title: Ring-shaped lateral meniscus with hypoplasic anterior cruciate ligament.
abstract: Knee joint lesions can be solitary or occur concomitantly with other lower limb abnormalities. Ring-shaped lateral meniscus (RSM) and hypoplasic anterior cruciate ligament (ACL) are two rare malformations. The therapeutic management of such abnormalities is not consensual, and highly depends on clinical symptomatology. We report a case of a 25-year-old girl with progressive knee pain whose MRI demonstrated a continuous segment of lateral meniscus situated along the medial aspect of the lateral compartment, continuous with the otherwise normal-appearing lateral meniscus, compatible with an RSM. This anatomic variant can be mistaken by a displaced meniscal fragment, like a bucket-handle tear, a central tear of a discoid meniscus, or incomplete discoid meniscus, as previously reported. Her MRI examination also showed a thinned ACL with anomalous lateral course. This abnormality may be mistaken for an ACL rupture and/or a meniscofemoral ligament with agenesis of ACL. Multiple images in different planes as well as following the course of meniscal and ligaments are critical clues to avoid misdiagnosis. As a result, the diagnosis of an RSM along with hypoplasic ACL with abnormal attachment was assumed based on MRI and confirmed during arthroscopy. The patient was treated conservatively with clinical outcome improvement.
authors.affiliation: Department of Radiology, Centro Hospitalar de São João, Alameda Prof. Hernâni Monteiro, 4200-319, Porto, Portugal. catiamcesteves@gmail.com.
authors.forename: Cátia
authors.initials: C
authors.lastname: Esteves
authors.affiliation: Department of Radiology, Centro Hospitalar de São João, Alameda Prof. Hernâni Monteiro, 4200-319, Porto, Portugal.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Castro
authors.affiliation: Department of Orthopedics, Centro Hospitalar de São João, Porto, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Cadilha
authors.affiliation: Department of Physical Medicine and Rehabilitation, Centro Hospitalar de São João, Porto, Portugal.
authors.forename: Frederico
authors.initials: F
authors.lastname: Raposo
authors.affiliation: Department of Radiology, Centro Hospitalar de São João, Alameda Prof. Hernâni Monteiro, 4200-319, Porto, Portugal.
authors.forename: Lina
authors.initials: L
authors.lastname: Melão
mesh_terms: D016118:Anterior Cruciate Ligament / Q000002:abnormalities* / Q000473:pathology*; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis* / Q000534:rehabilitation; D007719:Knee Joint / Q000002:abnormalities* / Q000473:pathology; D008592:Menisci, Tibial / Q000002:abnormalities* / Q000473:pathology*; D008875:Middle Aged; D016896:Treatment Outcome
keywords: Hypoplasic anterior cruciate ligament; Knee; Malformations; Ring-shaped meniscus