gms | German Medical Science

Problem: To evaluate whether horizontal cleavage and complex meniscus tears are associated with an increase of specific matrix metalloproteinases and an increased incidence of cartilage damage, in comparison with patients having other patterns of meniscal injury.

Methods: Data were collected prospectively from 32 knee arthroscopies, patients were assigned by intraoperative findings due to their meniscal tear to one of two groups: "degenerative meniscal lesions" (horizontal cleavage and complex tears; n=20) or "traumatic tears" (longitudinal and radial tears; n=12). Samples of knee joint fluid were analyzed for the matrix matrix metalloproteinases pro-MMP-1, MMP-3 and pro-MMP-13, which are postulated to be involved in articular cartilage degradation. Cartilage changes were classified intraoperative by Outerbridge (grade 0–4). Praeoperative bone morphology of the knee joint was graduated by Kellgren-Lawrence (Stadium 0–4).

The Knee Injury and Osteoarthritis Outcome Score (KOOS) was used to assess the patients opinion about their knee and associated symptoms and function preoperative and 1.5 years postoperative.

Results and conclusions: Degenerative meniscus lesions appeared predominantly at the end of fifty years of age (58.5±13.9 years), whereas other patterns of meniscal lesions happened around 30 years of age (28.7±8.1 years; P<.0001). A comparison of patients with horizontal cleavage and complex meniscal tears ("degenerative tears") to patients with longitudinal or radial ("traumatic") tears showed for the former increased severity of chondral lesions (Outerbridge: 2.9±1.4 vs 1.1±0.9; P=.001) and radiographic osteoarthritis (Kellgren-Lawrence: 1.9±1.5 vs 0.4±0.5; P=.004). The KOOS improved after arthroscopic treatment in the degenerative-meniscal-tear group as well as in the traumatic-tear group significantly (Total-KOOS Score preoperative: 36.5±30.7 and 38.1±24.8; Total-KOOS Score 1.5 years postoperative: 87.8±6.7 and 49.2±21.9; p=.043 and p=.012; "0" indicates extreme knee problems; "100" indicates no knee problems; Fig. 4 [Median]). Pro-MMP-13 correlated significantly with an increase of chondral lesions and radiographic osteoarthritis (r=.534; p=.003; r=.457; p=.02). MMP-3 concentrations in the synovial fluid of patients with a degenerative meniscus lesion were about 20% higher compared to patients with other patterns of meniscal lesions. No one of the investigated MMPs correlated significantly with a specific meniscal injury (Fig. 5 [Median]).

Complex and horizontal cleavage meniscal tears are not as benign as was previously thought and are highly associated with an increased severity of cartilage degeneration and radiographic osteoarthritis. In spite of distinct cartilage changes arthroscopic treatment improved knee-related symptoms at least on medium-term also in patients with degenerative meniscal tears. In this study, specific meniscal lesions did not seem to be associated with increased concentrations of the investigated MMPs.