A popliteal cyst, also referred to as a Baker's cyst, is among the most common cystic lesions encountered around the knee joint in orthopedic practice, resulting from distension of the gastrocnemius-semimembranosus bursa within the popliteal fossa and is typically filled with synovial fluid. Magnetic resonance imaging (MRI) is widely used to detect and characterize these cysts. Various invasive and non-invasive therapeutic strategies have been described for the management of Baker's cysts. This review summarizes the clinical presentation, diagnostic evaluation, and current management approaches for popliteal cysts.

Cystic adventitial disease is a rare, nonatherosclerotic condition most commonly affecting the popliteal artery in the popliteal fossa. We describe the case of a 44-year-old man with episodic calf claudication in whom duplex ultrasound and computed tomography angiography showed cystic lesions surrounding the popliteal artery with mild luminal narrowing, consistent with cystic adventitial disease. Conventional magnetic resonance (MR) imaging identified a popliteal artery adventitial cyst with suspected knee joint connection. Fluoroscopically guided intra-articular gadolinium injection in the knee followed by 3-T MR arthrography confirmed cyst communication with the knee joint. This case supports the articular theory and highlights MR arthrography as a problem-solving tool in selected cases.

Popliteal artery aneurysms (PAA) lose their pulsatility once thrombosed and may therefore be mistaken for a Baker cyst or a soft-tissue tumor. A 58-year-old male presented with a 6-month history of progressive right popliteal swelling and pain, accompanied by right foot paresthesia and diminished distal pulses for two months. The presence of accompanying neurovascular deficits shifted the diagnostic consideration from a benign soft-tissue lesion to a vascular disorder. In this patient, non-contrast imaging protocol integrating grayscale ultrasound, power Doppler, and magnetic resonance imaging (MRI) successfully identified a chronically thrombosed popliteal artery aneurysm, supporting a vascular rather than neoplastic etiology. While ultrasound cannot replace contrast-enhanced MRI for definitive tissue characterization, its real-time capability established a vascular etiology and guided subsequent diagnostic digital subtraction angiography with urgent endovascular stent-graft reconstruction. Furthermore, serial ultrasonographic surveillance at three and 18 months confirmed long-term stent-graft patency and favorable aneurysmal sac remodeling. Neurovascular deficits accompanying a popliteal mass should redirect the workup toward vascular imaging. This case underscores a critical diagnostic pitfall, demonstrating that a stepwise strategy combining real-time ultrasound and non-contrast MRI ensures rapid definitive management for complex popliteal masses while preserving the unique role of sonography in non-invasive follow-up.

A 60-year-old male patient presented to the vascular clinic with a three-month history of a large popliteal fossa swelling post Baker's Cyst Aspiration. This swelling had been getting progressively larger over this period. CT angiogram of his lower limb reported a right popliteal aneurysm of 8.5 cm diameter with a large amount of intramural thrombus that was later confirmed as a pseudoaneurysm in our vascular multi-discliplinary meeting. It was decided to dissect the popliteal artery from a posterior approach and perform a bypass using a vein. Intraoperatively, a biological bovine pericardial patch was used for repair of his pseudoaneurysm. Postoperatively the patient was well from both a surgical point of view and suffered mild symptoms of COVID-19. Open surgery with primary repair with bovine pericardial patch demonstrated an alternative to treat this condition.

PurposeTo evaluate structural factors associated with Baker's cyst volume and determine whether cyst enlargement is related to medial meniscus posterior root tear (MMPRT), medial meniscus extrusion (MME), posterior tibial slope (PTS), and radiographic osteoarthritis severity.MethodsThis retrospective study included 876 knee MRI examinations with MRI-confirmed Baker's cysts after predefined exclusions. Baker's cyst volume, MMPRT status, MME, PTS, and Kellgren-Lawrence osteoarthritis grade were assessed using standardized imaging protocols. Factors associated with cyst volume were evaluated using multivariable linear regression. Logistic regression and receiver operating characteristic analysis were performed to assess the relationship between cyst volume and MMPRT. Measurement reliability was evaluated using intraclass correlation coefficients.ResultsMMPRT was independently associated with larger Baker's cyst volume (p = 0.004). Greater PTS was also associated with increased cyst volume, with each 1° increase corresponding to a significant volume increase (p = 0.012). Increasing Kellgren-Lawrence grade remained independently associated with larger cyst volume (p < 0.001), and MME showed an independent but modest association (p = 0.044). The final regression model was significant (F (8,867) = 23.45, p < 0.001) and explained 17.8% of the variance. ROC analysis identified 10.16 cm[3] as the optimal cyst volume threshold for identifying MMPRT; however, discriminative performance was modest, indicating that cyst volume should not be interpreted as a standalone diagnostic marker. ICC values ranged from 0.79 to 0.91.ConclusionBaker's cyst enlargement is associated with MMPRT, increased PTS, greater MME, and increasing osteoarthritis severity. Larger cysts may prompt careful evaluation of the medial meniscus posterior root and degenerative joint burden on routine knee MRI, but cyst volume should be interpreted together with other structural imaging findings.