Multiple Subchondral Bone Cysts Cause Deterioration of Articular Cartilage in Medial OA of Knee: A 3D Simulation Study

In Silico Modeling of Stress Distribution in the Diseased Ankle Joint

Background/Objectives: Osteoarthritis is a feature of the aging process. Here, we adopted in silico 2D finite element modeling (FEM) for the simulation of diseased ankle joints. We delved into the influence of body weight intensity on the stress distribution caused by subchondral cysts imitating degenerative age-related arthritic changes. Methods: FEM was performed using virtually generated pictorial schemes of the ankle joint skeletal contour. It included a constellation of scenarios with solitary or multiple cysts, or the lack thereof, located centrally, peripherally, or both in the talus and tibia at increased fixed levels of body weight. Results: The modeling showed that the highest stress was in the presence of a solitary central cyst in the talus and two centrally located cysts in the talus and the tibia, with the averaged values of 1.81 ± 0.52 MPa and 1.92 ± 0.55 MPa, respectively; there was a significant increase compared with the 1.24 ± 0.35 MPa in the control condition without cysts. An increase in body weight consistently increased the strain on the ankle joint. In contrast, peripherally located cysts failed to affect the stress distribution significantly. Conclusions: We conclude that subchondral central cysts substantially enhance the stress exerted on the ankle joint and its vicinity with body weight dependence. FEM's ability to predict the location and magnitude of subchondral stress changes when confirmed in clinical trials might help to optimize the management of age-related degenerative joint changes.

Pathological progression of osteoarthritis: a perspective on subchondral bone

Osteoarthritis (OA) is a degenerative bone disease associated with aging. The rising global aging population has led to a surge in OA cases, thereby imposing a significant socioeconomic burden. Researchers have been keenly investigating the mechanisms underlying OA. Previous studies have suggested that the disease starts with synovial inflammation and hyperplasia, advancing toward cartilage degradation. Ultimately, subchondral-bone collapse, sclerosis, and osteophyte formation occur. This progression is deemed as "top to bottom." However, recent research is challenging this perspective by indicating that initial changes occur in subchondral bone, precipitating cartilage breakdown. In this review, we elucidate the epidemiology of OA and present an in-depth overview of the subchondral bone's physiological state, functions, and the varied pathological shifts during OA progression. We also introduce the role of multifunctional signal pathways (including osteoprotegerin (OPG)/receptor activator of nuclear factor-kappa B ligand (RANKL)/receptor activator of nuclear factor-kappa B (RANK), and chemokine (CXC motif) ligand 12 (CXCL12)/CXC motif chemokine receptor 4 (CXCR4)) in the pathology of subchondral bone and their role in the "bottom-up" progression of OA. Using vivid pattern maps and clinical images, this review highlights the crucial role of subchondral bone in driving OA progression, illuminating its interplay with the condition.

Model Properties and Clinical Application in the Finite Element Analysis of Knee Joint: A Review

The knee is the most complex joint in the human body, including bony structures like the femur, tibia, fibula, and patella, and soft tissues like menisci, ligaments, muscles, and tendons. Complex anatomical structures of the knee joint make it difficult to conduct precise biomechanical research and explore the mechanism of movement and injury. The finite element model (FEM), as an important engineering analysis technique, has been widely used in many fields of bioengineering research. The FEM has advantages in the biomechanical analysis of objects with complex structures. Researchers can use this technology to construct a human knee joint model and perform biomechanical analysis on it. At the same time, finite element analysis can effectively evaluate variables such as stress, strain, displacement, and rotation, helping to predict injury mechanisms and optimize surgical techniques, which make up for the shortcomings of traditional biomechanics experimental research. However, few papers introduce what material properties should be selected for each anatomic structure of knee FEM to meet different research purposes. Based on previous finite element studies of the knee joint, this paper summarizes various modeling strategies and applications, serving as a reference for constructing knee joint models and research design.

The relationship between subchondral bone cysts and cartilage health in the Tibiotalar joint: A finite element analysis

BACKGROUND

Subchondral bone cysts are a common presentation in ankle haemarthropathy. The relationship with ankle joint health has however not previously been investigated. The aim of this study was to assess the influence of subchondral bone cysts of differing shapes, volumes and depths on joint health.

METHODS

Chronologically sequential Magnetic Resonance imaging scans of four hemophilic ankles with subchondral bone cysts present (N = 18) were used to build patient specific finite element models under two cystic conditions to assess their influence on cartilage contact pressures. Variables such as location, volume and depth were considered individually, to investigate whether certain cystic conditions may be more detrimental to cartilage health.

FINDINGS

Significant quantifiable contact redistribution was seen in the presence of subchondral bone cysts and this redistribution reflected the shape and size of the cysts, however, with the presence of cysts in both bones in 10 of the 18 cases a direct relationship to volume could not be correlated.

INTERPRETATION

This work demonstrated a redistribution of contact pressures in the presence of subchondral bone cysts. This alteration to loading history could be linked to cartilage degeneration due to the biological response to abnormal loading.