The Rising Moon sign is specific and sensitive in the diagnosis of bucket handle tears of the medial meniscus

Purpose: Bucket handle tears of the meniscus are common and can lead to locking, extension deficit and functional impairment. The diagnosis is determined by a combination of physical examination and imaging, but in some cases the diagnosis may be challenging since specific clinical tests are lacking. The aim of the present study was to assess the value of a new clinical test, the elective pain at the anterior aspect of the joint line (defined as the “Rising Moon sign”) in the diagnosis of bucket handle tears of the medial meniscus. Methods: Forty patients treated for a bucket handle of the medial meniscus were enrolled as the study group and were compared to a matched group of 40 patients with a posterior horn tear of the medial meniscus and 50 healthy subjects. The following aspects were investigated in the groups: body mass index, extension deficit, pain at the posterior aspect of the joint line (PPJL), at the middle joint line (PMJL), at the anterior join line (PAJL) and at combined hyperflexion of the knee and external rotation of the foot (PHE). Pain at the anterior joint line (PAJL) was defined as the Rising Moon sign. Results: In the bucket handle group the average flexion contracture was 12° (0–30°). The average PPJL was one (0–2), the average PMJL was 1.6 (0–3), PAJL was 2.5 (1–3) and PHE was 1.6 (1–2). In the posterior horn tear group the average flexion contracture was 0.9° (− 10 to 5°). The average PPJL was 2.2 (1–3), the average PMJL was 1.4 (0–3), PAJL was 0.6 (0–2) and PHE was 2.5 (1–3). The rising moon showed 95% sensitivity and 98% specificity in the diagnosis of bucket handle tears. In addition it showed a positive predictive value of 97.4% and negative predictive value of 96%. Finally it also demonstrated high inter-observer reliability (0.905). Conclusions: The “Rising Moon” sign has shown to be highly predictive for bucket handle tears of the medial meniscus with very high specificity and sensitivity. In addition it is easy to perform with very high inter-observer reliability. Level of evidence: Level IV.