Table of Contents  
Year : 2015  |  Volume : 8  |  Issue : 6  |  Page : 785-787  

Magnetic resonance imaging of cyclops lesion as a cause of persistent morbidity after anterior cruciate ligament reconstruction

Department of Radiodiagnosis, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pune, India

Date of Web Publication19-Nov-2015

Correspondence Address:
Amit Kharat
Flat 1101, C wing, Dew Drops Society, New Alandi Road, Vishranwatwadi, Pune - 411 015, Maharashtra
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0975-2870.169932

Rights and Permissions

Localized anterior arthrofibrosis (cyclops lesion) is having around 1-9.8% frequency rate after anterior cruciate ligament (ACL) reconstruction. It has been reported to be a significant cause of loss of knee extension after reconstruction of the ACL of the knee. We present a case report of a patient with prior ACL reconstruction who presented with pain and loss of extension following surgery. MR imaging revealed the typical features of cyclops lesion. Repeat arthroscopy excision of the lesion is the only treatment to reduce the morbidity of the patient.

Keywords: Anterior cruciate ligament, arthroscopy, cyclops lesion, localized anterior arthrofibrosis, magnetic resonance imaging

How to cite this article:
Kharat A, Garg S, Singh A, Kulkarni V. Magnetic resonance imaging of cyclops lesion as a cause of persistent morbidity after anterior cruciate ligament reconstruction. Med J DY Patil Univ 2015;8:785-7

How to cite this URL:
Kharat A, Garg S, Singh A, Kulkarni V. Magnetic resonance imaging of cyclops lesion as a cause of persistent morbidity after anterior cruciate ligament reconstruction. Med J DY Patil Univ [serial online] 2015 [cited 2022 Nov 28];8:785-7. Available from:

  Introduction Top

Cyclops lesion after anterior cruciate ligament (ACL) reconstructions has a reported incidence around 1-9.8%. [1] This occurs as a complication after arthroscopic treatment of ACL injury. It presents as a fibrous nodule in the intercondylar notch anterior to ACL graft. [2] The cyclops lesion resides in the anterior margin of the intercondylar notch, just above the tibial tunnel, which can become impinged between the tibia and femur upon knee extension. [3] It usually presents after 4-6 months of ACL grafting. Cylops lesion causes increased morbidity to the patient even after ACL reconstruction.

We present a case of cyclops lesion diagnosed by magnetic resonance imaging (MRI).

  Case Report Top

A 32-year-old male had undergone ACL reconstruction for knee instability 5 months ago. The patient presented with stiffness, pain and difficulty in extension. On physical examination, patient had difficulty to extend his left leg. There was no history of any chronic illnesses.

Magnetic resonance imaging was performed to diagnose the cause of stiffness and to evaluate ACL graft integrity, tunnel size and position or any meniscus injury. MRI of the left knee joint was performed without administration of intravenous contrast.

Magnetic resonance imaging revealed changes of ACL reconstruction. The ACL graft revealed edema-like signal. The graft was intact; however it appeared to be lax. There was marrow edema in the region of the tibial attachment of the graft [Figure 1]. A 1.8 cm × 1.0 cm diameter iso to hypo intense signal lesion was noted at the anterior aspect of the graft with patchy hyperintense foci within it, consistent with the diagnosis of a cyclops lesion [Figure 2]a-c. There was marked indentation by the anterior margin of the condylar notch on the superior surface of the graft. There was intermediate signal in the middle third of the graft. These features represented graft impingement.
Figure 1: MRI proton density fast spin echo sagital image of the knee. It reveals a marked edema in the graft shown by arrows with slackening of the graft. The anterior margin of the graft is not parallel to the Blumensat's line (line parallel to the roof of the intercondylar notch of the femur). There is an evidence of infl ammatory change and marrow edema at the tibial attachment of the graft

Click here to view
Figure 2: (a-c) MRI sagittal, coronal and axial proton density fast spin images of the knee with arrows pointing towards the cyclops lesion located anterior to the tibial attachment of the anterior cruciate ligament graft. The lesion is seen as hypointense with patchy central hyper intense foci within it on these images

Click here to view

The posterior cruciate ligament was normal. The medial and lateral collateral ligaments were normal. The popliteal muscle and tendon appeared normal. The quadriceps tendon and ligamentum patellae appeared normal. The Hoffa's fat pad was normal.

  Discussion Top

Localized anterior arthrofibrosis (cyclops lesion) is known to be the second most complication after ACL reconstruction. The first is graft impingement due to anterior placement of the tibial tunnel after ACL reconstruction causing extension loss of the knee. [4] Other reasons for loss of knee extension can be due to Hoffa's fat pad fibrosis, knee capsular contracture, suprapatellar or intercondylar adhesions, and patellar entrapment. [4]

This lesion was first described by Jackson and Shaffer in patients of ACL reconstruction as a condition presenting with loss of complete knee extension, audible and palpable "clunk" in terminal knee extension. [5] The term "cyclops" is derived from the Greek dictionary meaning a "three-eyed giant". It is also seen to be present in patients with ACL injury without a history of reconstructive surgery. Cyclops nodules have also been described in posttraumatic knee with a clinically and radiologically intact ACL. In such situations, it can be attributed to micro trauma leading to subclinically torn ACL bundles. [5]

The pathogenesis of the cyclops lesion is multifactorial. It is considered as a natural fibro proliferative reaction secondary to remnants after drilling, ACL stump tissue, torn graft fibers and impingement of the exposed fibers of the ACL on the intercondylar notch. [4],[6] It can also be a result of inadequate placement of the graft.

