Kinematic Analysis of Lateral Meniscal Oblique Radial Tears in Anterior Cruciate Ligament–Reconstructed Knees: Untreated Versus Repair Versus Partial Meniscectomy

Background: Lateral meniscal oblique radial tears (LMORTs) affect joint and meniscal stability in anterior cruciate ligament (ACL)–deficient knees. Purpose: To determine the clinically relevant kinematics associated with the most common posterior horn LMORT lesion types, types 3 (LMORT3) and 4 (LMORT4), untreated versus arthroscopic repair versus partial meniscectomy in combination with ACL reconstruction (ACLR). Study: Controlled laboratory study. Methods: Sixteen cadaveric knees underwent robotic testing for anterior drawer and pivot-shift simulations at multiple knee flexion angles in ACL-intact and ACL-deficient states, followed by sequential testing of arthroscopic ACLR, LMORT3 lesion, LMORT3 repair, and partial meniscectomy (n = 8). The same testing sequence was performed for LMORT4 lesions (n = 8). Results: ACLR restored kinematics in ACL-deficient knees to intact levels for all metrics tested. For anterior drawer, ACLR + LMORT3 tear and partial meniscectomy resulted in significantly greater anterior translation compared with ACL-intact at all angles (P <.05) and compared with ACLR at 60° and 90° (P <.014). For pivot shift, compared with ACL-intact knees, ACLR + LMORT3 tear resulted in significantly more anterior translation at 15° (P =.041); and for ACLR + partial meniscectomy, at both 0° and 15° (P <.03). ACLR + LMORT4 tear and partial meniscectomy resulted in significantly greater anterior translation for anterior drawer (P <.04) and pivot-shift testing (P <.05) compared with intact and ACLR knees at all angles tested. ACLR + LMORT3 repair and ACLR + LMORT4 repair restored kinematics to ACLR and intact levels at all angles tested. ACLR + LMORT3 tear (P <.008) and both LMORT4 tear and partial meniscectomy (P <.05) resulted in increased meniscal extrusion compared with intact and ACLR statuses at all tested angles for anterior drawer and pivot shift, while repairs restored meniscal stability to ACLR and intact levels. Conclusion: Untreated LMORT tears increased anterior translation, pivot shift, and meniscal extrusion after ACLR, while partial meniscectomy further exacerbated these detrimental effects in this cadaveric model. In contrast, arthroscopic side-to-side repair of LMORT lesions effectively restored measured knee kinematics. Clinical Relevance: LMORT lesions are common with ACL tears and adversely affect joint stability and meniscal extrusion. This study highlights the importance of repair of LMORT 3 and 4 lesions at the time of ACLR.