Updated: May 13, 2021
Our quadriceps comprises of 4 muscles.
All 4 muscles work together when we walk or run.
But when one muscle is stronger and one is weaker, it will pull the patella towards the stronger side which will cause pain. This is called the patellae tracking disorder, also known as runner's knee.
There are a number of reasons why one quadriceps muscle gets weaker, which has to be diagnosed by a physicians.
One of the reasons why your quadriceps might weaken is the increase in the knee valgus angle. The muscle on the inner side of the thigh will weaken as valgus angle is increased because it's stretched. Stretched muscles weaken over time.
One other reason is that the foot is in hyper-pronation. Hyper-pronation is pretty much the same thing as flat foot. When the foot is flat, it will turn other tibia(shin bone). If the tibia is rotated, it will cause knee valgus, and will eventually weaken the quadriceps on one side.
In conclusion, we need to know the cause behind the reason why the quadriceps become weak, in order to fix runner's knee. These are not easy to self-diagnose, so it is recommended that people seek help from a physician for their knee problems.