"Jnana" means knowledge. "Asana" means yoga posture.
Patanjli's, Yoga Sutra, written in 2nd century BC states- "Where there is Asana, there should be Dhyana. Where there is Dhyana, there should be Asana".
Yoga is union of body (by asanas) and mind (by meditation/Dhyana). Yoga is not merely a physical exercise. In fact, practice in such a way that the mind, intelligence and consciousness are continuously in touch with the movements of the body. There has to be a homogeneous approach which involves body, mind and self to find an even balance of attention , extension and expansion in the body, mind and Self. Such a complete practice is called Sadhana.
Sadhna is a key concept. It implies effort, but actually the sense of effort goes beyond it. It demands an examining but a disassociated mind. When the effortful efforts transform into an effortless state then one experiences the calm and steadiness in a pose. This ultimate experience of union of body and mind should be the goal of everyone who practice yoga and is achieved after years of disciplined practice. This is Dhyana in Asana.
Furthermore, it is impossible to meditate (Dhyana) without taking a correct position and staying still and comfortable in that position. This is Asana in Dhyana.
Every asana has three movements- Going into position, stabilizing and staying in the asana and coming out of the position. In this way, an asana mentally expresses the three parts of the mantra "Aum", without actually uttering it. ! We all start by doing asanas from the gross body(physical body) and eventually move to through to the subtle body (physiological body) to the causal body (spiritual body). Once there, the practice becomes mediation in action.
Perform the asanas without any expression of physical ego and without seeking comfort and ease. Do not let your mind surrender to the dictating body and become its slave. Instead the asanas must be done using the body as an instrument to explore the hidden weaknesses of the body and mind.
So, remove any misconception that dhyana is spiritual yoga and asana is physical yoga. They both go together and are part of a whole, which is YOU.