The occurrence of intra-articular ganglions in patients referred for knee examination is rare (1.3%),~( 3 )and previous studies have demonstrated that the most common cysts are located in the anterior cruciate ligament (ACL) (62.6% to 75.4%).~( 7 , 8 )While its etiology is unclear, some authors affirm that cysts appear after a trauma and others advocate for an origin of cystic degeneration within the ligament.~( 11 , 13 )The presence of these intra-articular cysts can occasionally become symptomatic, causing pain and limiting activities.~( 8 , 12 , 15 ) The diagnosis of an intra-articular ganglion cyst can be clearly made by magnetic resonance imaging (MRI).~( 4 , 6 )Currently, arthroscopic resection of the cyst is the most common method of treatment for symptomatic cysts.~( 2 )Arthroscopic debridement for this condition could lead to complications, such as iatrogenic injury to the ACL.~( 3 , 13 )To hasten the improvement of symptoms and return to play, we proposed an alternative treatment option with the use of computed tomography (CT)–guided aspiration of the ACL ganglion cyst, a previously described technique with clinical success.~( 1 ) The purpose of this study was to report results in a professional athlete with both 2-year clinical and MRI follow-up. Institutional review board approval was obtained for this study. Case Presentation A 25-year-old international professional soccer player was evaluated in our clinic for atraumatic, isolated knee pain and significant limitation of knee flexion at the conclusion of the 2012-2013 professional soccer season. The patient complained of a vague pain in the right knee, initially occurring for about 1 month, that did not result in any lost playing time or medical treatment. Thereafter, the patient experienced a sudden limitation of range of motion (ROM). Clinical examination revealed pain with terminal flexion and a flexion loss of 15°. Stability tests, including Lachman, anterior and posterior drawers, pivot shift, and valgus and varus stress, were all negative. A rolimeter demonstrated a side-to-side difference of 2 mm compared with the contralateral knee. An MRI was completed, which subsequently revealed an ACL ganglion cyst with an anterior-posterior dimension of 16.6 mm ( Figure 1 ). Figure 1. MRI showing ACL ganglion cyst. (A) Sagittal, (B) coronal, and (C) axial views. The patient was scheduled to participate in the upcoming World Cup in June 2014, and arthroscopic debridement might not have allowed for a full return to sport prior to the beginning of the games. The decision was subsequently made to perform a CT-guided aspiration instead to facilitate rapid recovery and return to sport. A radiologist performed the procedure under CT scan control using a posterior-lateral approach without anesthesia. Aspiration of the cyst was performed using a 22-gauge needle, followed by injection of corticosteroid (Cortivazol 3.75 mg, 1.5 mL) into the lesion ( Figure 2 ). Figure 2. (A) Identification of the ACL ganglion cyst measuring 16.6 mm. (B) Aspiration of the cyst by a 22-gauge needle through posterolateral approach. The procedure resulted in instantaneous relief of the patient’s pain and ROM limitation. The professional soccer player was able to return to training 1 week later and was able to play at the World Cup without pain or limitation. Twenty-four months later, he is still asymptomatic during all sports and daily activities. An MRI of the same knee was obtained secondary to an unrelated medial collateral ligament (MCL) injury that occurred during a game. The MRI shows the continued presence of the ganglion cyst but with a significant reduction in its size (anterior-posterior dimension of 5.4 mm) ( Figure 3 ). Physical examination at last follow-up demonstrated pain-free ROM of the knee, continued stability with ligamentous testing, and the same 2-mm side-to-side difference in rolimeter testing. Figure 3. Two-year follow-up MRI showing ACL ganglion cyst with a significant reduction in size (anteroposterior dimension, 5.4 mm). (A) Sagittal, (B) coronal, and (C) axial views. Discussion Ganglion cysts associated with knee cruciate ligaments are uncommon and usually occur in the ACL, with a prevalence of 1.3% in a group of 1767 consecutive patients referred for MRI examinations of the knee and 0.6% after arthroscopy.~( 8 , 11 , 12 )The etiology of these ganglion cysts is unknown. Despite many reports of ganglia developing in the absence of trauma, it is believed that repetitive microtrauma from joint and soft tissue motion causes expansion of both mucin and hyaluronic acid from ligament fibers, thus acting as a potential trigger.~( 3 )Others advocate for an origin of cystic degeneration within the ligament itself, with subsequent mucoid degeneration and ganglion cyst formation, a similar pathogeneses as in intraosseous cyst formation.~( 11 , 13 ) Most cysts are asymptomatic, but in some cases they can be a significant source of pain and discomfort.~( 3 , 9 )Fre
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