Osteoarthritis is a degenerative joint disease where protective cartilage between bones gradually erodes, causing pain, stiffness, and limited mobility. It most often affects the knees, hips, spine, and small joints of the hands. Diagnosis relies on physical examination, patient history, and imaging such as X-rays or MRI to assess cartilage loss and bone changes. Treatment options span anti-inflammatory medications, structured physical therapy, corticosteroid injections, and surgical joint replacement for severe cases. Recognizing early symptoms and consulting a rheumatologist promptly can significantly slow disease progression and preserve long-term joint function.