The knee bursae are the fluid-filled sacs and synovial pockets that surround and sometimes communicate with the knee joint cavity. The bursae are thin-walled, and filled with

synovial fluid Synovial fluid, also called synovia, elp 1/sup> is a viscous, non-Newtonian fluid found in the cavities of synovial joints. With its egg white–like consistency, the principal role of synovial fluid is to reduce friction between the articular ...

. They represent the weak point of the joint, but also provide enlargements to the joint space. They can be grouped into either ''communicating'' and ''non-communicating'' bursae or, after their location – frontal, lateral, or medial.

Frontal

In front there are five bursae: # the suprapatellar bursa or recess between the anterior surface of the lower part of the

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...

and the deep surface of the

quadriceps femoris The quadriceps femoris muscle (, also called the quadriceps extensor, quadriceps or quads) is a large muscle group that includes the four prevailing muscles on the front of the thigh. It is the sole extensor muscle of the knee, forming a large ...

.Burgener (2002), p 390 It allows for movement of the quadriceps tendon over the distal end of the femur. In about 85% of individuals, this bursa communicates with the

knee joint In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the hu ...

. A distension of this bursa is therefore generally an indication of

knee effusion Knee effusion, informally known as water on the knee, occurs when excess synovial fluid accumulates in or around the knee joint. It has many common causes, including arthritis, injury to the ligaments or meniscus, or fluid collecting in the burs ...

. # the

prepatellar bursa The prepatellar bursa is a frontal bursa of the knee joint. It is a superficial bursa with a thin synovial lining located between the skin and the patella. Pathology Prepatellar bursitis, also known as housemaid's knee, is a common cause of s ...

between the

patella The patella, also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as m ...

and the

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

It allows movement of the skin over the underlying patella. # the deep infrapatellar bursa between the upper part of the

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

and the patellar ligament. It allows for movement of the patellar ligament over the tibia.Cipriano (2002), p 358. (A brief description of the "clinically important bursae in the anterior aspect of the knee") # the subcutaneous r superficialinfrapatellar bursa between the patellar ligament and skin. # the pretibial bursa between the

tibial tuberosity The tuberosity of the tibia or tibial tuberosity or tibial tubercle is an elevation on the proximal, anterior aspect of the tibia, just below where the anterior surfaces of the lateral and medial tibial condyles end. Structure The tuberosity o ...

and the skin. It allows for movement of the skin over the tibial tuberosity.

Lateral

Laterally there are four bursae: # the lateral gastrocnemius ubtendinousbursa between the lateral head of the

gastrocnemius The gastrocnemius muscle (plural ''gastrocnemii'') is a superficial two-headed muscle that is in the back part of the lower leg of humans. It runs from its two heads just above the knee to the heel, a three joint muscle (knee, ankle and subtalar ...

and the

joint capsule In anatomy, a joint capsule or articular capsule is an envelope surrounding a synovial joint.lateral (fibular) collateral ligament and the tendon of the

biceps femoris The biceps femoris () is a muscle of the thigh located to the posterior, or back. As its name implies, it has two parts, one of which (the long head) forms part of the hamstrings muscle group. Structure It has two heads of origin: *the ''long h ...

# the fibulopopliteal bursa between the fibular collateral ligament and the tendon of the

popliteus The popliteus muscle in the leg is used for unlocking the knees when walking, by laterally rotating the femur on the tibia during the closed chain portion of the gait cycle (one with the foot in contact with the ground). In open chain movements ...

# and the subpopliteal recess (or bursa) between the tendon of the popliteus and the lateral condyle of the femur

Medial

Medially, there are five bursae: # the medial gastrocnemius ubtendinousbursa between the medial head of the

and the joint capsule # the anserine bursa between the medial (tibial) collateral ligament and the pes anserinus – the conjoined tendons of the sartorius, gracilis, and

semitendinosus muscle The semitendinosus () is a long superficial muscle in the back of the thigh. It is so named because it has a very long tendon of insertion. It lies posteromedially in the thigh, superficial to the semimembranosus. Structure The semitendinosus, r ...

s. # the bursa semimembranosa between the medial collateral ligament and the tendon of the

semimembranosus The semimembranosus muscle () is the most medial of the three hamstring muscles in the thigh. It is so named because it has a flat tendon of origin. It lies posteromedially in the thigh, deep to the semitendinosus muscle. It extends the hip joint ...

# there is one between the tendon of the semimembranosus and the head of the tibia''Gray's Anatomy'' (1918) # and occasionally there is a bursa between the tendons of the semimembranosus and semitendinosus

Frontal

Lateral

Medial

See also

Notes

References

External links