Lesson 4: Synovial Joints

Learning synovial joints is an important step toward understanding human movement and starting a career as a sports medicine professional. The skeletal system of the human body is comprised of various joint types; however, synovial joints are the most common. Their unique structure allows for more motion than fibrous joints (also known as immovable joints), and cartilaginous joints (partly moveable joints). The amount of motion is due to the unique joint anatomy of synovial joints, which include a joint capsule, synovial fluid, articular cartilage covering bone surfaces, articular discs, intricate ligament systems to support motion, and often bursae.

The synovial joint type, joint shape, joint structure, cartilage, and connective tissue determine how much motion is permitted. Examples of synovial joint types include ball and socket, hinge, pivot, gliding, saddle, and condyloid. Each joint type allows motion in a specific number of planes, and the joint type and available planes of motion correspond to specific joint actions. For example, the elbow joint is a hinge joint, which only allows motion in one plane (sagittal plane), which corresponds to the joint actions of flexion and extension (e.g. biceps curls and triceps extensions). Whereas, the shoulder joint is a ball and socket joint, which allows motion in all three planes (sagittal, frontal, and transverse), which correspond with the joint actions of flexion, extension, abduction, adduction, horizontal abduction, horizontal adduction, internal rotation, and external rotation (e.g. horizontal adduction during a bench press). Less commonly mentioned joints include the gliding joints of the carpal bones (wrist bones), the saddle joint of the carpometacarpal joint (thumb), or the pivot joint of the proximal radioulnar joint (forearm). Note the lower limb has the same joint types, including a ball and socket joint (hip joint), hinge joint (knee joint), and gliding joints (transverse tarsal joints).

Sports medicine professionals (personal trainers, fitness instructors, physical therapists, athletic trainers, massage therapists, chiropractors, occupational therapists, etc.) must be aware of synovial joint types for the analysis of motion and the development of sophisticated exercise programs and therapeutic (rehabilitation) interventions. Note, this lesson builds on the previous lesson discussing joint actions, and will be essential knowledge for further lessons discussing the muscles of the hip joint, knee joint, ankle joint, spine, etc. Further, this course is essential knowledge for future courses discussing biomechanics, muscle synergies, movement dysfunction and pain, posture, physical therapy (physical rehabilitation), sports science, sports performance, etc.

For more advanced anatomy check out our integrated functional anatomy courses:

• Shoulder Joint Anatomy
• Sternoclavicular (SC), Acromioclavicular (AC), and Scapulothoracic (ST) Joint Anatomy
• Cervical Spine Anatomy
• Hip Joint Anatomy
• Knee Joint Anatomy
• Ankle Joint Anatomy

Caption: Ball and socket joint displaying a large range of motion