Joint problems can be a real pain. 
To find out what's causing the problem, relieve the pain or help with treatment, your doctor may use joint&nbsp;aspiration&nbsp;or&nbsp;injection. Both require placing a needle directly into the joint.
An aspiration removes fluid from the joint space. An injection delivers medicine directly to the joint. 
When it's used
Joint aspiration may be used to help diagnose or treat a joint problem. To help with diagnosis, a small amount of fluid may be drawn out of the joint and sent to a laboratory. The lab can run tests to look for signs of specific diseases.
As a treatment, aspiration may be used to draw out fluid that has built up in a joint. This can relieve pain and make it easier to move, according to the <a href="[BASEDOMAIN]/healthinfo/bouncelink.aspx?shortcut=acr" target="_blank">American College of Rheumatology</a> (ACR).
Joint injections are used to put medicines in joints. A doctor may inject pain relievers, corticosteroids to reduce inflammation or a lubricating fluid that helps relieve pain from osteoarthritis.
Injections are commonly used in knees, shoulders, ankles, elbows, wrists, hands and feet. They can also be used in the hips and lower back. 
Joint injections and aspirations can be done in a doctor's office or hospital.
Risks
The most common side effect of an injection or aspiration is an allergic reaction. People may have reactions to the medicine put into a joint, the cleanser used on the skin or the tape used for the bandage. 
Unusual complications of aspirations and injections include whitening of the skin around the injection site, thinning of the skin or damage to soft tissue in the joint.
Very rarely, these procedures cause infection in the joint. They can also cause "post-injection flare," swelling and pain that start a few hours after an injection. 
As a rule, repeated and numerous injections into a single joint should be avoided, according to the ACR. 
Recovery 
Before the procedure, your doctor will probably give you a local anesthetic. After it wears off, you may feel some pain. You can use ice packs or ask your doctor about taking an oral pain reliever. 
According to the <a href="[BASEDOMAIN]/healthinfo/bouncelink.aspx?shortcut=aafp" target="_blank">American Academy of Family Physicians</a>, you should call your doctor if you experience redness, fever, warmth at the injection site,&nbsp;continued pain or an abnormal reaction.
Reviewed 6/20/2023

A guide to joint aspiration and injection 

These procedures are used to draw fluids out of joints or inject medicines into them.