Infected Baker's Cyst: A New Classification, Diagnosis and Treatment Recommendations

Abstract

Introduction: Baker's cyst has a high prevalence in adult population. Despite being usually asymptomatic, cyst complications may develop, such as an infection, rupture and content dissemination into the calf. This clinical presentation has a low incidence with few reports in the literature. We have not found any publication describing a systematic approach for its treatment. The purpose of this study is to propose a new classification, diagnosis, and treatment recommendations based on a case report and a literature review to guide physicians on the best course of treatment.

Case report: A 53-year-old man presented with sudden left popliteal pain associated with progressive knee and calf swelling and limited knee flexion. After the initial evaluation, a Baker's cyst rupture and dissemination into the calf, associated with a septic arthritis, were diagnosed. An arthroscopic surgical irrigation of the knee and open debridement of the calf collection were performed.

Conclusion: Our classification may allow an accurate and structured description of the different stages of Baker's cyst presentations, with simplification of the clinical description, diagnosis, and treatment approaches.

Keywords: Baker’s cyst; Diagnosis algorithms; Knee infection; Septic arthritis; Treatment algorithms.

Figure 1

(a) Clinical presentation of a 53-year-old man left leg. Notice the swelling in the medial and proximal aspects of the leg. (b) Left calf musculoskeletal ultrasound showing an hypoechogenic image (15 cm × 3 cm). (c) Left calf magnetic resonance imaging. Baker’s cyst rupture with content dissemination to the calf muscles.

Figure 2

Intraoperative images: Posteromedial, longitudinal approach in the middle third of the calf.

Figure 3

Graphics showing the possible valvular mechanisms: Intra-articular loose bodies (a) and pedicle bending (b).

Figure 4

Schematic diagram of the technique proposed for an intact cyst drainage. Notice the Abbocath left in the cyst allows fluid to drain from the cyst during articular irrigation.