Feeling tired and weak, along with knee pain and tenderness, can happen due to many reasons, such as vitamin D or B12 deficiency, low calcium levels, anaemia, joint strain, early arthritis, or even lack of physical activity, and sometimes inflammation in the joints can also make movement painful and stiff. When the body is low in essential nutrients or the muscles around the knee become weak, daily activities can start feeling more difficult and tiring. It is important to avoid overusing the joint for now and give it proper rest while still doing very gentle movements to prevent stiffness. Warm compresses can help reduce discomfort, and maintaining a balanced diet with enough protein, calcium-rich foods, and hydration may support recovery. Regular light walking, once pain reduces, can also help improve strength around the knee. Medicines/treatment should be taken only if advised or prescribed by your doctor. If pain is increasing, swelling is present, or you are unable to walk properly, a medical evaluation is important to check for arthritis, deficiency, or other joint-related conditions.