Two-slice-touch rule (knee MRI)

Dr Daniel J Bell ◉ and Dr Henry Knipe ◉ ◈ et al.

The two-slice-touch rule is a sign on MRI of the knee used to increase the sensitivity of diagnosing meniscal tears.

This rule states a meniscal tear is present if abnormal findings are present on two or more images - these do not have to be contiguous, e.g. can occur on sagittal and coronal slices but at the same anatomical location. The only exception to this rule applies to a meniscal root tear, for which abnormal signal in only one slice is considered highly specific for an underlying tear. A possible meniscal tear is present if abnormal findings are present on only one slice in other types of meniscal tear.

Quiz questions

{"accessible":false,"alternatives":[{"id":5556,"text":"it gives a PPV of above 90% for medial meniscal tear but less than 60% for lateral meniscal tear "},{"id":5557,"text":"it applies to horizontal and vertical longitudinal tears but not to radial tears"},{"id":5558,"text":"it was validated on 1.5 T MRI but is also thought to apply to 3.0 T MRI"},{"id":5559,"text":"the signal abnormality must be seen on two contiguous slices in the same plane"},{"id":5560,"text":"the signal abnormality must extend to the meniscal periphery"}],"archived":false,"correctAlternativeId":5558,"explanation":"\u003cp\u003eThe \u003ca title=\"Two-slice-touch rule (knee MRI)\" class=\"internal\" href=\"/articles/two-slice-touch-rule-knee-mri\"\u003etwo-slice-touch rule\u003c/a\u003e is satisfied if intra-meniscal high signal extends to the meniscal superior articular surface, inner free edge or inferior articular surface on at least two MRI slices. These two slices may be contiguous in the same plane, but can also be in different planes at the same anatomical location (eg. single sagittal slice and single coronal slice). Signal contacting the meniscal periphery does not form any part of the rule. \u003c/p\u003e\u003cp\u003eIt applies equally to radial tears just as it does to horizontal tears and vertical longitudinal tears. Radial root tears can often be reliably diagnosed on a single slice, and therefore the rule is not always applied to this small subset of radial tears.\u003c/p\u003e\u003cp\u003eIt was initially validated for 1.5 T MRI but is also thought to apply to 3.0 T MRI. It has a high PPV for both medial and lateral meniscal tears. The reported PPV values vary between studies however the medial meniscus tear PPV is consistently above 90% and the lateral meniscus tear PPV is often just as high, and is certainly nowhere near as low as 60%. \u003c/p\u003e","id":1112,"imageUrl":null,"nextQuestionPath":"/questions/1112/next","relatedArticles":[{"id":40036,"title":"Meniscal root tear","link":"/articles/meniscal-root-tear?lang=us"},{"id":39357,"title":"Longitudinal meniscal tear","link":"/articles/longitudinal-meniscal-tear?lang=us"},{"id":44003,"title":"Horizontal meniscal tear","link":"/articles/horizontal-meniscal-tear?lang=us"},{"id":41728,"title":"Radial meniscal tear","link":"/articles/radial-meniscal-tear?lang=us"},{"id":32943,"title":"Meniscal tear","link":"/articles/meniscal-tear?lang=us"}],"stem":"\u003cp\u003eWhich is true regarding the \"two-slice-touch\" rule for meniscal tear diagnosis on MRI?\u003c/p\u003e","articleId":"two-slice-touch-rule-knee-mri","nextQuestionId":null,"containerId":"expandableQuestionsContainer"}