There are many reasons for soft knees, common ones are chondromalacia patella, osteoarthritis of the knee joint, meniscus injury and so on.
1. Chondromalacia patella: after chronic damage to the cartilage surface of the patella, the cartilage appears to be swollen, eroded, cracked, broken, shedding and other changes in the formation of the patellofemoral joints of the osteoarthropathy, manifested in the knee after patellofemoral pain accompanied by knee joint softness, weakness and other symptoms.
2. Osteoarthritis of the knee: chronic joint disease characterized by degenerative lesions of knee cartilage and secondary osteophytes. As the disease progresses, patients will experience persistent joint pain, muscle atrophy, resulting in knee weakness, and often feel that the joints can not be completely straightened or impaired movement when walking.
3. Meniscus injury: a series of symptoms arising from the disruption of the integrity and continuity of the meniscus of the knee joint under different triggers, manifested as pain, swelling, joint popping, which may be accompanied by knee weakness or activity limitation and other symptoms.
There may be other reasons for knee weakness, such as over-exercise and knee free body, etc. If the symptoms persist with obvious pain, you should go to the hospital in time, and give targeted treatment after clarifying the cause of the disease.