The bursae of the knee are the fluid sacs and synovial pockets that surround and sometimes communicate with the joint cavity. Thin-walled and filled with synovial fluid, they represent the weak point of the joint, but also produce enlargements to the joint space. They can be grouped into either communicating and non-communicating bursae or, as below, after location.
In front there are five bursae:
the suprapatellar bursa or recess between the anterior surface of the lower part of the femur and the deep surface of the quadriceps femoris. It allows for movement of the quadriceps tendon over the distal end of the femur
the prepatellar bursa between the patella and the skin It allows movement of the skin over the underlying patella.
the deep infrapatellar bursa between the upper part of the tibia and the patellar ligament. It allows for movement of the patellar ligament over the tibia.
the subcutaneous infrapatellar bursa between the patellar ligament and skin.
the pretibial bursa between the tibial tuberosity and the skin. It allows for movement of the skin over the tibial tuberosity.
Laterally there are four bursæ:
the lateral gastrocnemius [subtendinous] bursa between the lateral head of the gastrocnemius and the joint capsule
the fibular bursa between the lateral (fibular) collateral ligament and the tendon of the biceps femoris
the fibulopopliteal bursa between the fibular collateral ligament and the tendon of the popliteus
and the subpopliteal recess (or bursa) between the tendon of the popliteus and the lateral condyle of the femur
Medially, there are five bursae:
the medial gastrocnemius bursa between the medial head of the gastrocnemius and the joint capsule
the anserine bursa between the medial (tibial) collateral ligament and the tendons of the sartorius, gracilis, and semitendinosus (i.e. the pes anserinus)
the bursa semimembranosa between the medial collateral ligament and the tendon of the semimembranosus
there is one between the tendon of the semimembranosus and the head of the tibia
and occasionally there is a bursa between the tendons of the semimembranosus and semitendinosus