Ligaments: Structure, Function, and Key Examples

Ligaments are dense regular connective tissue bands that connect bone to bone, providing passive joint stability and guiding joint kinematics.

Structural Composition

• Primarily Type I collagen fibers arranged in parallel bundles for high tensile strength.
• Sparse fibroblast-like cells (ligamentocytes) maintain the matrix.
• Poor vascularity limits healing capacity compared to muscle or bone.
• Innervated by mechanoreceptors (proprioception) and nociceptors (pain).

Biomechanical Functions

• Limit excessive translation and rotation (passive stability).
• Guide joint motion along physiological paths.
• Provide proprioceptive feedback for neuromuscular control.

Major Ligaments by Joint

• Knee: ACL, PCL, MCL, LCL.
• Ankle: ATFL, CFL, PTFL (lateral); Deltoid ligament (medial).
• Shoulder: Glenohumeral ligaments (superior, middle, inferior), coracohumeral ligament.
• Spine: Anterior/posterior longitudinal ligaments, ligamentum flavum, interspinous/supraspinous ligaments.

Terminology & Injury Grading

• Latin: ligamentum (singular), ligamenta (plural).
• Sprain = ligament injury: Grade I (microscopic tear), Grade II (partial tear), Grade III (complete rupture).
• Laxity = excessive length/looseness, congenital or acquired.