Medical Journal of Dr. D.Y. Patil Vidyapeeth

: 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

Amit Kharat, Sahil Garg, Amarjit Singh, Vilas Kulkarni 
 Department of Radiodiagnosis, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pune, India

Correspondence Address:
Amit Kharat
Flat 1101, C wing, Dew Drops Society, New Alandi Road, Vishranwatwadi, Pune - 411 015, Maharashtra


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.

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;8:785-787

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 2020 Nov 30 ];8:785-787
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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

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}{Figure 2}

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.


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]


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.


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