Discoid meniscus

discoid meniscus

1. DISCOID MENISCUS Dr. Pratik Dhabalia Resident in Orthopedics Dr DY Patil Hospital, Navi Mumbai

2. ANATOMY MEDIAL MENISCUS C – shaped structure Most of the weight is borne by posterior part of meniscus LATERAL MENISCUS Semicircular More mobile than medial meniscus

3. BLOOD SUPPLY

4. EMBRYOLOGY The menisci differentiate from the mesenchymal tissue in the 8th week of gestation , and by week 14 they have their mature anatomical form.   Kaplan , did not identify discoid menisci as a stage during development and was the first to propose that the discoid form is due to a deficit in the posterior meniscofemoral fixation ( Wrisberg ). Although Kaplan’s theory does not explain the existence of discoid menisci with normal posterior femoral fixation, it is established that there is a synergy between discoid shape and instability. The meniscus is completely vascularized at birth, with progressive decline until age 10 years, at which point only the most peripheral third of the meniscus is vascularized. Discoid menisci have less vascularization in the periphery than those with normal shape.

5. ULTRASTRUCTURE Lower collagen density Disorganized network that predisposes it to breakage Histologically, the discoid meniscus presents mucinous alterations, similar to those found in degenerative menisci Thicker meniscus Increased surface area

6. DISCOID MENISCUS Abnormal development of meniscus leads to a hypertrophic and discoid shaped meniscus. Discoid meniscus is usually larger than normal Disc shaped

7. EPIDEMIOLOGY Incidence: Seen in 3-5% of population Predilection: Lateral meniscus is involved more frequently than medial 25% cases are bilateral

8. CLASSIFICATION - WATANABE

9. The posterior meniscal horn is fixed to the posterior cruciate ligament and the medial femoral condyle through the ligaments of Wrisberg (posterior meniscus-femoral ligament) and Humphrey (anterior meniscofemoral ligament). 1

10. PRESENTATION Usually asymptomatic unless they are unstable or torn Pain is most common Mechanical Clicking and locking Abnormal gait On Examination Lateral joint line pain Extension lag Clunk Positive meniscal tests

11. RADIOLOGY Radiographs of knee joint AP and lateral views Widened joint space Squaring of lateral femoral condyle Cupping of lateral tibia plateau hypoplastic intercondylar spine

12. MRI Confirming the diagnosis and preoperative planning Characterization of the meniscal shape, associated tears, stability, and concomitant injuries Discoid meniscus Transverse diameter >15mm in coronal view Continuity between anterior and posterior horns in three consecutive saggital cuts Ratio of minimal meniscus width to maximal tibial width >20% (sensitive and specific) BOW-TIE Sign

13. MRI Lateral discoid meniscus with a concomitant horizontal tear. Complete discoid meniscus with intrasubstance degenerative changes

14. MANAGEMENT Most patients are asymptomatic, since the knee eventually adapts to the anatomy, maintaining good function. Asymptomatic discoid meniscus without any tear – Observation and conservative management. Might get tear in near future so regular follow ups are required

15. Surgical treatment is recommended where there are persistent symptoms, such as pain, locking or limitation of sports activities. Given the known importance of the meniscus to knee function, and the fact that its absence triggers early degenerative changes, attempts to preserve the structure are an absolute priority

16. Surgical management Tears of complete or incomplete discoid menisci cause pain, popping, and snapping within the knee and that show a hypermobile medial segment but intact peripheral attachments are best treated by subtotal meniscectomy Saucerization of the mobile fragment

17. Wrisberg -type discoid meniscus lacks an adequate posterior tibial attachment Total meniscectomy, either open or arthroscopic subtotal meniscectomy alone leaves an unstable rim of meniscus that is certain to cause future problems

18. Rehabilitation Isolated discoid meniscus: Post Saucerization is to allow immediate total weight-bearing. Physical therapy is started after two weeks, with gradual return to sports after eight weeks. Meniscal repair: Partial weight-bearing with crutches, and a hinged brace with range of movement limited from 0º to 30º for the first six weeks. Full weight-bearing and progressive free range of movement is allowed at six weeks postoperatively. Physical therapy begins after two weeks postoperatively and return to sports depends on the patient’s movement and strength recovery, usually after 12 week