Olecranon Bursitis: This condition, also known as "student's elbow," is characterized by inflammation of the bursa at the back of the elbow, leading to fluid accumulation. It's often caused by repetitive pressure on the elbow, such as leaning on a hard surface.

Elbow Fracture or Sprain: Trauma to the elbow can cause fluid accumulation due to bleeding or inflammation from the injury.
Rheumatoid Arthritis: This autoimmune disease can cause inflammation and fluid buildup in the joints, including the elbow.
Gout or Pseudogout: These conditions involve the deposition of crystals within the joints, leading to inflammation and fluid accumulation.
Infection (Septic Arthritis): Bacterial or fungal infections can cause fluid accumulation and inflammation in the elbow joint.

Septic Bursitis: An infection of the bursa can be serious and requires prompt antibiotic treatment. It may present similarly to olecranon bursitis but is a medical emergency.
Osteomyelitis: An infection of the bone can cause fluid accumulation and requires immediate medical attention.
Neoplastic Conditions: Although rare, tumors around the elbow can cause fluid accumulation and should not be missed.

Hemophilia: In patients with hemophilia, even minor trauma can lead to significant bleeding into the joints, including the elbow.
Sickle Cell Disease: This condition can cause vaso-occlusive crises, leading to joint pain and fluid accumulation.
Amyloidosis: A condition characterized by the deposition of amyloid proteins in various tissues, including joints, which can cause fluid accumulation.
Lipoma Arborescens: A rare condition involving the growth of fatty tissue within the joint, leading to fluid accumulation and joint damage.