Lateral Epicondylitis: This is the most common cause of tennis elbow, characterized by inflammation of the tendons that attach to the lateral epicondyle of the humerus. It is often related to overuse or repetitive strain on the forearm extensors.

Radial Tunnel Syndrome: This condition involves compression of the radial nerve as it passes through the radial tunnel in the forearm, leading to pain and weakness in the wrist and hand extensors.
Cervical Radiculopathy: Referral pain from the cervical spine, particularly from C6 or C7 nerve roots, can mimic tennis elbow symptoms, including pain and weakness in the arm and forearm.
Elbow Osteoarthritis: Degenerative changes in the elbow joint can cause pain and stiffness, potentially mimicking the symptoms of tennis elbow.

Fracture of the Radial Head or Neck: An acute fracture in this area can cause severe pain and limited mobility, which might be mistaken for tennis elbow. Missing this diagnosis could lead to improper healing and long-term disability.
Infection (Osteomyelitis or Septic Arthritis): Although rare, infections around the elbow can present with pain and swelling, similar to tennis elbow. Failing to diagnose and treat an infection promptly can lead to serious complications.
Tumor (Bone or Soft Tissue): A tumor in the elbow region could cause chronic pain and might be overlooked in favor of more common diagnoses like tennis elbow. Missing a tumor could have significant implications for treatment and prognosis.

Gout or Pseudogout: These conditions can cause acute, severe pain and swelling in the elbow, although they are less common in this joint compared to others like the big toe.
Bursitis (Olecranon or Radial): Inflammation of the bursae around the elbow can cause pain and swelling, which might be confused with tennis elbow symptoms.
Entrapment Neuropathy (Posterior Interosseous Nerve): This is a rare condition where the posterior interosseous nerve, a branch of the radial nerve, becomes compressed, leading to pain and weakness in the forearm and wrist.