Synovial Fluid Circulation in the Hip

Traveling through England and Wales with apologies for the tardiness and brevity of posts.

Synovial tissue in the hip is predominantly located in the peripheral compartment; however, the central compartment, where the articular cartilage of the femoral head and acetabulum reside, is where the lubrication of the synovial fluid is needed.

The peripheral compartment consists of proximal and distal zones. These two zones are separated from each other by the zona orbicularis, the deep circular fibers of the ischiofemoral ligament.

On hip flexion, the transverse ligament separates from the femoral head and synovial fluid flows from the peripheral compartment into the acetabular notch (cotyloid fossa). On hip extension, fluid passes across the articular surface and pools adjacent to the labrum and in the labro-chondral sulcus. The movement of the zona orbicularis serves as a bellows to drive synovial fluid, and the labrum acts as a reservoir to delay return of fluid to the peripheral compartment.

References

Field RE, Rajakulendran K. The labro-acetabular complex. J Bone Joint Surg Am. 2011 May;93 Suppl 2:22-7.