Lymphedema: This condition is characterized by the abnormal accumulation of protein-rich fluid in the interstitial tissue, leading to swelling. It can be primary (idiopathic) or secondary to surgery, infection, or trauma, although trauma is not present in this case. The absence of trauma, joint pain, or redness makes lymphedema a plausible explanation for unilateral hand edema.

Cellulitis: Although the question specifies no redness, early or mild cases of cellulitis might not present with the typical signs of inflammation. It's an infection of the skin and subcutaneous tissues, usually caused by bacteria, and can cause edema.
Deep Vein Thrombosis (DVT): DVT can cause swelling in one limb due to the obstruction of blood flow. The absence of pain does not rule out DVT, as it can be asymptomatic or present with minimal symptoms.
Venous Insufficiency: This condition occurs when the veins have problems returning blood from the legs or arms to the heart due to valve issues. It can lead to edema, among other symptoms.

Compartment Syndrome: Although typically associated with trauma and pain, compartment syndrome is a medical emergency that can occasionally present atypically. It involves increased pressure within a muscle compartment, leading to muscle and nerve damage.
Neoplasm: Tumors, either benign or malignant, can cause edema by obstructing lymphatic or venous drainage. While less common, this diagnosis is critical not to miss due to its implications for treatment and prognosis.
Infection (e.g., Abscess): An abscess or other localized infection could potentially cause edema without significant redness or pain, especially in early stages or in immunocompromised patients.

Sarcoidosis: A systemic disease that can affect multiple parts of the body, including the skin, and cause edema among other symptoms.
Filariasis: A parasitic disease caused by an infection with filarial parasites, which can lead to lymphedema.
Thyroid Disease: Both hypothyroidism and hyperthyroidism can lead to edema, though it's typically more generalized than unilateral.
Fabry Disease: A rare genetic disorder that can cause edema due to the accumulation of a particular type of fat in the body's cells.