Anterior cruciate ligament (ACL) mucoid degeneration, along with tears and anterior cruciate ligament ganglion cysts, is a relatively common cause of increased signal within the anterior cruciate ligament (ACL). The appearance can mimic acute or chronic interstitial partial tears of the ACL. However, in the case of mucoid degeneration secondary signs of ACL injury are usually absent. Secondary signs include bone bruising, meniscal tears, anterior subluxation of the tibia and other ligamentous injuries.
ACL mucoid degeneration is present on ~10% (range 9-12%) of 3 T MRI examinations and 2% of 1.5 T MRI examinations 6.
Typically patients present with knee pain or restricted movement, although often other potential causes for the patient's symptoms are found.
The pathogenesis remains controversial. Possible etiologies include:
- age-related (senescent) degeneration
- congenital or acquired synovial tissue entrapment between ACL fibres
It is postulated that mucoid degeneration may be a predisposing factor in the formation of ACL ganglion cysts.
On MRI, the ligament is thickened and ill-defined with a "celery stalk" appearance. Its signal is increased on all sequences. Intact fibres are best seen on T2-weighted sequences.
MRI is better at detecting mucoid degeneration than arthroscopy, as the surface of the ligament is often intact.
Treatment and prognosis
No treatment is usually required. If arthroscopy is performed, the ligament may appear entirely normal, especially using the standard anterior portal approach. A posterior approach will allow for the detection of changes by probing the ligament and mucoid material can be expressed.
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- 2. Bergin D, Morrison WB, Carrino JA et-al. Anterior cruciate ligament ganglia and mucoid degeneration: coexistence and clinical correlation. AJR Am J Roentgenol. 2004;182 (5): 1283-7. AJR Am J Roentgenol (full text) - Pubmed citation
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- 5. Cho SD, Youm YS, Lee CC et-al. Mucoid degeneration of both ACL and PCL. Clin Orthop Surg. 2012;4 (2): 167-70. doi:10.4055/cios.2012.4.2.167 - Free text at pubmed - Pubmed citation
- 6. Kwee, R., Hafezi-Nejad, N., Roemer, F., Zikria, B., Hunter, D., Guermazi, A. and Demehri, S. (2018). Association of Mucoid Degeneration of the Anterior Cruciate Ligament at MR Imaging with Medial Tibiofemoral Osteoarthritis Progression at Radiography: Data from the Osteoarthritis Initiative. Radiology, p.171565.
The knee is a complex synovial joint that can be affected by a range of pathologies:
- bone and cartilage
- distal femoral condyle fracture
- tibial plateau fracture (classification)
- patella fracture
avulsion fractures of the knee
- Segond fracture
- reverse Segond fracture
- anterior cruciate ligament avulsion fracture
- posterior cruciate ligament avulsion fracture
- arcuate complex avulsion fracture (arcuate sign)
- biceps femoris avulsion fracture
- iliotibial band avulsion fracture
- semimembranosus tendon avulsion fracture
- Stieda fracture (MCL avulsion fracture)
- patella fracture
- chronic avulsion injuries
- chondromalacia patellae
- osteoarthritis of the knee
- osteochondral defects
- osteochondritis dissecans of the knee
- pattern of bone contusion in knee injuries
- knee fractures
- anterior cruciate ligament tear
- anterior cruciate ligament ganglion cyst
- anterior cruciate ligament mucoid degeneration
- posterior cruciate ligament tear
- medial collateral ligament tear
- lateral collateral ligament tear
- medial patellofemoral ligament tear
- posterolateral corner injury
- posteromedial corner injury
- meniscal lesions
- meniscal tear
- meniscal/parameniscal cyst
- meniscal flounce
- meniscal fraying
- meniscocapsular separation
- synovial lesions
- fat pad
- popliteal fossa