obviously at a slow pace, and I do not walk properly at this stage.

At times after exercising, for example, leg presses or goblet squats, my knee hurts.

I’m just back from a short walk and again my knee hurts when standing, along with my ankle.

This pain only appears when I exercise.

Anyone know why or had experience with this?