Edema and effusion both describe swelling, but the key difference lies in the location of the fluid accumulation.
| Feature | Edema | Effusion |
|---|---|---|
| Location | Tissue outside of a joint. | Inside a joint. |
| Description | Swelling in the interstitial tissue. | Swelling within a joint cavity. |
| Examples | Swollen ankles due to prolonged standing. | Swollen knee after a sports injury. |
As stated in the provided reference, edema describes swelling in the tissue outside of the joint, while effusion describes swelling that is inside a joint, such as a swollen ankle or knee. Essentially, if the swelling is contained within a joint capsule (like the knee or ankle joint), it's called an effusion. If it's swelling in the surrounding tissues outside the joint, it's called edema.
