Anterior meniscus extrusion is associated with anterior tibial osteophyte width in knee osteoarthritis - The Bunkyo Health Study

Changes in the position of the medial meniscus owing to degenerative meniscus tears

Background

While meniscal extrusion has been recognized as a key factor in meniscal dysfunction and osteoarthritis (OA) development, the specific movement of the posterior horn of the medial meniscus (MM) during extrusion, particularly in early-stage OA, remains unexplored. Therefore, in this study, we investigated the position of the MM in patients with medial knee pain and a Kellgren-Lawrence grade ≤1, investigating the relationship between meniscal extrusion and degenerative tears. We hypothesized that the MM extrusion (MME) would be larger when degenerative tears are present; the anterior horn would move posteriorly, and the posterior horn would move anteriorly, accordingly.

Methods

A total of 181 knees (mean age 61.7 ± 12.1 years; 97 men and 84 women) were included. Simple radiographs were used to measure the weight-bearing line ratio and medial proximal tibia angle. Magnetic resonance imaging was used to measure the medial proximal tibia slope, medial meniscus extrusion, anterior and posterior horn position, and degenerative tears on the posterior segment of the medial meniscus. Those with degenerative tears were designated as group T and those without were designated as group C. Student's t-test and Pearson's χ2 test were performed to compare groups T and C. Statistical significance was set at p < 0.05.

Results

Group T had a significantly larger medial posterior tibial slope (group T: 7.4 ± 2.3°; group C: 6.6 ± 2.2°, p = 0.010) and medial meniscus extrusion (group T: 2.7 ± 1.4 mm; group C: 1.9 ± 1.2 mm, p < 0.001) scores compared with group C. Furthermore, the posterior point of the anterior horn (group T: 16.3 ± 5.0 %; group C: 14.3 ± 3.8 %, p = 0.004) and anterior point of the posterior horn (group T: 36.4 ± 7.1 %; group C:26.9 ± 5.9 %, p < 0.001) were significantly larger in group T than in group C.

Conclusion

Degenerative MM tears cause not only MME but also an anteroposterior shift.

Modulation of early osteoarthritis by tibiofemoral re-alignment in sheep

OBJECTIVE

To investigate whether tibiofemoral alignment influences early knee osteoarthritis (OA). We hypothesized that varus overload exacerbates early degenerative osteochondral changes, and that valgus underload diminishes early OA.

METHOD

Normal, over- and underload were induced by altering alignment via high tibial osteotomy in adult sheep (n = 8 each). Simultaneously, OA was induced by partial medial anterior meniscectomy. At 6 weeks postoperatively, OA was examined in five individual subregions of the medial tibial plateau using Kellgren-Lawrence grading, quantification of macroscopic OA, semiquantitative histopathological OA and immunohistochemical type-II collagen, ADAMTS-5, and MMP-13 scoring, biochemical determination of DNA and proteoglycan contents, and micro-computed tomographic evaluation of the subchondral bone.

RESULTS

Multivariate analyses revealed that OA cartilaginous changes had a temporal priority over subchondral bone changes. Underload inhibited early cartilage degeneration in a characteristic topographic pattern (P ≥ 0.0983 vs. normal), in particular below the meniscal damage, avoided alterations of the subarticular spongiosa (P ≥ 0.162 vs. normal), and prevented the disturbance of otherwise normal osteochondral correlations. Overload induced early alterations of the subchondral bone plate microstructure towards osteopenia, including significantly decreased percent bone volume and increased bone surface-to-volume ratio (all P ≤ 0.0359 vs. normal).

CONCLUSION

The data provide high-resolution evidence that tibiofemoral alignment modulates early OA induced by a medial meniscus injury in adult sheep. Since underload inhibits early OA, these data also support the clinical value of strategies to reduce the load in an affected knee compartment to possibly decelerate structural OA progression.

Medial meniscus extrusion is invariably observed and consistent with tibial osteophyte width in elderly populations: The Bunkyo Health Study

We reported that the full-length width of medial tibial osteophytes comprising cartilage and bone parts correlates with medial meniscus extrusion (MME) in early-stage knee osteoarthritis (OA). However, no data exist on the prevalence of MME and its relationship with osteophytes in the elderly population. 1191 elderly individuals (females 57%; 72.9 years old on average) in the Bunkyo Health Study underwent standing plain radiograph and proton density-weighted MRI on knee joints. MRI-detected OA changes were evaluated according to the Whole-Organ Magnetic Resonance Imaging Score. A new method of assessing the cartilage and bone parts of osteophytes was developed using pseudo-coloring images of proton density-weighted fat-suppressed MRI. Most subjects showed Kellgren-Lawrence grade 1 or 2 radiographic medial knee OA (88.1%), MME (98.7%, 3.90 ± 2.01 mm), and medial tibial osteophytes (99.3%, 3.27 ± 1.50 mm). Regarding OA changes, MME was closely associated with the full-length width of medial tibial osteophytes (β = 1.114; 95% CI 1.069-1.159; p < 0.001) in line with osteophyte width (intraclass correlation coefficient, 0.804; 95% CI 0.783-0.823). Our data revealed that MME and medial tibial osteophytes are observed in the elderly and demonstrate that the degree of MME is consistent with the full-length width of medial tibial osteophytes, suggesting that osteophytes might be implicated in MME.