Why does my leg not hurt when walking on flat ground, but hurts when going upstairs?

Generally, leg pain that occurs when climbing stairs but not while walking on flat ground may be caused by decreased joint flexibility, insufficient muscle strength, meniscus injury, knee synovitis, or osteoporosis. If abnormal symptoms occur, it is recommended to seek timely medical evaluation at a hospital to determine the underlying cause and receive targeted treatment. Specific causes are analyzed as follows:

1. Decreased Joint Flexibility

When joint flexibility declines, the motion of climbing stairs increases stress on the joints, leading to pain. Appropriate range-of-motion exercises such as yoga and stretching can help improve joint flexibility.

2. Insufficient Muscle Strength

Climbing stairs requires leg muscles to support body weight and propel the body upward. When muscle strength is inadequate, muscles fatigue more easily during activity, causing soreness. Regular strength-training exercises such as squats and stair climbing can enhance leg muscle strength.

3. Meniscus Injury

Meniscus injuries can result from compression or pre-existing conditions affecting the meniscus. The meniscus is a cartilage pad within the knee joint; when damaged, its stability and shock-absorbing functions are compromised. This leads to uneven pressure distribution in the knee during stair climbing, potentially causing pain along with swelling and a catching sensation. Initial treatment is conservative, including rest, ice application, and limb elevation to reduce inflammation and swelling. If symptoms persist or worsen, arthroscopic surgery may be required.

4. Knee Synovitis

Knee synovitis occurs when the synovial membrane becomes inflamed due to irritation, resulting in increased joint fluid, swelling, and pain. During stair climbing, friction and compression in the knee joint can exacerbate the inflammatory response of the synovium, leading to pain, swelling, effusion, and restricted movement. Treatment may include medications such as loxoprofen sodium tablets, ibuprofen sustained-release tablets, or celecoxib capsules, used under a doctor's guidance.

5. Osteoporosis

Osteoporosis is a systemic skeletal disease characterized by reduced bone mass and deterioration of bone microstructure. When climbing stairs, the bones are subjected to greater pressure and load, making osteoporotic bones more susceptible to microscopic fractures or cracks, which can cause pain. Other symptoms may include back pain and kyphosis (hunched posture). It is generally recommended to take calcium supplements such as calcium carbonate D3 granules or calcium gluconate oral solution, along with vitamin AD soft capsules, as directed by a physician.

In daily work and life, it is important to avoid maintaining prolonged sitting or standing positions. Regular physical activity and periodic relaxation of muscles and joints can help maintain skeletal health.