Elsevier

Medical Hypotheses

Volume 85, Issue 2, August 2015, Pages 207-211
Medical Hypotheses

Role of medial abrasion phenomenon in the pathogenesis of knee osteoarthritis

https://doi.org/10.1016/j.mehy.2015.04.028Get rights and content

Abstract

Osteoarthritis of the knee affects a large population worldwide and is associated with an extremely high economic burden largely attributable to the effects of disability, comorbid disease, and the expense of treatment. Since the initiating events that result in the cartilage degradation are poorly understood, there has been very limited success in demonstrating disease modification in clinical trials of potential therapies. Medial plica related medial abrasion phenomenon has recently been identified to have close relationship with medial compartment osteoarthritis. We hypothesized that this abrasion phenomenon will elicit lifelong interplay between pathologic medial plica and the facing medial femoral condyle and might play a role in the pathogenesis of knee osteoarthritis by both physical and chemical effects. After evaluating current evidence, we designed a study to prove that the concentrations of total protein, cartilage degrading related cytokines (tumor necrosis factor-α and interleukin-1β) and enzyme (matrix metalloproteinase-3) are higher in the medial compartment of the knee having the phenomenon of medial abrasion. The accumulating data and findings about medial abrasion phenomenon might be important for the understanding of the pathogenesis or progression of this common disease. We hope that our hypothesis will stimulate further studies verifying if medial abrasion phenomenon plays more roles in the pathogenesis of knee osteoarthritis. Further clinical observations for its appropriate treatment based on this hypothesis are also mandatory for the benefits of patients.

Introduction

Osteoarthritis (OA) of the knee is the major cause of chronic musculoskeletal pain and is ranked as a main reason of mobility disability in elderly population. It is a disease process of uncertain multifactorial etiology, which eventually affects the entire joint. Various etiologic risk factors have been proposed, but the exact pathogenesis for OA knee is unknown so far.

Many literatures mentioned medial compartment is more commonly involved than the lateral one and the pathogenesis may be different [1], [2], [3], [4], [5], [6], [7]. In 2006, it was reported that in patients with medial compartment osteoarthritic knees, the prevalence of medial plica was significantly higher than that of others and that two distinct foci of cartilaginous lesion were found on the facing medial femoral condyle in almost all of the patients who had the structure of medial plica [8]. A further study disclosed the kinematic relationship of the medial plica with the medial femoral condyle during knee motion in vivo [9]. In that study, it was revealed that all medial plicae, regardless of their size, would move reciprocally and would keep in touch with the medial femoral condyle and therefore might cause some degree of abrasion on the facing medial femoral condyle during knee motion. Another histomorphological study of the medial plica also implied the close interplay between this structure and the medial femoral condyle in patients with knee OA [10].

Section snippets

The hypothesis

We postulated that in the knee having the structure of medial plica demonstrating medial abrasion phenomenon, the repeated abrasion and impingement between medial plica and medial femoral condyle would elicit both physical and chemical effects on the adjacent cartilage and the medial plica itself which might play a role in the pathogenesis of knee OA.

Construction of three-dimensional dynamic finite element model

An experimental study on the tensile strength of the medial plica from 50 knees was conducted using high precision micro-force tensile tests [11]. The force–deflection curves resulting from these tests were transferred to stress–strain curves to obtain Young’s moduli of these specimens. In another selected 30 knees with different sizes of medial plica [9], the inner margins of the plicae were located by inserting needles percutaneously under direct vision during arthroscopic examination. The

New evidence: total protein, TNF-α, IL-1β and MMP-3 concentrations are higher in the medial compartment of the knee with medial abrasion phenomenon

There are a variety of proteins or debris in the synovial fluid of osteoarthritic knee. These proteins include glycoprotein debris and collagen fragments derived from destructed cartilaginous tissue and enzymes such as metalloproteinase, collagenase and proinflammatory cytokines (ILs, TNF-α, etc) [17], [18], [19]. All of these proteins in synovial fluid might reflect the pathological status of the knees. It has been reported that cartilage debris in the traumatized and osteoarthritic joint may

Consequences of the hypothesis and conclusion

In summary, our hypothesis points to the role of medial abrasion phenomenon in the pathogenesis of knee OA. There is accumulating evidence to suggest that both the physical and chemical effects elicited by the lifelong interplay between medial plica and the facing medial femoral condyle may contribute to the development and progression of knee OA. The consequent clinical applications of this hypothesis have provided benefits to the patients. If our hypothesis is confirmed by further

Conflict of interest

There is no conflict of interest.

Contributions

SR Lyu designed the study, provided materials, drafted and critically revised the article for important intellectual content. JY Cherng, YC Huang, CH Li, YJ Lin and CM Chang collected, assembled and statistically analyzed the data. CY Chiang and LK Chau analyzed and interpreted the data, drafted and finally approved the article.

Acknowledgement

This work was supported by the Tzu-Chi Dalin General Hospital, Chiayi, Taiwan.

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