Rheumatoid Arthritis (RA): This is the most likely diagnosis given the bilateral nature of the arthralgia, which is more consistent with an autoimmune process like RA. RA typically presents with symmetric joint involvement, morning stiffness lasting more than an hour, and can include systemic symptoms.

Osteoarthritis (OA): Although less likely given the bilateral and symmetric nature of the symptoms, OA can occasionally present in a more generalized form, especially in older adults. However, OA typically affects weight-bearing joints and the hands in an asymmetric pattern.
Systemic Lupus Erythematosus (SLE): SLE can cause arthralgias and arthritis that may mimic RA. The presence of other systemic symptoms such as skin rashes, renal involvement, or hematologic abnormalities would support this diagnosis.
Psoriatic Arthritis (PsA): PsA can cause a variety of joint symptoms, including oligoarticular or polyarticular patterns. The presence of psoriasis, nail changes, or dactylitis would suggest this diagnosis.

Septic Arthritis: Although less common, septic arthritis is a medical emergency that requires prompt diagnosis and treatment. It typically presents with acute onset of pain, swelling, and decreased range of motion in a single joint, but can be bilateral in the case of certain infections (e.g., gonococcal arthritis).
Lyme Arthritis: Caused by Borrelia burgdorferi, Lyme disease can lead to arthritis, typically affecting the knee. Early stages of Lyme disease can present with systemic symptoms and a characteristic rash (erythema migrans).
Gout or Pseudogout: These crystal-induced arthropathies can cause acute, severe joint pain and can occasionally present in a polyarticular fashion, especially in older adults or those with renal impairment.

Relapsing Polychondritis: A rare autoimmune disorder characterized by recurrent episodes of cartilaginous inflammation, which can affect the ears, nose, trachea, and joints.
Sjögren's Syndrome: An autoimmune disorder that primarily affects the exocrine glands, particularly the salivary and lacrimal glands, but can also cause arthralgias and arthritis.
Hemochromatosis: A genetic disorder leading to iron overload, which can cause arthropathy, typically affecting the second and third metacarpophalangeal joints, similar to OA.