Medial Knee Osteoarthritis Precedes Medial Meniscal Posterior Root Tear with an Event of Painful Popping Dhong Won Lee, M.D, Ji Nam Kim, M.D., Jin Goo Kim, M.D., Ph.D. KonKuk University Medical Center
Dhong Won Lee, M.D, Ji Nam Kim, M.D., Jin Goo Kim, M.D., Ph.D. We have no financial conflicts to disclose.
Introduction Asian s lifestyle of squatting and sitting on the floor Impingement of the medial meniscal posterior horn Degenerative medial meniscal posterior root Prone to tear by minor trauma Degeneration change: Before Popping SI Bin et al. Arthroscopy 2004 Root elongation with MME > 3mm early OA (+)
Introduction Single event of painful popping during light activities Not only allows the physician to predict the presence of an MMPRT* but also predicts the degenerative status of the articular cartilage. * MMPRT: medial meniscal posterior root tear
Purpose & Hypothesis To assess magnetic resonance imaging (MRI) and radiologic findings of Medial Meniscal Posterior Root Tears (MMPRTs) with an event of painful popping within 3 weeks We hypothesized that most of MMPRTs with a single painful popping event would show pre-existed pathologic MME and articular cartilage degeneration, and larger contact area of medial femoral condyle to medial tibial plateau could affect the MME. In addition, MME would be correlated with knee osteoarthritis.
Patients and Methods Diagnostic cross-sectional study, Level IV. A total of 38 patients Inclusion criteria: 1) younger than 65 years old; 2) had a single event of painful popping; and 3) underwent MRI examinations within 3 weeks A painful popping was defined as a single episode of an explosive, sudden loud, painful sensation, and not a habitual clicking, and this event was occurred during walking, standing up or squatting, and going up or down stairs.
Patients and Methods Radiological assessments (x-ray) 1. Kellgren-Lawrence grade (Rosenberg view) Gr 1 - questionable osteophytes & no joint space narrowing Gr 2 - definitive osteophytes with possible joint space narrowing Gr 3 - definitive joint space narrowing with moderate multiple osteophytes Gr 4 - severe joint space narrowing with cysts, and sclerosis 2. Mechanical axis MRI Medial Meniscus extrusion (MME, mm) - Absolute MME and RPE (relative percentage of extrusion) Medial compartment cartilage loss evaluation : the modified Outerbridge scale (MOS) grade 1, cartilage surface fibrillation grade 2, <50% loss of cartilage thickness grade 3, >50% loss of cartilage thickness grade 4, exposed subchondral bone
Patients and Methods Articulation width of medial femoral condyle (MFC) at 0, 30, 60, and 90, medial tibial condyle (MTC) width, and MFC/MTC at 0, 30, 60, and 90 were measured. Larger medial femoral condyle (MFC) to medial tibial condyle (MTC) could affect the degree of MME. 0 30 60 90
Results Patient Demographic and Overall Results N =38 Age (yrs) 58.5 ± 10.5 Sex (male/female) 0/26 BMI (kg/m 2 ) 25.5 ± 2.7 Time from popping event to MRI examination (days) 15.4 ± 4.1 MME (mm) 2.9 ± 1.2 RPE (%) 22.0 ± 10.3 modified Outerbridge scale, 1 / 2 / 3 / 4 (n) 5 / 25 / 6 / 2 Kellgren-Lawrence grade, 1 / 2 / 3 / 4 (n) 6 / 30 / 2 / 0 Alignment Inv. (degree) 3.4 ± 2.6 Alignment Un-inv. (degree) 3.0 ± 2.2
Results Comparison of Overall Results between MME 3 mm MME < 3mm P value MME 3 mm and MME < 3 mm (Group G, n = 20) (Group L, n= 18) BMI (kg/m 2 ) 26.1 ± 2.8 25.3 ± 3.1 0.421 MME (mm) 3.8 ± 0.8 1.9 ± 0.6 < 0.001 RPE (%) 29.1 ± 9.2 14.5 ± 4.1 < 0.001 The ratio between MME and MFC/MTC at 0 4.2 ± 2.1 2.1 ± 0.7 < 0.001 modified Outerbridge scale, 1 / 2 / 3 / 4 (n) 1 / 12 / 5 / 2 4 / 13 / 1 / 0 0.035 Kellgren-Lawrence grade, 1 / 2 / 3 / 4 (n) 1/ 16 / 3 / 0 5 / 13 / 0 / 0 0.077 Alignment Inv. (degree) 3.6 ± 3.0 3.0 ± 2.3 0.545 Alignment Un-inv. (degree) 3.2 ± 2.5 2.7 ± 1.9 0.535 MFC/MTC at 0 0.90 ± 0.07 0.91 ± 0.03 0.322 MFC/MTC at 30 0.87 ± 0.05 0.88 ± 0.04 0.820 MFC/MTC at 60 0.92 ± 0.04 0.93 ± 0.05 0.462 MFC/MTC at 90 0.95 ± 0.06 0.93 ± 0.06 0.560
Results MME 3 mm MME < 3 mm P value Comparison of OA degree between (Group G, n = 20) (Group L, n= 18) MME 3 mm and MME < 3 mm Modified Outerbridge scale < Gr 3, n (%) Gr 3, n (%) 13 (65 %) 7 (35 %) 17 (94.4 %) 1 (5.6 %) 0.045 35% MOS Gr 3 K-L Gr Gr 3 Kellgren-Lawrence grade < Gr 3, n (%) Gr 3, n (%) 17 (85 %) 3 (15 %) 18 (100 %) 0 0.232 18% MME 3 mm 5.6% 0 MME < 3 mm Correlation between Medial Meniscal Extrusion (MME) Parameters and modified Outerbridge Scale, and Kellgren-Lawrence Grade modified Outerbridge scale Kellgren-Lawrence grade MME 0.522** 0.579** RPE 0.485* 0.504** Ratio between MME and MFC/MTC at 0 0.525** 0.576** * < 0.05, ** < 0.001. MME, Medial meniscal extrusion; RPE, Relative percentage of extrusion; MFC, Medial femoral condyle; MTC, Medial tibial condyle.
Conclusion Potential strength of the present study include the identification of medial compartment degenerative condition at the time of a painful popping in MMPRTs and evaluation of correlation between MME parameters and MOS, K-L grade, and regional knee geometry. More than 80% of MMPRT patients with an event of painful popping within 3 weeks showed that medial compartment degeneration preceded the event of popping. Therefore, identification of MME and articular cartilage degeneration at the time of painful popping in MMPRTs could be helpful when the surgeon determines the most appropriate treatment.
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