The Biomechanical Effect of a Lateral Meniscus Posterior Root Tear With and Without Damage to the Meniscofemoral Ligament: Efficacy of Different Repair Techniques Philipp Forkel, M.D., Mirco Herbort, M.D., Frederike Sprenker, Cand. Med., Sebastian Metzlaff, M.D., Michael Raschke, Ph.D., and Wolf Petersen, Ph.D. Purpose: To evaluate the effect of the meniscofemoral ligament (MFL) in maintaining lateral-compartment contact pressures after injury to the posterior root of the lateral meniscus, and to measure the ability to restore intra-articular loads to normal by repairing the posterior root to the tibia after transection of the posterior root and the MFL. Methods: Ten human cadaveric knee joints were axially loaded to 100 N. A digital pressure sensor measured the contact pressure in the lateral compartment. Five different conditions were tested: intact, after release of the posterior root of the lateral meniscus, after transection of the MFL along with release of the posterior root, refixation of the posterior root of the lateral meniscus to the tibia using an anatomic transosseous tunnel, and refixation of the root of the lateral meniscus using a tibial anterior cruciate ligament (ACL) tunnel. Results: After transection of the posterior lateral meniscus root, the contact pressure did not increase significantly. The additional transection of the MFL led to a significant increase in the contact pressure. Anatomic fixation of the meniscus posterior horn reduced the femorotibial pressure to nearly pre-sectioning values. The reattachment of the meniscus posterior horn through a tibial ACL tunnel was equivalent to an anatomic fixation. Conclusions: In the case of a root tear of the lateral meniscus, the MFL maintains meniscus function and stabilizes the pressure in the lateral compartment. A complete detachment of the posterior meniscus horn (MFL and root tear) leads to an increase in the intra-articular pressure. A root repair normalizes the pressure down to normal values. The tibial ACL tunnel is suitable to perform the repair and to lead out the suture. Clinical Relevance: In the case of a complete detachment of the meniscus posterior horn, fixation of the posterior root is necessary to restore the meniscus function and to guarantee an equal pressure distribution in the lateral compartment. It can be combined with an ACL reconstruction. T he knee joint menisci increase femorotibial con- gruency, and they contribute significantly to load transmission and joint stability. During load trans- mission, the forces acting on the meniscus are trans- formed into circumferential hoop stress. 1 This circular hoop stress is transmitted to the tibial plateau by the anterior and posterior roots of the menisci. 1 Therefore the posterior horn attachments of the menisci are essential in maintaining the mechanical function of the menisci. The anatomy of the lateral meniscus posterior attachment differs from the anatomy of the medial meniscus. In addition to the tibial attachments, the posterior horn of the lateral meniscus is connected to the intercondylar area of the femur by the meniscofe- moral ligaments (MFLs). 2 The MFLs show a high vari- ation of the femoral insertion site. 3 The Wrisberg ligament (posterior MFL) and the Humphrey ligament (anterior MFL) typically insert at the medial femoral condyle. An attachment to the PCL is also common. 3 The posterior MFL is difficult to assess arthroscopi- cally, although we know of its high prevalence of up to 69% from cadaveric studies. 4 The function of the MFL as a secondary restraint to posterior drawer is well known. 5 Amadi et al. 6 showed that a single transection of the MFL leads to an increase in the intra-articular pressure. However, the capability of the MFL to prevent the loss of meniscus function in the case of a root tear is debated controversially and From the Klinik für Orthopädie und Unfallchirurgie, Martin-Luther- Krankenhaus (P.F., F.S., S.M., W.P.), Berlin; and Klinik für Unfall-, Hand- und Wiederherstellungschirurgie, Universitätsklinikum Münster (M.H., M.R.), Münster, Germany. The authors report the following potential conflict of interest or source of funding: The study was supported by the Gesellschaft für Arthroskopie und Gelenkchirurgie. M.H. receives support from Karl Storz. W.P. receives support from Karl Storz, Otto Bock. Received May 29, 2013; accepted February 27, 2014. Address correspondence to Philipp Forkel, M.D., Klinik für Orthopädie und Unfallchirurgie, Martin-Luther-Krankenhaus, Caspar-Theyß-Strasse 27-31, Berlin, Germany. E-mail: ph.forkel@gmail.com Ó 2014 by the Arthroscopy Association of North America 0749-8063/13350/$36.00 http://dx.doi.org/10.1016/j.arthro.2014.02.040 Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 30, No 7 (July), 2014: pp 833-840 833