The ligamentum mucosum - also known as the infrapatellar plica - is a flimsy band of tisse stretching across the front of the knee between the femur bone and the fat pad behind the kneecap.
The knee joint opened up to reveal the various plicae including the ligamentum mucosum.
Side view of the knee, showing how the ligamentum mucosum is related to the fat pad and is situated in front of the more substantial anterior cruciate ligament.
Ligamentum mucosum and anterior knee pain
The intimate relationship between the ligamentum mucosum and the fat pad means that the structure can be stretched as the knee bends and straightens. If the composite is compromised either by injury or a growth spurt, pain may be experienced in the front of the knee.
Arthroscopic Untethering of the Fat Pad of the Knee: Release or Resection of the Infrapatellar Plica (Ligamentum Mucosum) and Related Structures for Anterior Knee Pain. Smallman TV, Portner OT, Race A, Shekitka K and Mann K. Arthrosc Tech. 2018 May; 7(5): e575–e588.
The biomechanical and morphological characteristics of the ligamentum mucosum and its potential role in anterior knee pain. Norris M, Corbo G, Banga K, Johnson M, Sandig M, Smallman T, Getgood A and Burkhart TA. Knee. 2018 Dec;25(6):1134-1141. doi: 10.1016/j.knee.2018.08.017. Epub 2018 Nov 8.