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Year : 2022  |  Volume : 37  |  Issue : 3  |  Page : 180-182

Mucoid degeneration of the anterior cruciate ligament: A case study

Department of Orthopedics, Institute of Medical Sciences, Banaras Hindu University (BHU), Varanasi, Uttar Pradesh, India

Date of Submission08-Oct-2022
Date of Acceptance07-Nov-2022
Date of Web Publication15-Dec-2022

Correspondence Address:
Sanjay Yadav
Department of Orthopedics, Institute of Medical Sciences, Banaras Hindu University (BHU), Varanasi 221005, Uttar Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jbjd.jbjd_31_22

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Mucoid degeneration of anterior cruciate ligament (ACL) is a rare pathological condition characterized by knee pain and restriction of movements. In this condition, ACL is infiltrated by mucoid (glycosaminoglycans) like material within its substance. We discuss the case and present a review of literature including clinical and radiological features and management options. We encountered a 33-year-old female complaining of increasing pain in right knee since last 6 years with difficulty in squatting and sitting cross-legged. There was no history of significant trauma or instability of the knee. Clinical examination demonstrated pain on deep knee flexion, negative Lachman, and anterior drawer test. Plain radiograph of knee suggested early onset degenerative changes of knee in the form of medial joint space reduction. Magnetic resonance imaging (MRI) showed hyperintense signal in ACL substance in T1W and T2W images which is classically described as Celery Stalk appearance on T2 STIR images. This was often mistaken as partial tear of ACL. Patient was planned for diagnostic arthroscopy. During arthroscopy, ACL was occupying the whole intercondylar notch. It was hypertrophied, homogenous, and firm. Arthroscopic debulking of ACL was done cautiously and mucoid tissue was removed. The specimen was sent for histopathological examination which confirmed the diagnosis of mucoid degeneration. Post-operatively patient was relieved of symptoms and was doing well without any specific complaints like instability till last follow up at 18 months. Repeat MRI was not done as patient was not symptomatic. Mucoid ACL degeneration affects active persons in third to fourth decade of life without significant trauma. MRI is the most useful tool for diagnosis with specific findings. If this disease is considered preoperatively, it can be diagnosed early. Treatment with debulking or partial resection shows good functional results.

Keywords: ACL, arthroscopy, debulking, mucoid degeneration

How to cite this article:
Yadav S, Mittal V, Ojha A, Ansari W. Mucoid degeneration of the anterior cruciate ligament: A case study. J Bone Joint Dis 2022;37:180-2

How to cite this URL:
Yadav S, Mittal V, Ojha A, Ansari W. Mucoid degeneration of the anterior cruciate ligament: A case study. J Bone Joint Dis [serial online] 2022 [cited 2023 Feb 6];37:180-2. Available from: http://www.jbjd.in/text.asp?2022/37/3/180/363853

Mucoid degeneration of the anterior cruciate ligament (ACL) has been implicated as one of the factors responsible for knee pain.[1]

Kumar et al. first documented a case of biopsy-indicated ACL mucoid degeneration in 1999. Contrary to the previous reports of the rarity of the lesion, recent studies have revealed a relatively high prevalence.[2]

Etiological factors of mucoid degeneration of the ACL include repeated trauma to the ACL or degeneration of the ligament, chronic impingement of the ACL, synovial changes, and influence of anatomical variables such as the intercondylar notch of the knee and posterior tibial slope.[3]

In general, conservative treatment is the initial treatment of choice; however, if symptoms do not improve, arthroscopic partial resection/ debulking of the ACL can be performed.[4]

Mucoid degeneration of the ACL can be diagnosed based on magnetic resonance imaging (MRI) findings, gross observations, and histopathological examinations. MRI characteristics of ACL mucoid degeneration include ill-defined and thickened ligament, increased signal intensity and celery stalk sign, and intraoperative findings include ACL thickening, discharge of mucoid materials or loss of synovial lining, and impingement in full extension of the knee. Histopathological indications are increased collagen production and alterations in mucoid materials.[5]

  Anterior Cruciate Ligament Mucoid Degeneration Top

ACL mucoid degeneration is an uncommon pathological condition; the pathogenesis, prevalence, and association with other intra-articular knees structural damage are still poorly understood.[6]

It often presents with progressive knee pain, restriction in range of motion without a significant history of trauma, and without knee instability.

