Sitting on your knees is a posture where you kneel, folding your legs beneath you so your buttocks rest on your heels and the tops of your feet are flat on the floor. This position, known as Seiza in Japanese culture or Vajrasana (Thunderbolt Pose) in yoga, is common in practices focusing on meditation and digestion. It forces both the knee and ankle joints into deep flexion, an action rarely sustained in modern chair-sitting life. This unique position has complex and contrasting effects on the body, offering certain benefits while also posing potential strain.
Stress on Knees and Ankles
The knee joint is forced into maximum flexion, which can irritate the cartilage beneath the kneecap, especially if the sitting surface is hard. This deep bend compresses the menisci and increases the pressure within the joint space, a condition that can worsen pre-existing knee issues like patellofemoral syndrome or osteoarthritis. Prolonged periods in this posture are particularly taxing, as the lack of movement prevents the proper circulation of synovial fluid, the joint’s natural lubricant.
The ankle joint is also subjected to extreme plantarflexion, where the toes are pointed away from the shin. This position places the weight of the upper body directly onto the ankle and surrounding tissues, which creates considerable stress. While regular, short practice may improve flexibility and range of motion, extended use can be damaging. Individuals with tight hip flexors or quadriceps muscles may find the knee’s ability to bend is restricted, causing discomfort and increased pressure in the joint.
Effects on Blood Flow and Nerves
The deep folding of the lower limbs creates a tourniquet-like effect that significantly impacts circulation. The body’s weight compresses arteries and veins in the lower legs, restricting blood flow to the muscles and tissues below the knee. This reduction in circulation can lead to a temporary lack of oxygen, often experienced as “pins and needles” or temporary numbness.
The position can also place direct pressure on nerves, most notably the common peroneal nerve. This nerve wraps around the outside of the knee near the head of the fibula, making it vulnerable to compression. Sustained pressure can cause temporary symptoms like tingling, numbness, or weakness in the foot and lower leg. While temporary restriction is reversed quickly upon changing position, persistent loss of sensation is a warning sign.
Postural and Digestive Benefits
Beyond the strain on the joints, this posture offers benefits for the upper body and internal systems. Sitting on your knees naturally encourages a straight spine, as the pelvis is stabilized and the base of support is fixed. This alignment helps to counteract the common tendency to slouch in a chair, promoting better overall posture and potentially alleviating lower back pain. The sustained erect posture gently engages the core muscles, which contributes to spinal stability over time.
The unique feature of this posture is its effect on the digestive system. It is one of the few postures recommended immediately after a meal in some traditions. The position is thought to improve digestion by diverting blood flow away from the lower limbs and toward the abdominal area. This shift in circulation, combined with mild compression on the abdomen, is believed to stimulate peristalsis, helping to reduce flatulence and acidity.
When to Avoid This Position
Individuals with severe arthritis, recent knee or ankle surgery, or acute joint pain should completely avoid this position, as the deep flexion can exacerbate existing damage. Similarly, people at risk for deep vein thrombosis (DVT) should not use this posture due to the prolonged, restrictive compression of blood vessels in the lower legs.
If the position causes pain, a sharp sensation, or prolonged numbness, stop immediately. For those who wish to practice safely, simple modifications can significantly reduce pressure. Placing a folded blanket or firm pillow between the buttocks and the heels decreases the degree of knee and ankle flexion. A specialized Seiza bench allows the weight to rest on the bench rather than the joints, providing the benefits of the upright posture without joint compression.