Arthroscopic Decompression of a Popliteal Cyst

Abstract

Background:

Popliteal (Baker) cysts are enlarged gastrocnemius-semimembranosus bursae leading to swelling in the popliteal fossa. Surgical decompression and capsulectomy is the definitive treatment for symptomatic cysts with arthroscopic or open decompression. Arthroscopic decompression is minimally invasive, entails lower risks, and allows for earlier and more aggressive rehabilitation compared with open excision.

Indications:

Indications for popliteal cyst decompression include pain and mechanical discomfort refractory to conservative treatment. Further indications are neurovascular compromise secondary to bursal enlargement, including thrombophlebitis, compartment syndrome, limb ischemia, and nerve entrapment. Additional considerations include concurrent pathology requiring surgical intervention.

Technique Description:

Following standard diagnostic arthroscopy, a Gillquist maneuver is performed to visualize the posteromedial compartment and transverse synovial fold. The operative limb is placed in a modified figure-of-four position. A posteromedial portal is established under spinal needle localization and utilized to debride the anterior capsular wall and cyst contents with an arthroscopic shaver. Attention is paid to the removal of the posterior transverse synovial infold to reduce risk of recurrence.

Results:

The literature reports favorable outcomes in arthroscopic decompression of popliteal cysts. In comparison of arthroscopic and open decompression, You et al. reported reduced mean operative time and reduced recurrence rate following arthroscopic management. In a retrospective study, Rupp et al. reported increased rates of cyst recurrence with concurrent meniscal and/or chondral injuries highlighting the importance of addressing concurrent intra-articular pathologies during decompression.

Discussion/Conclusion:

Arthroscopic decompression of symptomatic popliteal cysts can be performed safely and effectively. Arthroscopic approach allows for treatment of concurrent pathologies that predispose to increased rates of cyst recurrence. Nonetheless, rates of recurrence vary widely and therefore further study in treatment technique is necessary.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

The following is a video presentation illustrating an arthroscopic decompression of a popliteal cyst, alternatively known as a Baker cyst.

We have no relevant disclosures and the authors’ full disclosures are available online.

In this video, we will provide a brief background on popliteal cysts, discuss a case presentation along with surgical pearls, describe our postoperative management, and review patient-reported outcomes.

Popliteal cysts, also known as Baker cysts, are the most common cystic pathology around the knee. A popliteal cyst frequently forms secondary to an intra-articular pathology, such as meniscus or cartilage injury. ¹ Excess synovial fluid created in response to degenerative wear or intra-articular trauma can lead to unidirectional flow of synovial fluid from the posterior intra-articular space into the gastrocnemius-semimembranosus bursa. Distention of this bursa leads to the symptomatic Baker cyst, which is maintained by a valve that prevents backflow of fluid into the articular space. While popliteal cysts are commonly found as incidental findings, larger cysts can cause posterior knee pain, stiffness, and swelling.

Initial treatment of popliteal cysts relies on nonoperative care, including oral antiinflammatories, corticosteroid injections, and needle aspiration. However, needle aspiration is associated with a high rate of recurrence. Some clinicians have advocated for targeted cyst aspiration with concomitant injection of either corticosteroid or platelet-rich plasma, however, this is not performed routinely in our practice. Patients with persistent symptoms >3 to 6 months in duration may be treated with either open or arthroscopic decompression. An arthroscopic technique affords a less invasive approach that can effectively address popliteal cysts, as well as concomitant pathologies within the knee. ²

In this case presentation, a 59-year-old otherwise healthy man presented to clinic following several weeks of right knee pain. His symptoms of pain and swelling occurred after performing leg extension exercises. His symptoms failed to abate with an intra-articular corticosteroid injection. He localized his pain to the posterior aspect of his knee and reported a visual analog scale (VAS) pain score of 6.

Physical examination of the right knee was notable for a 10-cc effusion, range of motion from 0 to 120° of knee flexion. The patient had tenderness along the posteromedial joint line, a positive McMurray test, and a stable ligamentous examination.