ACL mucoid degeneration was first described in 1999 based on biopsy findings. It is characterized by the degeneration of collagen fibers and the deposition of new glycosaminoglycans.

With the increasing use of MRI to evaluate the knee joint, ACL mucoid degeneration is increasingly being diagnosed incidentally when evaluating knees for pain and stiffness.[7] The prevalence of ACL mucoid degeneration on MRIs of the knee in two large series was 0.42% and 4.30%, respectively. The usual age group is fourth to fifth decade. It is more common in women.[8]

The pathogenesis of ACL mucoid degeneration is still unresolved, but injury, ganglion cyst, and the degenerative process leading to loss of the synovial lining of the ACL have been postulated.

It was also suggested that ACL degeneration in the young and athletic populations might be due to repeated microtrauma, while, in older patients, it could be due to a progressive degenerative ACL lesion with a concomitant degenerative meniscal lesion.

  Clinical Features Top

Insidious onset chronic knee pain behind the patella is the most common complaint. The duration of symptoms is variable from weeks to months. The pain may limit the terminal movements of the knee. There is usually no antecedent history of significant trauma, and when present, it is normally trivial. Pain and limitation in range of motion have been attributed to both increased volume and tension within the ligament and mechanical impingement with the unique function of the ACL in providing nociceptive sensory signals. Locking and grinding sensations may be present. Pain and knee stiffness do not respond to nonsteroidal anti-inflammatory drugs (NSAIDs) or physiotherapy.[9]

Clinical examination may show limitation of motion, joint line tenderness and joint effusion. The Lachman test, anterior drawer test, and pivot shift test for ACL integrity are usually negative. These clinical features should raise suspicion and the need for further evaluation with MRI (especially if the symptoms are nonspecific and unresponsive to NSAIDs and physiotherapy).

  Investigations Top

Conventional x-rays do not have any specific role in the diagnosis of ACL mucoid degeneration but will reveal associated osteoarthritic changes, if present. MRI is the mainstay of diagnostic imaging for mucoid degeneration. The MRI features suggestive of ACL mucoid degeneration are (a) abnormally thickened and an ill-defined, bulky ACL, (b) increased intra-ligamentous signals (intermediate signal intensity on T1-weighted images, high signal intensity on T2-weighted images, and proton density-weighted images) on all sequences interspersed among visible intact fibers (the celery stalk appearance), and (c) maintenance of normal orientation and continuity of the ACL [Figure 1].
Figure 1: Magnetic resonance imaging showing that the anterior cruciate ligament is bulky and has increased signal intensity and a celery stalk appearance

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ACL mucoid degeneration can coexist with ACL ganglion cyst, and there is a higher association of ACL mucoid degeneration with a meniscal tear, chondral damage, and intraosseous cyst at the femoral and tibial attachment of the ligament. ACL mucoid degeneration has been mistakenly reported as ACL rupture on MRI.[10]

  Treatment Top

Pain and limitation in the range of motion of the knee due to mucoid degeneration do not respond completely to NSAIDs and physiotherapy.

The interstitial nature of mucoid degeneration precludes guided aspiration as the treatment method.

