Why does your knee swell with fluid and blood when it is injured?

Question

My 20 yr old daughter recently fell over a concrete step and bashed her knee. The hospital says that it is not broken but it has swollen to the size of a large orange and today has had to have a bloody coloured liquid drawn off of it.

Answer 1

Hello:
This answer is in response to your question posted on yahoo concerning knee injuries.
When you traumatize any joint, especially knees, a process known as inflammation occurs and is a normal part of the healing process. As inflammation occurs, fluid builds up in the joint, there is a capsule around the joint so the fluid stays inside and consists of serum, blood, white and red blood cells and other cells that are part of your immune system, all responsible in helping heal the traumatized area. When she hurt her knee, she probably broke some blood vessels in and around the joint. The bones that make up the joint have a considerable blood supply to nourish the bones so if there is a blood vessel that is compromized, the joint will fill with blood. Along with the blood and the other fluids in the joint cause the swelling and to ease the pain from the increasing pressure caused by the fluid, it is usually drawn off using a large bore needle. Some of that fluid will return, but eventually, as the body heals the area, it will go back to normal size. Wrapping the knee with an ace bandage is probably a good idea and trying to keep off the leg as much as possible also is a good idea. Do not use heat on the area as this will increase the inflammation and also could cause more bleeding. Use an ice pack. I tell my patients that a bag of frozen peas is the best ice pack because it conforms to the shape of the knee and you can refreeze it afterwards and use it over and over. Then you can serve the peas later for dinner! (haha).
I hope this helped to answer your question and alleviate some of you concerns.
Regards,
Warren Shaffer, M.D.

Answer 2

Very good question.

Swelling is the body's way of telling you that you shouldn't be using that part of your body. This occurs when you sprain an ankle for example.

When swelling occurs, the body keeps pumping in fluids to protect the injury. The body only stops the swelling when the force of the liquid inside the injury is sufficent to stop the flow.

When you injure a joint, the swelling is more severe because of a couple reasons:

A) The joint experiences more motion. Swelling increases as a result, becuase you're damaging more tissues.

B) There is extra room around joints. Because there are only tendons (no real muscle structure to impede the joint), more fluid can exist around the area.

These are the two most common reasons for excessive joint swelling. There are others, however, these are the leading reasons.

Answer 3

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Answer 4

Well, the bloody liquid is from broken blood vessels...eventually it should cause a big bruise. The clear-ish fluid is what is called cynovial (not too sure of the spelling!) fluid. It is always inbetween your joints; it's what keeps them lubricated and working smoothly. In a time of injury, the fluid builds up around the joint and usually has to be drained.

Answer 5

the knee is very vascular, and the knee joint has got a large potential space that can fill with lotsa blood and fluid (blood is very irritating to the synovial membrane and it secretes serous fluids in response), so it can get quite gross

don't worry, if it's just a minor injury, all the blood and fluid will be reabsorbed and all will be fine

Answer 6

The swelling which appears on the scalp after an injury is caused by damaged veins leaking fluid and blood into the skin.

Answer 7

The body produces water at the point of a swollen joint. Arthritics get fluid on the knees or joint from their disease. Ibuprofen will accomplish the same thing. It reduces swelling and inflammation. Much less painful than a needle.

Answer 8

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Answer 9

hey that happened to me..and the doctor i went to said nothing was broken...but that's because i didnt go to the right doctor....then when i finally did...i had a torn acl and torn meniscus...im not too sure about the fluid part...although it has something to do with white blood cells fighting off infections..well im not too sure...but she should go to the doctor again...and get an MRI...be careful with that knee...and dont but too much pressure on it....0h and ice it a lot...that helps the swelling.

Answer 10

Blood In Knee Joint