Young people’s weak and tender knees may be caused by physiological factors such as strenuous exercise, but also may be due to meniscus injury, gouty arthritis and other pathological factors. 1. Strenuous exercise: due to strenuous exercise or prolonged fatigue and other factors, will directly lead to excessive lactic acid secretion in the body, the symptoms of muscle pain in the limbs, but also the phenomenon of knee weakness and softness, and will be gradually relieved by more rest. 2. Meniscus injury: when a large number of long-term exercise or improper exercise, will cause meniscus injury, long time without treatment will appear knee joint surface damage, will appear knee weakness symptoms. 3. Gouty arthritis: gouty arthritis is caused by urate deposition in the joint capsule and other tissues, if the body obesity, irregular diet and other reasons can lead to uric acid is too high, causing gouty arthritis, will lead to knee weakness and weakness of the phenomenon. When young people have knee weakness, they should go to the hospital in time, clarify the cause of the disease through examination, and actively cooperate with the doctor’s treatment.