Trauma: The most common cause of bruising around the elbow is trauma, which could be due to a fall onto the elbow, a direct blow, or repetitive strain. This is likely due to the elbow's susceptibility to injury during daily activities or accidents.

Hematoma: A collection of blood outside of blood cells, which can occur due to trauma or spontaneous bleeding, especially in individuals on anticoagulant therapy.
Vitamin Deficiencies: Deficiencies in vitamins like C or K can lead to easy bruising due to impaired collagen synthesis or blood clotting.
Bleeding Disorders: Conditions such as hemophilia or von Willebrand disease can cause easy bruising and bleeding due to defects in blood clotting factors.
Medication Side Effects: Certain medications, including anticoagulants, aspirin, and steroids, can increase the risk of bruising.

Abuse: In cases where the history does not match the injury, or in vulnerable populations such as the elderly or children, abuse must be considered as a cause of bruising.
Cancer: Certain types of cancer, such as leukemia or lymphoma, can cause easy bruising due to bone marrow suppression or platelet dysfunction.
Infection: Septic arthritis or osteomyelitis around the elbow can cause bruising, swelling, and pain, and requires prompt antibiotic treatment.
Vascular Disorders: Conditions like vasculitis or atherosclerosis can lead to bruising due to inflammation or obstruction of blood vessels.

Ehlers-Danlos Syndrome: A genetic disorder that affects connective tissue, leading to easy bruising, skin hyperextensibility, and joint hypermobility.
Scurvy: A disease caused by vitamin C deficiency, characterized by fatigue, malaise, and connective tissue defects, including easy bruising.
Amyloidosis: A condition characterized by the deposition of amyloid proteins in various tissues, which can cause bruising due to vascular fragility.
Henoch-Schönlein Purpura: A form of vasculitis that affects blood vessels and can cause bruising, typically in children.