Bursae are small, fluid-filled sacs found throughout the human body, acting as natural cushions. These sacs are positioned in areas where tissues, such as bones, tendons, and muscles, rub against each other during movement. Their primary role is to reduce friction and facilitate smooth, unhindered motion.
Understanding Bursae
A bursa is a thin, closed sac lined by a synovial membrane, containing lubricating synovial fluid. Bursae provide a smooth, gliding surface, preventing friction and cushioning pressure points between anatomical structures, allowing tissues to move past one another with ease. While some bursae are present from birth, others can develop later in life in response to repeated friction or pressure on certain body areas.
Knee Bursae: Locations and Functions
The knee joint, being a major weight-bearing and highly mobile joint, contains several important bursae that protect it during movement. These bursae are crucial for ensuring smooth motion and minimizing wear between bones, tendons, and skin.
One prominent bursa is the prepatellar bursa, located directly in front of the kneecap (patella), between the skin and the patella itself. Its function is to allow the skin to glide smoothly over the kneecap as the knee bends and extends, reducing friction during kneeling. Another set of bursae, the infrapatellar bursae, are found below the kneecap. The superficial infrapatellar bursa lies between the patellar ligament and the skin, while the deep infrapatellar bursa is situated between the patellar ligament and the shinbone (tibia). Both infrapatellar bursae help cushion the patellar tendon and reduce friction during knee movement, particularly during activities involving bending and extending the knee.
The pes anserine bursa is located on the inner side of the knee, approximately 2 to 3 inches below the joint line. It is positioned between the shinbone (tibia) and the conjoined tendons of three hamstring muscles: the sartorius, gracilis, and semitendinosus, which together form the pes anserinus (meaning “goose’s foot”). This bursa reduces friction and cushions these tendons as they glide over the tibia, especially during knee flexion and rotation.
Addressing Knee Bursa Issues
When a bursa becomes inflamed, the condition is known as bursitis. In the knee, bursitis typically results from repetitive pressure, overuse, direct trauma, or, less commonly, infection. For instance, prolonged kneeling can irritate the prepatellar bursa, leading to what is sometimes called “housemaid’s knee” or “carpet layer’s knee.” Similarly, activities involving repetitive knee bending or jumping can irritate the infrapatellar or pes anserine bursae.
Symptoms of knee bursitis often include localized pain, swelling, tenderness to the touch, and warmth over the affected area. The swelling can sometimes be quite noticeable and feel squishy. While pain might be constant, it often worsens with movement or direct pressure. In cases of infectious bursitis, additional symptoms like redness, fever, or chills may be present.
Management of knee bursitis begins with conservative approaches to reduce inflammation and pain. Rest involves avoiding activities that aggravate the knee. Applying ice, compression, and elevating the leg can help reduce swelling and discomfort. Over-the-counter pain relievers can alleviate pain and inflammation. Physical therapy exercises, focusing on strengthening muscles and improving flexibility, are also beneficial for managing symptoms and preventing recurrence.