A 22-year-old female presented with pain and swelling on the lateral aspect of the left knee since two weeks, associated with restriction of movements. She had a history of fall and trauma to the left knee three years back. She had no history of fever. On examination, a palpable swelling with localized tenderness was present. An ultrasound examination performed previously in another institution had revealed a cystic lesion in the lateral aspect of the knee joint which was thought to be a ganglion cyst.
A non- contrast MRI (Magnetic Resonance Imaging) of the knee was performed. Anterior cruciate ligament (ACL) was thickened with diffuse high signal intensity on all the sequences, suggesting mucoid degeneration. Medial meniscus, posterior cruciate ligament, medial and lateral collateral ligaments appeared normal. The lateral meniscus showed a bucket handle tear with a medially flipped fragment. A well-defined, cystic lesion measuring 36x29x19mm was seen arising from the anterior horn of the lateral meniscus. It showed thin internal septae and smooth margins. It was seen to bulge into the Hoffa’s fat pad anteriorly with mild scalloping of the underlying anterior tibial cortex. A small cyst was seen adjacent to the posterior body of the lateral meniscus.
All bones showed normal marrow signal intensity. There was no joint effusion. The patient was referred to a higher institution for surgical management of the large parameniscal cyst.
Knowledge of anatomy is vital to classify the cystic and ‘cyst-like’ lesions when imaging a post-traumatic knee. These lesions include- popliteal cysts, ganglion cysts, synovial cysts, meniscal cysts and intraosseous cysts while the cyst-like lesions include fluid-filled bursae and recesses which may mimic cysts. Causes other than trauma include osteoarthritis, rheumatoid arthritis, gout and systemic lupus erythematosus. A parameniscal cyst is a well-defined fluid collection seen adjacent to a meniscus. They may show lobulations, internal septations and rarely bony erosions. Intrameniscal cysts are seen within the meniscus. [1] Ultrasonography, CT, arthrography and MRI are the various imaging techniques used in their evaluation. MRI is most preferred modality as it is non-invasive, does not use ionizing radiation and has superior soft-tissue contrast resolution. [2]
Ganglion cysts may be extra-articular, intraarticular, periosteal or intraosseous but are not associated with meniscal tears. The first type is commonest and presents as a cystic mass surrounded by dense connective tissue without a synovial lining. Meniscal cysts are associated with horizontal meniscal tears. It is believed that they are formed due to extrusion of synovial fluid through an adjacent meniscal tear. [3] Synovial cysts can be distinguished from other juxta-articular lesions by their synovial lining. [4] Most common examples are Baker’s cyst and proximal tibiofibular joint synovial cyst. Cysts in the extremities are usually asymptomatic but pain or discomfort may arise from inflammatory changes, rupture, haemorrhage or infection. Malignancy needs to be ruled out in complex cysts with associated soft tissue mass.
Surgical excision, aspiration and steroid injections are treatment options, however, recurrence rates are high when managed conservatively. [5]
Parameniscal cyst associated with bucket handle tear
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Based on the provided knee MRI images, a well-defined cystic abnormal signal is observed in the lateral aspect of the left knee joint (near the lateral meniscus). On T2-weighted images, this cystic lesion appears as a high signal with a relatively regular shape, closely adjacent to the edge of the meniscus. There is no obvious soft tissue or bony destruction. A faint signal abnormality is suspiciously visible at the inner margin of the meniscus, suggesting a possible mild meniscal tear or fissure.
The overall cartilage outline is still acceptable, and there is no significant destruction or obvious bone marrow edema within the femoral condyles or the tibial plateau. No extensive edema is seen in the surrounding soft tissue, but a small amount of inflammatory change is noted locally.
Considering the patient’s history of injury (a fall 3 years ago), local symptoms (lateral knee pain, restricted movement), and the current MRI findings, the most likely diagnosis is: Mild Tear of the Lateral Meniscus of the Left Knee with a Parameniscal Cyst.
This condition is commonly associated with the extravasation of joint fluid through a horizontal or oblique meniscal tear, forming a cystic lesion around the meniscus, which correlates with the ultrasound report describing a “cystic lesion.”
Rehabilitation training should follow a gradual and individualized approach. A possible plan is as follows:
During this process, if the patient’s bone quality is relatively fragile or there are other potential health issues (such as cardiopulmonary disorders), appropriate medical evaluations should be conducted to ensure safety and control in the chosen exercise regimen.
This report is based solely on the provided information for a preliminary analysis and is intended as a reference for patients and clinical physicians. Specific diagnosis and treatment should be determined in combination with further examinations and in-person consultations. It does not replace a professional doctor’s face-to-face diagnosis and treatment advice.
Parameniscal cyst associated with bucket handle tear
