Made of imported polymer materials, clear layers of skin and muscle, with integrated knee anatomical structure, and manifest body surface symbols Features: 1.  Can puncture repeatedly, standard puncture sites facilitate to acupuncture and there is realistic feeling when needle inserts into veins 2.  A single valve can inject simulated liquid of bursa mucosa into bursa mucosa repeatedly 3.  Automatic sealing of bursa mucosa 4.  Skin surface can be cleaned by suds