Knee bursae

The knee bursae are sacs surrounding the knee joint that are filled with synovial fluid. They facilitate movement and reduce friction where tendons or muscles pass over bony prominences. The knee bursae can be either communicating or non-communicating with the knee joint itself. 

Gross Anatomy

There are four bursae anterior to the knee joint:

• suprapatellar bursa - between the femur and quadriceps femoris, it is attached to the articularis genu muscle and communicates with the synovial cavity
• subcutaneous prepatellar bursae - between the skin and patella
• subcutaneous infrapatellar bursae - between the skin and tibial tuberosity
• deep infrapatellar ligament - between patella ligament and upper tibia

Two bursae are located laterally:

• between the lateral collateral ligament and the biceps femoris tendon
• between the lateral collateral ligament and the capsule where it overlies the popliteus muscle

Two bursae are located medially: 

• between the medial collateral ligament and the pes anserinus
• between the medial collateral ligament and the capsule, tibia and semimembranosus tendon

There are four bursae posterior to the knee joint:

• between capsule and medial head of gastrocnemius; communicates with the synovial cavity
• semimembranosus bursa - between semimembranosus and the medial head of gastrocnemius; may communicate with the bursa under the medial head of the gastrocnemius and thereby the synovial cavity
• between capsule and lateral head of gastrocnemius; may communicate with the synovial cavity in some people
• between popliteus tendon and posterior tibia and fibula; communicates with the synovial cavity¹

Related Pathology 

• pes anserinus bursitis
• bursitis
• pigmented villonodular bursitis