Arthroscopic treatment with the aim of debulking the lesion without compromising the integrity of the ACL is the treatment of choice. On arthroscopy, the ACL mucoid cyst is viewed as homogenous and hypertrophied with increased diameter, intact and competent fibers with normal orientation, loss of shining synovial lining, the absence of ligamentous mucosa, and the flow of a yellow mucoid substance upon probing.[11]

Arthroscopic treatment consists of debridement and partial resection of the afflicted portion of the ACL, leaving intact the remnant of the anteromedial and posterolateral border and intact tibial and femoral attachment without impingement on the roof or lateral wall of the notch.[12]

Partial resection of the ACL results in immediate relief of pain and improvement in range of motion. The patient can immediately start full-weight-bearing and return to activity very soon.[13]

  Conclusion Top

Mucoid degeneration of ACL is a nontraumatic lesion that presents with chronic knee pain and limitation in the terminal range of motion of the knee. It usually has an insidious onset, without any history of significant trauma, and doesn’t respond to conventional NSAIDs and physiotherapy. This should be considered in the differential diagnosis of knee pain of unspecified origin. MRI is the gold standard for radiological diagnosis, and arthroscopic treatment results in prompt resolution of symptoms without compromising the integrity of the ligament.

Financial support and sponsorship

Not applicable.

Conflicts of interest

There are no conflicts of interest.

  References Top

Fealy S, Kenter K, Dines JS, Warren RF Mucoid degeneration of the anterior cruciate ligament. Arthroscopy 2001;17:1-4.  Back to cited text no. 1
Kumar A, Bickerstaff DR, Grimwood JS, Suvarna SK Mucoid cystic degeneration of the cruciate ligament. J Bone Joint Surg 1998;81:304-5.  Back to cited text no. 2
Maikano A, Pascual-Garrido C, Rolon A. Mucoid degeneration of the anterior cruciate ligament: MRI, clinical, intraoperative and histological findings. Knee Surg Sports Traumatol Arthrosc 2011;19:408-11.  Back to cited text no. 3
Lintz F, Pujol N, Boisrenoult P. Anterior cruciate ligament mucoid degeneration: A review of literature and management guidelines. Knee Surg Sport Traumatol Arthrosc 2011;19:1326-33.  Back to cited text no. 4
Matrawy KA, El-Nekeidy AM, Al-Dawody A Mucoid degeneration of the anterior cruciate ligament: Frequently under-diagnosed entity in MRI. Egypt J Radiol Nucl Med 2012;43:227-33.  Back to cited text no. 5
Pedrinell B, Castellana FB, Fontes RB. Anterior cruciate ligament: A case report. Sao Paulo Med J 2002;120:195-7.  Back to cited text no. 6
Kwee RM, Ahlawat S, Kompel AJ. Association of mucoid degeneration of anterior cruciate ligament with knee meniscal and cartilage damage. Osteoarthritis Cartilage 2015;23:1543-50.  Back to cited text no. 7
Salvati F, Rossi F, Limbucci N. Mucoid metaplastic-degeneration of anterior cruciate ligament. J Sports Med Phys Fitness 2008;48:483-7.  Back to cited text no. 8
Cha JR, Lee CC, Cho SD. Symptomatic mucoid degeneration of the anterior cruciate ligament. Knee Surg Sports Traumatol Arthrosc 2013;21:658-66.  Back to cited text no. 9
Chudasama CH, Chudasama VC, Prabhakar MM Arthrocopic management of mucoid degeneration of anterior cruciate ligament. Indian J Orthop 2012;46:561-5.  Back to cited text no. 10
Kim TH, Lee DH, Lee SH. Arthroscopic treatment of mucoid hypertrophy of the anterior cruciate ligament. Arthroscopy 2008;24:642-9.  Back to cited text no. 11
Pandey V, Suman CPS, Sharma S. Mucoid degeneration of anterior cruciate ligament: Management and outcome. India J Orthop 2014;48:197-202.  Back to cited text no. 12
Khanna G, Sharma R, Bhardwaj A Mucoid degeneration of the anterior cruciate ligament: partial arthroscopic debridement and outcomes. J Arthr Joint Surg. 2016;3:28–33  Back to cited text no. 13


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