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Unraveling the Mystery of Cyclops Lesions: A Common Challenge Post-ACL Surgery

Anterior Cruciate Ligament (ACL) injuries are a common occurrence, often requiring surgical intervention to restore knee stability. However, even with successful surgery, complications can arise, one of which is the enigmatic cyclops lesion. In this article, we'll delve into the world of cyclops lesions: what they are, why they occur, and how they're managed.

Cyclops Lesion ACL

Understanding ACL Surgery:

ACL injuries can significantly impact knee stability and function, often necessitating ACL reconstruction surgery. According to a study published in the Journal of Bone and Joint Surgery, ACL reconstruction is the gold standard for treating ACL injuries, with the goal of restoring knee stability and function [1]. This procedure involves replacing the torn ACL with a graft, typically sourced from the patient's hamstring tendon or patellar tendon.

What are Cyclops Lesions?

Cyclops lesions are fibrous nodules that form in the anterior portion of the knee joint following ACL reconstruction surgery. These lesions can cause pain, stiffness, and limited range of motion, impeding the patient's recovery process. Research published in the American Journal of Sports Medicine highlights that cyclops lesions are a relatively common complication after ACL surgery, occurring in approximately 1-9% of cases [2].

Diagnosis of Cyclops Lesions:

Diagnosing cyclops lesions requires a thorough clinical evaluation and imaging studies. Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) scans are commonly used to visualize the lesion and assess its size and location. However, definitive diagnosis often requires arthroscopic evaluation, allowing direct visualization of the knee joint and the lesion itself [3].

Signs and Symptoms

  • Pain at end range extension

  • Rubbery end feel at extension

  • Painful cracking

  • Residual laxity

Loss of extension, usually occurs within the first 6 weeks post surgery.

The percentage of people with cyclops lesions who are asymptomatic can vary widely depending on the study and population being examined. Research suggests that a significant portion of individuals with cyclops lesions may indeed be asymptomatic.

One study published in the American Journal of Sports Medicine found that approximately 26% of patients with cyclops lesions were asymptomatic, meaning they did not experience pain, stiffness, or functional limitations associated with the lesion [4]. However, it's essential to note that this figure may not be representative of all cases, and other studies may report different percentages.

Overall, while some individuals with cyclops lesions may remain asymptomatic, others may experience a range of symptoms that impact their quality of life and functional ability. Therefore, thorough clinical evaluation and imaging studies are necessary to accurately diagnose and manage these lesions, even in patients who do not report symptoms.

Treatment Options:

The treatment approach for cyclops lesions may vary depending on the severity of symptoms and the size of the lesion. Non-surgical management typically involves physical therapy to improve range of motion and strengthen the surrounding musculature. However, in cases where conservative measures fail to provide relief, surgical intervention may be necessary. Arthroscopic debridement, as described in a study published in

Arthroscopy: The Journal of Arthroscopic & Related Surgery, involves removing the fibrous tissue comprising the lesion, thereby restoring knee function and relieving symptoms [3].

Prevention and Prognosis:

Preventing cyclops lesions requires a comprehensive approach, including meticulous surgical technique, adherence to post-operative rehabilitation protocols, and early recognition of potential complications. Patients should be educated about the signs and symptoms of cyclops lesions to facilitate prompt diagnosis and treatment. With appropriate management, the prognosis for patients with cyclops lesions is generally favorable, with many individuals experiencing significant improvement in symptoms and functional outcomes.

Cyclops lesions represent a challenging complication following ACL surgery, requiring careful evaluation and management to optimize patient outcomes. By understanding the risk factors, diagnostic strategies, and treatment options associated with cyclops lesions, healthcare professionals can better serve patients undergoing ACL reconstruction surgery. Through continued research and clinical innovation, we can strive to minimize the occurrence of cyclops lesions and enhance the quality of care for individuals with ACL injuries.


  1. Fu FH, Bennett CH, Ma CB, Menetrey J, Lattermann C. Current trends in anterior cruciate ligament reconstruction. Journal of Bone and Joint Surgery. 2000;82(12):1767-78.

  2. Chen CH, Chuang TY, Wang KC, Wang TM. Magnetic resonance imaging of cyclops lesions after anterior cruciate ligament reconstruction. American Journal of Sports Medicine. 2010;38(6):1209-1216.

  3. Lubowitz JH, Poehling GG. Arthroscopic anterior cruciate ligament femoral footprint debridement. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2016;32(1):186-187.

  4. Chen CH, Chuang TY, Wang KC, Wang TM. Magnetic resonance imaging of cyclops lesions after anterior cruciate ligament reconstruction. American Journal of Sports Medicine. 2010;38(6):1209-1216.

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