A standard series of knee radiographs was notable for marked chondrocalcinosis of both medial and lateral menisci, however, showed no evidence of advanced knee osteoarthritis.

Magnetic resonance imaging (MRI) of the right knee was remarkable for Grade 1 changes of the posterior horn of the medial meniscus along with a small, leaking Baker cyst. Mild cartilage wear is also appreciated in both medial and lateral compartments.

Indications for surgical management of symptomatic popliteal cysts include persistent symptoms refractory to nonoperative treatment, neurovascular compromise due to mass effect from a cyst, or concurrent pathology requiring surgical intervention. However, advanced degenerative changes within the knee is a relative contraindication to arthroscopic management. ⁷

Given the patient’s clinical history, examination, and imaging findings, the patient was indicated for right knee arthroscopic partial medial meniscectomy and a popliteal cyst decompression.

In the operating room, the patient was placed in the supine position and standard anterolateral and anteromedial arthroscopic portals were established.

In the medial compartment, a complex tear of the posterior horn of the medial meniscus with a horizontal cleft extending to the popliteal cyst was appreciated. The medial meniscus tear was debrided with a combination of an arthroscopic biter and shaver to leave a stable, smooth meniscal remnant as a final result.

Next, attention was turned to the popliteal cyst. A Gillquist maneuver was performed to visualize the posteromedial compartment. ³ Here, a rent on the transverse synovial fold, consistent with a Baker cyst, was visualized. Next, a posteromedial portal was established under spinal needle localization. Note that the operative limb is positioned in a modified figure-of-four position.

A blunt trocar is next inserted to dilate the capsular tissue to facilitate passage of an arthroscopic shaver. Via the posteromedial portal, the anterior capsular wall of the cyst was debrided, ⁴ and the cyst contents were decompressed with an arthroscopic shaver. Deliberate attention is made to remove the posterior transverse synovial infold, which can reduce the risk of recurrent cyst formation. The arthroscopic shaver carefully debrides all remnant cyst tissue and ensures that the remaining capsule is untethered.

Several complications may occur while performing this procedure. First, there may be difficulty gaining access to the cyst. To prevent this, positioning the operative knee in approximately 90° of flexion facilitates adequate space within the posterior compartment. Second, creation of a posteromedial portal just posterior to the medial femoral condyle affords the appropriate trajectory for a thorough arthroscopic shaver. Recurrence of the cyst is another complication. Removal of the posterior transverse synovial infold can reduce the risk of recurrent cyst formation. Finally, patients may report persistent knee pain following this procedure. It is essential to identify and treat concomitant intra-articular pathologies to reduce recurrent effusions that may predispose to popliteal cyst expansion.

Postoperatively, the patient was immobilized in a hinged knee brace locked in full extension and permitted to bear weight as tolerated. At 2 weeks postoperatively, the brace was unlocked, and physical therapy was initiated. The brace was discontinued at 6 weeks, and, at 3 months, the patient is permitted to begin jogging. Return to sport or full recreational activities generally occurs at 6 months.

At approximately, 3 months postoperatively, the patient’s knee pain had improved to a VAS pain score of 0 of 10 without swelling in the posterior aspect of the knee. At 6 months postoperatively, the patient’s pain score had remained at a 0 and he had improved 14 points as measured by the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement.

The available literature includes favorable outcomes associated with arthroscopic treatment of popliteal cysts. In one study comparing 27 arthroscopic cases against 75 open excision procedures, You et al ⁸ reported reduced mean operative time and reduced recurrence rates following arthroscopic management.

Similarly, in a retrospective analysis of 66 patients with a mean follow-up of 6.5 years, Rupp et al ⁵ reported increased rates of cyst recurrence in patients with meniscal and/or chondral injuries. These data highlight the importance of addressing concurrent intra-articular pathologies when treating symptomatic popliteal cysts.

In conclusion, arthroscopic decompression of symptomatic popliteal cysts can be performed safely and effectively. Arthroscopy allows for treatment of concurrent pathologies that may predispose to cyst recurrence. ⁶ Nonetheless, rates of recurrence vary widely, and therefore, further study in treatment techniques is necessary.

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