A case of intra-articular synovial lipoma of the knee joint causing patellar dislocation

Abstract

Intra-articular synovial lipoma is rare and clinically manifested mostly by mass effect and occasionally by torsion of the stalk. Patellar dislocation rarely occurs owing to a mass effect of intra-articular tumor of the knee joint. The authors present a case of large intra-articular synovial lipoma at the lateral gutter of the knee joint, which presents as patellar dislocation. A 19-year-old man visited our clinic due to pain and limitation of motion owing to mass at his left knee. MRI revealed an intra-articular soft tissue mass at the lateral gutter of the knee joint with considerable mass effect displacing patella from the trochlear groove. Excisional biopsy confirmed the diagnosis of lipoma, and the final diagnosis was intra-articular synovial lipoma with clinical information. The final radiograph showed well-aligned patella on the trochlear groove. After marginal excision, there was no recurrence or tumor-related morbidity.

A rare patella anatomical abnormality causing locking in an adolescent girl

“…The diagnosis was confirmed on a lateral radiograph, and the knee was easily unlocked under sedation with supero-lateral manipulation of the patella. Other rare causes of locking include intra-articular neoplasms, with reports of synovial lipoma [6,8] and pigmented villonodular synovitis [7,10]. A further rare and controversial presentation is that of the subluxing or dislocating intact meniscus.…”

“…The patella has been implicated in causing locking when superiorly dislocated, of which there have been less than 20 reported cases since 1956 [9]. Min et al also described patellar dislocation caused by a large lateral gutter lipoma in a 19‐year‐old male [8]. In addition, Goh et al [5] described locking in a teenage male caused by a loose osteochondral fragment as a result of a patella fracture sustained whilst dancing.…”

“…Other rare causes of locking include intra‐articular neoplasms, with reports of synovial lipoma [6, 8] and pigmented villonodular synovitis [7, 10]. A further rare and controversial presentation is that of the subluxing or dislocating intact meniscus.…”

“…Less common causes of locking include chondral or osteochondral lesions [5], ligamentous tears [3], and degenerative arthritides. Rare causes reported in the literature include the presence of gouty tophi [1, 2] or intra‐articular neoplasms such as a synovial lipoma [6, 8] or pigmented villonodular synovitis [7, 10].…”