Final answer:
The nurse avoids pressure on the back of a patient's knees post-surgery to prevent the development of deep vein thrombosis (DVT), a blood clot in a deep vein caused by immobility and decreased skeletal muscle pump activity.
Step-by-step explanation:
The nurse avoids putting pressure on the back of the client's knees after surgery to prevent the complication of deep vein thrombosis (DVT). DVT is a condition where a blood clot forms in a deep vein, typically in the legs, which can be dangerous if it dislodges and travels to the lungs. The risk of DVT increases with prolonged bed rest and immobility because the skeletal muscle pump is less active, allowing blood to pool and clot in the veins. Ensuring that there is no pressure on the client's knees helps maintain proper circulation and reduces the risk of DVT.