Medial Epicondylitis (Golfer's Elbow): This condition is characterized by pain and inflammation on the medial (inner) aspect of the elbow, which could radiate to the antecubital space. The pain is often exacerbated by activities that involve flexion of the wrist, and it can be worse at night due to increased sensitivity or positions that put strain on the elbow.

Lateral Epicondylitis (Tennis Elbow): Although the pain is typically on the lateral (outer) side of the elbow, in some cases, it can radiate to the antecubital area. Night pain is common, especially if the elbow is flexed or the arm is in a position that stretches the affected tendons.
Cubital Tunnel Syndrome: This condition involves compression of the ulnar nerve as it passes through the cubital tunnel at the elbow. Symptoms can include pain, numbness, and tingling in the hand and forearm, with pain sometimes localized to the antecubital space, especially at night when the elbow is flexed.
Bursitis of the Elbow: Inflammation of the bursae around the elbow can cause pain and swelling, which might be felt in the antecubital space. The pain can be intermittent and worse at night, especially if the elbow is flexed or if there is direct pressure on the affected area.

Infectious Arthritis or Osteomyelitis: Although less common, infections in the elbow joint or bone can cause severe pain, which might be worse at night. These conditions require prompt diagnosis and treatment to prevent serious complications.
Neoplastic Processes: Tumors, either benign or malignant, in the bone, soft tissue, or nerve can cause deep, persistent pain that worsens at night. Early detection is crucial for effective management.
Vascular Conditions: Conditions affecting the blood vessels, such as thrombosis or aneurysms, can cause pain in the arm, including the antecubital space. These conditions can be serious and require immediate medical attention.

Rheumatologic Diseases: Certain autoimmune diseases, like rheumatoid arthritis or lupus, can cause elbow pain, although this is less common. The pain pattern can vary but might include night pain.
Nerve Entrapment Syndromes: Besides cubital tunnel syndrome, other nerve entrapments in the arm could potentially cause pain in the antecubital space, though this would be less typical.
Referred Pain from Other Sources: Pain from other areas, such as the neck or thoracic spine, can occasionally be referred to the elbow region, including the antecubital space, though this is less common.