Which condition is characterized by inflammation of the bones at the joints?

The condition characterized by inflammation of the bones at the joints is arthritis. Arthritis is an umbrella term that encompasses various inflammatory joint diseases, leading to swelling, pain, and stiffness in the affected areas. This inflammation can affect one or multiple joints and is not limited to a specific type of arthritis, making it a broad descriptor.

Rheumatoid arthritis, while also an inflammatory condition, specifically refers to an autoimmune form of arthritis that can lead to joint damage and other systemic issues. Osteoporosis is primarily a condition concerning bone density loss, not directly about inflammation at the joints, and tendinitis involves inflammation of the tendons rather than the joints themselves. Therefore, arthritis is the most accurate choice that encompasses the general characteristic of joint inflammation.