Why are my middle finger joints swollen?

Swollen middle finger joints can be attributed to a condition known as trigger finger, which is a type of tendonitis that has developed in the tendons that allow the fingers to bend according to Eaton Hand, the electronic textbook of hand surgery. Tendonitis is a result of the body's own tendency to collect fluids around the tendons and joints and may be caused and aggravated by repetitive or strenuous activities.

When the tendon swells up, it interferes with the normal movement of the tendons, causing the joints to lock up. To treat this issue, patients can implement the "RICE" method, which involves resting, icing, compressing and elevating the affected finger.