Knees are complicated and vulnerable to injury because they have so many different structures running around and through them. They are meant to bend only one way and rotate a little, but that's it. Knees aren't made to move much. They also take incredible amounts of pounding when you run.
The many different knee injuries have varying symptoms, but many of them are felt around the kneecap. If you're feeling pain at the bottom of your knee when you run, rule out a few major problems. The first thing that you should do if you feel pain in that area
A relatively chronic condition that could cause pain at the bottom of your knee is Jumper's
The name of the injury comes from the way it usually occurs, which is from high impact forces like jumping. Repetitive motions like running can also cause patellar tendonitis. You might not feel pain while walking around during the day but it usually gets worse as you run and the tendon becomes inflamed. You can help by gently stretching and strengthening the tendon.
Unlike Jumper's Knee, the cause of Runner's Knee is not very clear. It's more proper name is patellofemoral pain syndrome or PFPS. It's one the of the most common injuries seen by orthopedists in an outpatient clinic and 20 to 45 percent of adolescents will experience it, according to an article from Columbia University.
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The cause could be improper footwear, too much exercise or a kneecap that moves out of place. It might not hurt while you walk but your knee will probably hurt when you descend stairs or run. Pain is usually felt right where the kneecap meets the leg bones. Rest, ice, anti-inflammatory drugs and light strengthening exercises usually help take care of the problem.
The pes anserine bursa is a small sack that fits right under the pes anserine, which is the tendon that connects your hamstrings and adductor muscles to your shin bone. It runs across the inside of your knee. If you run too much without stretching you can irritate the pes anserine bursa because the tendon rubs over it too much, which will cause swelling
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The patellar tendon connects right below your knee to your shin. The spot where it connects is soft as you grow up and the patellar tendon pulls on that soft spot in the bone. It creates a bump right below your knee on your shin that you can reach down and feel.
Most children don't need any special procedure to get rid of their Osgood-Schlatters since it usually stops as long as the growth spurt finishes. However, if the bump grows too big, surgery might be performed since the bump will never get smaller.