Osteoarthritis (OA): Given the patient's age, moderate osteoarthritis, degenerative changes, joint space narrowing, and periaricular osteophyte formation, OA is the most likely diagnosis. These findings are classic for OA, which is a common condition in older adults.

Degenerative Joint Disease: This is essentially synonymous with osteoarthritis and refers to the wear and tear of the joint over time, leading to symptoms and radiographic findings similar to those described.
Spondyloarthritis: Although less likely given the absence of specific findings like sacroiliitis or syndesmophytes, spondyloarthritis could present with similar degenerative changes, especially if the patient has a history of back pain or inflammatory symptoms.
Psoriatic Arthritis: Without skin changes or specific radiographic findings like pencil-in-cup deformities, this is less likely, but it remains a consideration, especially if there's a history of psoriasis or nail changes.

Infection (Septic Arthritis): Although there's no joint effusion mentioned, which is a common finding in septic arthritis, it's crucial not to miss this diagnosis due to its potential for rapid joint destruction and systemic complications. The absence of a joint effusion does not rule out infection.
Malignancy (e.g., Metastatic Disease): No focal osseous lesions are mentioned, but it's essential to consider malignancy, especially in an older adult, as metastatic disease can present with a variety of skeletal findings, including degenerative changes that might mimic or coexist with OA.
Gout or Pseudogout: These conditions can cause acute inflammatory arthritis and may lead to chronic changes that resemble OA. The absence of joint effusion or specific radiographic findings like tophi in gout does not rule out these diagnoses entirely.

Hemochromatosis: A genetic disorder leading to iron overload, which can cause arthropathy that resembles OA, particularly in the second and third metacarpophalangeal joints.
Wilson's Disease: A rare genetic disorder that leads to copper accumulation, which can cause liver disease, neurological symptoms, and an arthropathy that might mimic OA.
Acromegaly: Caused by excess growth hormone, leading to soft tissue and bony changes, including an arthropathy that can resemble OA, especially if the condition develops in adulthood.