Severe knee pain in osteoarthritis results from joint wear and inflammation, leading to stiffness and discomfort. Rest the knee, use a warm compress, do gentle strengthening exercises, and avoid strain, such as long standing or climbing, to reduce pain. Maintain a healthy weight, use supportive footwear, and keep your joints active within limits to improve function. Consult a doctor to suggest safe pain relief and guide proper long-term management for your condition.