A seven-year old male German shepherd is presented with a history of weakness in the hind limbs, urinary incontinence and recent obsessive chewing around his tail area.Dorsiflexion of the tail over the back and extension of the hind limbs elicits a painful response. He does not withdraw each hind leg when a toe is pinched, but bears weight on the hindlimbs. Patellar reflexes are normal.What is the clinical diagnosis?
一只7岁的雄性德国牧羊犬出现后肢无力，尿失禁和近期咬尾巴附近的表现。把尾巴弯到背部和拉伸后肢会引起疼痛反应。当用力按压脚趾，后腿没有收回反射，但他后肢可以负重。 膝跳反射是正常的。临床诊断是什么？