What would cause a gland to be abnormally swollen?

Swollen gland: Likely what you are describing is something called lymphadenopathy, which is swelling and inflammation of lymph nodes. This can lead to pain and can be aggravated by movement, depending on the location of the swollen lymph node. Generally speaking, most lymphadenopathy is caused by infectious processes. This could be viral or bacterial. Other causes can be chronic disease or malignancy.

Lymph node: If it is acute and associated with pain an fever then it is infection and inflammation. If it is hard, fixed and no pain the lymphoma and cancer.