In anatomy, a “facet” refers to a smooth, flat surface on a bone that forms a joint with another bone. These specialized surfaces are part of synovial joints, which are characterized by a fluid-filled capsule that allows for movement. Facets play a significant role in providing movement and stability within the skeletal system, enabling a wide range of motions while maintaining structural integrity.
Where Facet Joints are Found
Facet joints, also known as zygapophysial joints, are located throughout the spine. Two facet joints are located between each pair of vertebrae at the back (posterior) of the spinal column. These small, paired joints connect the superior articular process of one vertebra with the inferior articular process of the vertebra directly above it. The surfaces within these joints are covered with articular cartilage, allowing for smooth movement, and are enclosed by a fibrous joint capsule that contains lubricating synovial fluid.
These joints extend from the cervical (neck) to the lumbar (lower back) regions of the spine. Their orientation differs at various spinal levels, influencing the specific movements possible in each section. For instance, cervical facet joints are generally oriented at about 45 degrees, allowing for a wide range of motion, including flexion, extension, lateral bending, and rotation. Thoracic facet joints are more vertically aligned, limiting flexion and extension but facilitating rotation, while lumbar facet joints are oriented closer to the sagittal plane, primarily allowing for flexion and extension and limiting twisting movements.
How Facet Joints Function
Facet joints guide spinal movement, allowing a controlled range of motion while limiting excessive motion that could lead to injury. They permit movements such as flexion (bending forward), extension (bending backward), rotation (twisting), and lateral bending (side-to-side movement).
These joints work with intervertebral discs to share weight-bearing loads and maintain spinal stability. They absorb compressive and shear forces placed on the spine during activities like standing, walking, and lifting. By preventing excessive movement between adjacent vertebrae, facet joints contribute to spinal stability and protect the spinal cord and nerve roots.
Understanding Facet Joint Conditions
Facet joints can be affected by various issues, with age-related wear and tear being common. This process can lead to conditions such as osteoarthritis (facet arthropathy), where the cartilage covering the joint surfaces wears thin. Inflammation or injury to these joints can also occur, causing discomfort and limiting mobility.
These conditions often result in symptoms such as localized pain in the neck or lower back, stiffness, and reduced range of motion. Pain might worsen with specific movements, such as bending backward or twisting, or after periods of inactivity. Diagnosis typically involves a physical examination and imaging studies (X-rays, CT scans, or MRI) that can show changes consistent with facet joint conditions. Management often includes non-surgical approaches such as rest, physical therapy to strengthen supporting muscles, and medications to reduce inflammation and pain.