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Patients with unilateral hip osteoarthritis show a characteristic gait pattern in which they unload the affected leg and overload the unaffected leg. Information on the gait characteristics of patients with bilateral hip osteoarthritis is very limited. The main purposes of this study were to investigate whether the gait pattern of both legs of patients with bilateral hip osteoarthritis deviates from healthy controls and whether bilateral hip osteoarthritis patients show a more symmetrical joint load compared to unilateral hip osteoarthritis patients. In this prospective study, 26 patients with bilateral hip osteoarthritis, 26 patients with unilateral hip osteoarthritis and 26 healthy controls were included. The three groups were matched for gender, age and walking speed. Patients were scheduled for a unilateral total hip arthroplasty on the more affected/more painful side. All participants underwent a three-dimensional gait analysis. Gait kinematics and gait kinetics of patients and controls were compared using Statistical Parametric Mapping. Corrected for speed, the gait kinematics and kinetics of both legs of patients with bilateral hip osteoarthritis differed from healthy controls. Bilateral patients had symmetrical knee joint loading, in contrast to the asymmetrical knee joint loading in unilateral hip osteoarthritis patients. The ipsilateral leg of the bilateral patients could be included in studies in addition to unilateral hip osteoarthritis patients as no differences were found. Although patients with bilateral hip osteoarthritis show more symmetrical frontal plane knee joint moments, a pathological external knee adduction moment in the second half of stance was present in the ipsilateral leg in patients with unilateral and bilateral hip osteoarthritis. The lateral adjustment of the knee adduction moment may initiate or accelerate progression of degenerative changes in the lateral compartment of the knee.
In recent years, the infrapatellar fat pad (IFP) has gained increasing research interest. The contribution of the IFP to the development and progression of knee osteoarthritis (OA) through extensive interactions with the synovium, articular cartilage, and subchondral bone is being considered. As part of the initiation process of OA, IFP secretes abundant pro-inflammatory mediators among many other factors. Today, the IFP is (partially) resected in most total knee arthroplasties (TKA) allowing better visualization during surgical procedures. Currently, there is no clear guideline providing evidence in favor of or against IFP resection. With increasing numbers of TKAs, there is a focus on preventing adverse postoperative outcomes. Therefore, anatomic features, role in the development of knee OA, and consequences of resecting versus preserving the IFP during TKA are reviewed in the following article.
Matrix metalloproteinases (MMPs) play crucial roles in tissue homeostasis and pathologies by remodeling the extracellular matrix. Previous studies have demonstrated the biological activities of MMP-derived cleavage products. Furthermore, specific fragments can serve as biomarkers. Therefore, an in vitro cleavage assay to identify substrates and characterize cleavage patterns could provide important insight in disease-relevant mechanisms and the identification of novel biomarkers. In the pathogenesis of osteoarthritis (OA), MMP-2, -8, -9 and -13 are of vital importance. However, it is unclear which protease can cleave which matrix component. To address this question, we established an in vitro cleavage assay using recombinantly expressed MMPs and the two cartilage matrix components, COMP and thrombospondin-4. We found a time- and concentration-dependent degradation and an MMP-specific cleavage pattern for both proteins. Cleavage products can now be enriched and purified to investigate their biological activity. To verify the in vivo relevance, we compared the in vitro cleavage patterns with serum and synovial fluid from OA patients and could indeed detect fragments of similar size in the human samples. The cleavage assay can be adapted to other MMPs and substrates, making it a valuable tool for many research fields.