We will present a rare case of a large symptomatic cyst of the medial meniscus, conjoined with a horizontal tear of a posterior meniscal horn. After clinical, radiological and ultrasound examination, a diagnosis was confirmed with MRI examination of the knee. Literature supports surgical therapy, which includes complete arthroscopic technique, meniscectomy and decompression of the cyst. In our case, it showed that arthroscopic partial meniscectomy and opened cystectomy were the efficient way of treatment.