Histopathology of cyclops lesion shows that it contains central granulation tissue surrounded by adjacent dense fibrous tissue. The cyclops over a period, evolves from an early stage showing fibrosis to a late stage showing fibro cartilaginous dense, soft tissue. Cyclops may also contain fibrous tissue, fibrocartilagenous tissue, bone debris, synovium and fat from the infrapatellar fat pad. [7]

Magnetic resonance imaging is the primary post-operative investigative tool to evaluate failed ACL reconstruction, complications such as cyclops lesion, graft instability, disruption, extension loss, hardware fracture.

Magnetic resonance imaging is also a modality of choice for postoperative re-injury and pre-operative planning for repeat surgery. [8] MRI is found to be 85% sensitive, 84.6% specific and 84.8% accurate in diagnosis of cyclops lesion. [3]

Usually, cyclops nodule is found to be located in the intercondylar notch and always anterior to the ACL graft. The nodule gets pinched between the tibia and femur, these results in mechanical block to terminal extension. On MRI, the fibrous tissue signal characteristics are identified as lesion is hypo intense on T1-weighted images (T1WI) and T2-weighted images (T2WI) sequences. On T1WI, adjacent fluid may result in difficulty in diagnosing the cyclops lesion due to both showing low signal intensity. But T2WI, enables clear differentiation of cyclops lesion having a heterogenous low signal intensity, from joint fluid having high signal intensity. MRI arthrography, clearly outlines the lesion against the intra-articular contrast. [9]

On arthroscopy, the lesion has a head-like appearance with a focal area of reddish-blue discoloration due to venous channels that resemble an eye. Hence, it is called the "cyclops lesion." Aggressive physical therapy is not helpful in improving the extension loss. [10],[11] The treatment of choice is arthroscopic removal with additional notchoplasty if necessary. [4],[5],[9]

  Conclusion Top

Cyclops lesion should be considered as a possible cause of loss of extension after ACL reconstruction. Early definitive diagnosis with MRI and Arthroscopic excision acts as a definite treatment and provides a good patient outcome by reducing the morbidity of the patient.

  References Top

Pujol N, Colombet P, Potel JF, Cucurulo T, Graveleau N, Hulet C, et al. Anterior cruciate ligament reconstruction in partial tear: Selective anteromedial bundle reconstruction conserving the posterolateral remnant versus single-bundle anatomic ACL reconstruction: Preliminary 1-year results of a prospective randomized study. Orthop Traumatol Surg Res 2012;98:S171-7.  Back to cited text no. 1
Dhanda S, Sanghvi D, Pardiwala D. Case series: Cyclops lesion - Extension loss after ACL reconstruction. Indian J Radiol Imaging 2010;20:208-10.  Back to cited text no. 2
[PUBMED]  Medknow Journal  
Bradley DM, Bergman AG, Dillingham MF. MR imaging of cyclops lesions. AJR Am J Roentgenol 2000;174:719-26.  Back to cited text no. 3
Recht MP, Piraino DW, Cohen MA, Parker RD, Bergfeld JA. Localized anterior arthrofibrosis (cyclops lesion) after reconstruction of the anterior cruciate ligament: MR imaging findings. AJR Am J Roentgenol 1995;165:383-5.  Back to cited text no. 4
Runyan BR, Bancroft LW, Peterson JJ, Kransdorf MJ, Berquist TH, Ortiguera CJ. Cyclops lesions that occur in the absence of prior anterior ligament reconstruction. Radiographics 2007;27:e26.  Back to cited text no. 5
Sheldon PJ, Forrester DM, Learch TJ. Imaging of intraarticular masses. Radiographics 2005;25:105-19.  Back to cited text no. 6
Bradley DM, Bergman AG, Dillingham MF. MR imaging of cyclops lesions. AJR Am J Roentgenol 2000;174:719-26.  Back to cited text no. 7
Recht MP, Kramer J. MR imaging of the postoperative knee: A pictorial essay. Radiographics 2002;22:765-74.  Back to cited text no. 8
Recht MP, Piraino DW, Applegate G, Richmond BJ, Yu J, Parker RD, et al. Complications after anterior cruciate ligament reconstruction: Radiographic and MR findings. AJR Am J Roentgenol 1996;167:705-10.  Back to cited text no. 9
Shelbourne KD, Johnson GE. Outpatient surgical management of arthrofibrosis after anterior cruciate ligament surgery. Am J Sports Med 1994;22:192-7.  Back to cited text no. 10
Dodds JA, Keene JS, Graf BK, Lange RH. Results of knee manipulations after anterior cruciate ligament reconstructions. Am J Sports Med 1991;19:283-7.  Back to cited text no. 11


  [Figure 1], [Figure 2]


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

  In this article
Case Report
Article Figures

 Article Access Statistics
    PDF Downloaded186    
    Comments [Add]    

Recommend this journal