The ligamentum mucosum - also known as the infrapatellar plica - is a flimsy band of tissue stretching across the front of the knee between the femur bone and the fat pad behind the kneecap.
Page updated March 2024 by Dr Sheila Strover (Clinical Editor)
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.
What is the function of the ligamentum mucosum?
Until fairly recently the ligamentum mucosum has been considered a useless embryological remnant.
However, a number of fairly recent anatomical studies have shown that there is quite considerable variability in its structure, and there is speculation that it does serve a purpose.
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 this composite is compromised either by injury or a growth spurt, pain may be experienced in the front of the knee.
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Quote from peer-reviewed paper:
"Anterior knee pain (AKP), a multifactorial symptom complex, can be successfully treated surgically. A specific diagnosis often cannot be made, but the pain is linked to an unrecognized common factor in most patients: ...the fat pad (FP) and infrapatellar plica (IPP)."
Citation: Smallman TV, Portner OT, Race A, Shekitka K, Mann K. 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. Arthrosc Tech. 2018 Apr 30;7(5):e575-e588. doi: 10.1016/j.eats.2018.02.002. PMID: 29942735; PMCID: PMC6011586.
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Quote from peer-reviewed paper:
"Infrapatellar plica injury is an under-reported cause of anterior knee pain"
Citation: Singh DK, Rajani H, Sinha M, Katyan A, Suman S, Mishra A, Nayak BK. Infrapatellar plica injury: Magnetic resonance imaging review of a neglected cause of anterior knee pain. SA J Radiol. 2021 Feb 19;25(1):1973. doi: 10.4102/sajr.v25i1.1973. PMID: 33824739; PMCID: PMC8008011.
Forum discussions
- "Re: Introduction"
Helping patients access the medical literature about the fat pad and the ligamentum mucosum.
Relevant material -
Authoritative course -
2018 - An alternative viewpoint on Anterior Knee Pain - by Dr Thomas Smallman (Knee Surgeon)