Related Experiment Video
Updated: Oct 16, 2026

A Pre-Clinical Model of Synovitis Using Ex vivo Human Synovial Tissue with Preserved Function and Architecture
Published on: March 20, 2026
Reconceptualizing Sacroiliac Joint Mechanics: From Independent Joints to a Unified Functional Unit
Abstract:
BACKGROUND: Pain localized to the area around the "Dimple of Venus" is a common clinical presentation in patients with low back pain (LBP). This region represents the most peripheral dorsal portion of the sacroiliac joint (SIJ). CLINICAL QUESTION: Although the SIJ is recognized as a source of unilateral LBP, its deep anatomical location and complex morphology make diagnosis difficult. Consequently, current clinical SIJ tests often yield inconsistent results, leading to skepticism regarding the joint's clinical relevance. This doubt is largely rooted in a historically accepted biomechanical model of movement that assumes the left and right SIJs move independently. KEY RESULTS: We propose a paradigm shift in which both SIJs function as 1 bicondylar unit rather than 2 independent joints. CLINICAL APPLICATION: By recognizing reciprocal SIJ motion, our revised bicondylar model simplifies diagnosis into 2 distinct mechanical disorders and could enhance the reliability, interpretation, and clinical utility of future SIJ evaluations. JOSPT Open 2026;4(4):377-384. Epub 27 August 2026. doi:10.2519/josptopen.2026.0241.
Related Concept Videos
Functional Classification of Joints
The functional classification of joints is determined by the amount of mobility between the adjacent bones. Joints are functionally classified as a synarthrosis or immobile joint, an amphiarthrosis or slightly moveable joint, or as a diarthrosis, a freely moveable joint. Fibrous and cartilaginous joints can be functionally classified as either synarthroses or amphiarthroses, whereas all synovial joints are classified as diarthroses.
Synarthrosis
An immobile...
Structural Joints: Synovial Joints
Joints
Structural joint classifications are based on the material that makes up the joint as well as whether or not the joint contains a space between the bones. Joints are structurally classified as fibrous, cartilaginous, or synovial.
Fibrous Joints Are Immovable
The bones of a...
Knee Joint
A total of seven ligaments support the knee joint. The patellar ligament, which is also attached to the quadriceps femoris group...
Development of the Limb Synovial Joints
The mesenchymal stem cells differentiate into chondrocytes that form the hyaline cartilage, and later the cartilaginous model of the bone. This model further transforms into a bone. This process is known as endochondral ossification.
During development, the limbs...
Introduction to Joints