The information provided here is not a replacement for a doctor. You shouldn't use it for the purpose of self-diagnosing or self-medicating but rather so you can have a more informed discussion with a professional TCM practitioner.
In Chinese Medicine knee weakness can be treated by two herbs that we have on record. Here is the list below.
The two Chinese Medicinal herbs most likely to help treat knee weakness
Why might Eucommia Leaf (Du Zhong Ye) help with knee weakness?
Because it is a herb specifically indicated to treat knee weakness as can be seen on Eucommia Leaf's page.
Eucommia Leaves is a Warm herb that tastes Pungent. It targets the Kidney and the Liver.
Its main actions are: Strengthens the Liver and the Kidneys
Why might Desert-Living Cistanche (Rou Cong Rong) help with knee weakness?
Because it is a herb specifically indicated to treat knee weakness as can be seen on Desert-Living Cistanche's page.
Desert-Living Cistanches is a Warm herb that tastes Salty and Sweet. It targets the Kidney and the Large intestine.
Its main actions are: Tonifies Kidney Yang, Restores Essence and Blood. Induces laxation.
Other symptoms often associated with knee weakness
Impotence Infertility Lower back pain Lower back weakness Knee pain Constipation Frequent urination Tinnitus Vertigo Sore lower back