Knee arthritis refers to the gradual breakdown of cartilage inside the knee joint. As this protective cartilage thins out, the bones start rubbing against each other. Consequently, patients experience pain, swelling, stiffness, and difficulty walking. Although the condition progresses slowly, it eventually restricts activities that once seemed easy—such as climbing stairs, squatting, or even walking short distances. Furthermore, knee arthritis includes multiple types. While osteoarthritis remains the most common, other forms such as rheumatoid arthritis and post-traumatic arthritis also cause significant damage. Because each type progresses differently, understanding them helps you choose the best treatment early.