Final answer:
The bursa in the knee helps reduce friction and cushion the joint. They allow smooth movement and prevent irritation or inflammation.
Step-by-step explanation:
A bursa is a fluid-filled sac that serves to prevent friction between skin, muscle, or tendon and an underlying bone. In the knee, there are several bursae that help reduce friction and cushion the joint. These include the prepatellar bursa located over the kneecap and the suprapatellar bursa that separates the tendon of the large anterior thigh muscle from the distal femur just above the knee. The bursae in the knee help the joint move smoothly and prevent irritation or inflammation.