MR imaging of a meniscal ossicle

Abstract

We report the MR appearance of a meniscal ossicle, which is an unusual etiology for knee pain. The role of MR in differentiating a meniscal ossicle from a loose body is presented. The MR images also demonstrated associated tibial cartilage thinning and a possible meniscal tear. These MR findings led to arthroscopic treatment rather than conservative management. A review of the literature on meniscal ossicles is also presented.

Meniscal ossicle

“…MRI can easily depict the ossicles located inside the substance of the meniscus,[58] thus distinguishing them from loose bodies, chondrocalcinosis, osteochondritis dissecans, and semimembranosus and popliteal tendon avulsions. [5] Further, their characteristic isointensity to the adjacent normal bone marrow, along with the hypointense rim, also distinguish them from loose bodies and chondrocalcinosis, the latter appearing hypointense on T1W images.…”

Clinics in diagnostic imaging (144)

“…(2,3,5) Meniscal ossicles are defined as mature bone embedded within the substance of the meniscus. (5,6) Histologically, ossicles are seen as lamellar and cancellous bone with fatty bone marrow, and they are surrounded by meniscal fibrocartilage. (1,6,7) Several authors have reported foci of increased vascularisation, fibroblastic proliferation and even osteogenic activity.…”

“…(5,6) Histologically, ossicles are seen as lamellar and cancellous bone with fatty bone marrow, and they are surrounded by meniscal fibrocartilage. (1,6,7) Several authors have reported foci of increased vascularisation, fibroblastic proliferation and even osteogenic activity. (2) Patients either are asymptomatic or present with persistent or increasing knee pain, with reports of catching or clicking.…”

“…Associated meniscal tears have been reported and postulated as owing to alteration in the morphology of the meniscus. (5,6) The main differential diagnosis remains an intra-articular loose…”

“…One main theory postulates that they represent vestigial structures within the human knees, as meniscal ossicles are commonly seen in primates, cats and dogs. (6)(7)(8)(9) Another possibility is that they are post-traumatic sequelae, with metaplasia and heterotopic ossification within the meniscus occurring secondary to the trauma. (1,2,4) Finally, it has been proposed that meniscal ossicles occur following avulsion of the posterior horn of the meniscus with the detachment of a fragment of the posterior tibial margin (Fig.…”