Background Baker’s cyst (BC) is synovial fluid accumulation in the gastrocnemius semimembranous bursa that communicates with the knee joint, often secondary to degenerative or inflammatory joint disease. Its breakdown usually produces swelling and pain of the affected lower limb, leading to loss of function. Normally, it does not require treatment unless it is symptomatic. In such cases, the cyst can be aspirated to reduce its size, with subsequent intra-articular administration of 40 mg triamcinolone acetonide to reduce inflammation. Synovectomy and intra-articular methotrexate (IAM) are reserved for refractory cases. However, in the bibliography review, we have only found two citations of IAM.

Purpose To describe the tolerability and effectiveness of IAM in the treatment of BC in a patient with rheumatoid arthritis (RA).

Material and methods A 54-year-old man with RA, treated with subcutaneous methotrexate 15 mg weekly and intravenous tocilizumab monthly,also presented with a relapsing cyst in the right lower limb aspirated on two previous occasions. In the presence of severe calf muscle damage, the patient was admitted to the hospital. Pig-tail drainage catheter was placed and washes with 20 ml of saline per nursing shift were made. After 3 days without improvement, interventional radiology service in cooperation with internal medicine contacted the hospital pharmacy requesting 25 mg methotrexate and 80 mg methylprednisolone for intra-articular administration. Via the interventional radiology service, precharged syringes of methotrexate and methylprednisolone were administrated by intra-articular injection through the catheter.

Results 2 months later, the patient’s disease was under control with an improvement in inflammatory markers: C reactive protein and erythrocyte sedimentation were 1 mg/mL and 12 mm/h, respectively, compared with 94 mg/L and 108 mm/h before methrotexate administration. 6 months later, he has not presented any signs of swelling and the inflammatory markers have remained <1 mg/L and 2 mm/h.

Conclusion Administration of IAM for the treatment of BC could be considered a well tolerated treatment option in recurrent and refractory cases to conventional treatment. Our patient presented analytical and subjective clinical improvement. However, more experience and follow-up are needed to draw conclusions to apply to clinical practice.

References and/or Acknowledgements See explanation to reviewers

No conflict of interest.