To determine whether the morphology and incidence of subtypes of the fetal suprapatellar fold are different from those of adults. Materials and methods: Suprapatellar folds of 30 fetal knees (6 male and 9 female fetuses, ages varying between 20 and 34 weeks of gestation) were classified according to their morphological features. Results: In 33.3% of the knees, the suprapatellar fold was forming an apparent barrier between the suprapatellar bursa and the main articular cavity. Vertical parts of the mediopatellar fold in 3 fetuses and lateral fold in 4 fetuses were coursing as the continuation of the suprapatellar folds. The suprapatellar fold, as an almost complete membrane, was more frequent in fetuses compared with those of adults reported previously. Conclusion: Our findings support the fact that the suprapatellar folds of the knee joint in early periods of life are different than those of adults. We consider that the resorption of the mesenchymal tissue, particularly on the lateral part, continues until adulthood and causes alterations in the formation of intraarticular folds. The results of this preliminary study suggest that knee pain caused by impingement of the complete suprapatellar fold and intermittent painful swelling of the knee by a valvular mechanism may be encountered more frequently in early periods of life than in adulthood.

To determine whether the morphology and incidence of subtypes of the fetal suprapatellar fold are different from those of adults. Materials and methods: Suprapatellar folds of 30 fetal knees (6 male and 9 female fetuses, ages varying between 20 and 34 weeks of gestation) were classified according to their morphological features. Results: In 33.3% of the knees, the suprapatellar fold was forming an apparent barrier between the suprapatellar bursa and the main articular cavity. Vertical parts of the mediopatellar fold in 3 fetuses and lateral fold in 4 fetuses were coursing as the continuation of the suprapatellar folds. The suprapatellar fold, as an almost complete membrane, was more frequent in fetuses compared with those of adults reported previously. Conclusion: Our findings support the fact that the suprapatellar folds of the knee joint in early periods of life are different than those of adults. We consider that the resorption of the mesenchymal tissue, particularly on the lateral part, continues until adulthood and causes alterations in the formation of intraarticular folds. The results of this preliminary study suggest that knee pain caused by impingement of the complete suprapatellar fold and intermittent painful swelling of the knee by a valvular mechanism may be encountered more frequently in early periods of life than in adulthood.