I had a small bike accident this weekend and smacked my knee (just below the joint) and pulled or strained my thumb/pad of my hand.
Both areas swelled up, and I’m wondering what exactly is happening. What causes the injured area to swell? It certainly inhibits motion which is probably a useful side-effect, but that’s not the ‘purpose’ of swelling, is it?
Tissue damage releases fluid into the surrounding tissue. The medical term is edema.
I don’t think there’s any purpose to it. On the contrary, if you use an ice pack immediately after straining or bumping yourself, it’ll hurt less and - at least appear to - heal faster. Applying pressure and elevating the strained limb are also good. The first aid acronym is ICE (Ice, Compression, Elevation). Cooling can help up to 48 hours after the injury (or at least, that was the guidelines a couple of decades ago)
Tissue damage does release fluid, but it also releases histamine, a chemical messenger that attracts more fluid to the site. The fluid brings white blood cells to destroy any bacteria that might be present, and platelets, to stop up a bleed, and nutrients which cells might need for growth and cell division to repair the tissue. The fluid also takes away wastes from the cells and any toxins bacteria have left behind.
It also, as you noted, acts as a stabilizer, like a natural splint, preventing you from moving the joint too much.
This is all cool stuff, but our bodies tend to go overboard. Taking action to reduce the swelling (RICE, as mentioned - Rest, Ice, Compression, Elevation) is a good thing, and will make you more comfortable. I don’t know of any evidence that it actually speeds healing, but it will make you *feel *better faster. Just don’t forget the “Rest” part. Exercise (physical therapy) to keep things flexible and strong is good, but you need to balance it with resting the injury to allow cell regeneration to take place.
The application of ice, compression, and elevation does not speed healing. In fact, it retards the blood circulation to the area, which is what you want to prevent or limit the swelling. After 1 or 2 days, the cold compresses (ice, a bag of frozen peas, etc.) should cease and then you should apply heat to promote the circulation and promote healing. But the fact that there will be less swelling might speed up the healing processes.