Anatomy, Biomechanics, and Surgical Approach to Synovial Folds Within the Joints of the Foot

Abstract

The presence of synovial folds in various joints of the foot has been previously documented. The function and clinical significance of these structures within the joint have not been established. Histologically they are considered anatomically different from a meniscus primarily owing to their makeup of loose connective tissue with nerve fibrils and several synovial cell layers. We hypothesize that the function of these folds is similar to that of the menisci: to increase joint congruity and stability. We further hypothesize that these folds will be present in joints of the foot that require greater stability. To demonstrate this, 41 fixated cadaveric feet were sectioned in the sagittal plane and the incidence and locations of the synovial folds were documented. Three fixated cadaveric feet were evaluated using a materials testing machine. The first metatarsophalangeal joint was incised, and the presence of the synovial fold was documented. The joint was then taken through its range of motion with and without the synovial fold while data on the force and displacement were collected. The steps were then repeated for the ankle joint. The results showed statistically stiffer ankle and first metatarsophalangeal joints with the synovial fold present, as determined by the stress-strain curve. On the basis of the presence and location of these synovial folds, we demonstrated arthroscopic surgical approaches to many of the documented joints that contain these folds. Because the folds contain synovial cells and vascular tissue, damage to them can result in considerable pain. In such cases, arthroscopic surgery would be of benefit. Further research may indicate whether they need to be salvaged during joint procedures to facilitate normal joint function or should be removed to reduce postoperative complications.