Lateral Epicondylitis (Tennis Elbow) and Medial Epicondylitis (Golfer's Elbow): Given the patient's manual job, repetitive strain on the elbows is likely, leading to these overuse injuries. The absence of swelling or redness does not rule out these conditions, as they often present with pain as the primary symptom.

Bursitis: Although there's no swelling mentioned, bursitis (especially olecranon bursitis) could cause elbow pain and might not always present with significant swelling or redness, especially in early stages.
Tendinosis: Similar to epicondylitis, tendinosis (degeneration of the tendons) can cause chronic pain without significant inflammation.
Repetitive Strain Injury (RSI): Given the patient's manual job, RSI is a plausible diagnosis, as it encompasses a range of conditions caused by repetitive movements.

Rheumatoid Arthritis (RA): Although less likely given the absence of swelling or redness, RA can cause bilateral elbow pain and is a condition that should not be missed due to its significant impact on quality of life and the importance of early treatment.
Osteoarthritis: While more common in older adults, osteoarthritis could cause bilateral elbow pain, especially if there's a history of trauma or repetitive strain.
Infection (Septic Arthritis): Although unlikely without signs of infection like redness, warmth, or swelling, septic arthritis is a medical emergency and should always be considered, especially if the patient has a fever or recent history of infection.

Amyloidosis: A rare condition that can cause joint pain, including elbow pain, though it's much less common and typically associated with other systemic symptoms.
Sarcoidosis: Can cause joint pain and might affect the elbows, though it's rare and usually accompanied by other symptoms like lung involvement or skin lesions.
Gout or Pseudogout: Although these conditions more commonly affect the lower extremities, they can cause elbow pain and should be considered, especially if there's a history of similar conditions or renal issues.