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Musculoskeletal » Lower Extremity
Medial meniscal cyst and meniscal tear
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Author(s) :
Taco Geertsma, MD
Presentation 37 year old female patient with a palpable mass on the anterior medial aspect of the knee
Caption: Sagittal image of the mass on the medial aspect of the knee
Description: The mass is anechoic with septations consistent with a cystic lesion
Caption: Transverse image of the palpable mass on the medial aspect of the knee
Description: This transverse image shows a septated lesion in close contact to the medial femoral condyl
Caption: Sagittal image of the mass and the joint space with the anterior horn of the medial meniscus
Description: There is a close relation between the cyst and the base of the medial meniscus
Caption: Sagittal image of the mass on the medial aspect of the knee
Description: There is a faint anechoic line in the hyperechoic triangular medial meniscus, that can be followed to the cyst at the base of the meniscus. This line is a horizontal meniscal tear and the cyst is a meniscal cyst
Caption: Sagittal image of the joint space with the anterior horn of the medial meniscus
Description: The hyperechoic triangular medial meniscus shows an anechoic linear lesion consistent with a horizontal medial meniscal tear
Differential Diagnosis

Ultrasound is an excellent modality for examining the extra-articular structures. In case of a palpable mass ultrasound can differentiate between solid tumors and cystic lesions.

In a case of a fluid filled lesion the most likely diagnosis is


Fluid filled bursa

Liquefied hematoma

Final Diagnosis Medial meniscal cyst and meniscal tear

In case of a cyst, ultrasound in many cases can show a relation between the lesion and the different anatomical structures, as in this case the medial meniscus.

A meniscal cyst is usually associated with a miscal tear. Articular fluid is dispersed through the meniscal tear.

It is possible to do an ultrasound guided puncture of a meniscal cyst. Injection of corticosteroids can sometimes be helpful. Since the underlying cause is usually a pathological meniscus, it is better to treat the cause especially in younger patients

Another common fluid filled structure on the medial aspect of the knee is the pes anserinus bursa. In this case the typical location underneath the pes anserinus tendons makes it possible to differentiate it from a medial meniscal cyst.

In a case of a liquefied hematoma the patient history should be helpful

In case of a solid lesion, ultrasound is less reliable in determining the nature of the mass. Ultrasound however is helpful in performing guided punctures or biopsies

Although it is possible to detect meniscal tears with ultrasound, MRI is the modality of choice for examining the menisci and other intra-articular structures.
For more examples of meniscal cysts visit http://www.ultrasoundcases.info

Case References

Macmahon PJ, Brennan DD, Duke D, Forde S, Eustace SJ. Ultrasound-guided percutaneous drainage of meniscal cysts: preliminary clinical experience.Clin Radiol. 2007 Jul;62(7):683-7.

Rutten MJ, Collins JM, van Kampen A, Jager GJ. Meniscal cysts: detection with high-resolution sonography.AJR Am J Roentgenol. 1998 Aug;171(2):491-6.


Follow Up Patient had an athroscopy. The diagnosis was confirmed and a partial medial meniscectomy was performed
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