I just started pain right below the left knee cap

Take a couple days off and see if it works itself out.

Ice and a couple of Advil with dinner. Sounds like Patellar Tendonitis. No hopping, skipping, bounding? No weights with legs? Excessive downhills?

If pain is gone tomorrow, try to stretch the quad by laying on your stomach. Drive that knee into the+ floor for 5 seconds. Straighten the leg. then Bring heel directly to butt and lift knee off the floor. Hold for 20 secs.

No jumping, weights or bounding. It just started an hour ago. There is no swelling at least not yet. I will take advice from both you and rest.

I did lightly sprain my ankle on the other leg 3 days ago. Took a cautionary day off and went to run yesterday. I wonder if I was unknowingly compensating with the left leg. My ankle was fine during the run but I was slightly trying to be careful.

i've had something like that that i dubbed "weird knee thing" (it's a technical term).

i couldn't run or bike with it. i went to PT and the theory is that something caused the patella to go off track and it caused irritation. once it's irritated, it takes some time to go away.

i wonder if the ankle sprain could have done this.

the suggestion was to do the straight legged leg lifts with ankle weights. it seemed to work.

The pain got worst yesterday afternoon. It had like sharp stinging or electricity like feel to it. Touching right below the knee cap area with my fingers, I can feel stinging pain. Then in the evening as I was talking on the phone, I feel something happening in that area. I thought I was imagining things but somehow pain disappeared by late evening. No pain all day today. I am still going to take at least 2 more days off to be safe.

What the hell was this? I think I may have figured out when I hurt it even though the onset of pain happened almost a day later. There was a part of a trail where the surface was up higher than the rest. I landed with a shock on the higher surface area and may have jammed things in my leg including the knee area.

Something like this happened to anyone else? And why was the pain coming and going like clockwork every 15 to 25 seconds?

Yes. How did you get to your 40s without experiencing anything like this?

It's totally normal to have random sudden twinges that come and go over the course of a day or so if you do anything physical.

Often people who have been active as kids have some pretty mangled tissue on the outside of their knees and one of those loose fragments moving around a fraction can feel like a nail driven through the knee.

I guess I've been lucky so far. Should I expect more of this in the future? I've been injury free most of my running career dating back to college. I was really going nuts because nearly all of my male friends have had at least one knee surgery. And none of them run. I thought here comes my turn.

So the pain coming and going probably means now I probably have loose fragments there swimming around. What a bummer.

Freaking out wrote:

I was about to get dressed to go run. The pain is not at the knee but right below the cap. The area that meets the lower leg bone. I thought maybe I sprained something but now it is ongoing for 40 minutes. The pain comes and goes every 25 seconds. I never had a knee problem before but this does not feel like something I can run though. Is this Patellar tendinitis? Some kind of tear? Yesterday's run was fine. Mid 40s age.

Try just taking a few mins to examine the "hurt" knee from the other one. Is there any visual swelling or color difference? Can you palpate around the knee and physically feel for inflammation? I would try just mobilizing your patella a bit on the health side. Sit so your back is supported and your legs are straight out in front of you. Move the patella around on the good knee..get an idea of how it feels going up and down and side to side. Your quad needs to be relaxed when you do this otherwise it will be hard to mobilize.

Now try it on the other knee...if you have any type of irritation/inflammation and it's causing your patella to track funny you should notice some type of restriction or difficulty to move it around. It also might help you pinpoint the source of irritation. I'd do this a few times a day with ice. As long as you aren't having trouble completely straightening your knee, or feeling a catching/clicking sensation, or feeling as if it's going to buckle when you go up/down the stairs, chances are it's something that will heal on it's own. Don't freak out.

Thank you all for advice. For now, I think I averted a disaster. I seemed to be ok. I took today off as well. I will try easy 4 to 5 miles tomorrow.