After a little break in running I've started again, but now I'm getting pain just below the kneecap of one leg that gets worse when running and I can still feel days later in certain positions.
The muscle feels sore when I press on it, but it doesn't seem swollen.
Is this a common injury? What's the best way to strengthen that muscle, or should I just give running a break for a week?
A common condition that matches your description is patellar tendonitis. It certainly could be other ailments as well.
You can try taking a NSAID for a few days. I will typically take the maximum dosage of Aleve (naproxsen) for up to 4 days before reducing dosage over the next week at most. You don't want to stay on a NSAID for an extended period of time.
In addition to medication, you can ice the area after runs, or take a few days of complete rest.
In you current condition, the ailment should go away in a week or 2, especially with medication, rest and ice.
These types of injuries are typically from overuse and in the case of running - probably too much, too soon, too quick.
I've had issues with my knees since I tore them all up at 14 years old.
If it is an injury, you need to be super careful not to make it worse. When I push myself too hard, I'll have some stiffness and pain in the joint, and the soft area directly below the kneecap becomes inflamed and feels weird to the touch. Over time, with regular exercise without overdoing it, the symptoms eventually relax to where you can push a lot further without it bothering you.
Muscles can also just remain sore for several days, and if you aren't swelling or experiencing severe pain, it may be possible that it's just muscle soreness. If it bothers you pretty bad, take a little time off running and try something with less impact on your knees, like walking.
Also pay attention to the surfaces you run on - certain treadmills mess my knees up after about 5 minutes of running, pavement kills me after about 30. Dirt or an actual running track I can run on indefinitely without any pain or problems. You might see if changing the surface you run on has any effect on it.
First, a small point. Right below your knee is not a muscle, that is the patellar tendon.
I have a couple questions that might point out a few things. You say you haven't run in a while, and now you have been running a week. How long is a while? And in that week, how much did you run, and what kind of running was it?
What kind of surface do you run on? And probably the most important, what shoes did you run in? Did you just dig some out of the closet and go run? Or did you get dedicated running shoes?
