Ligaments and Tendons (11/17)
What is the structure of tendons? What tissue surrounds the tendons? What is their special role?
Dense regular connective tissues - Type 1 collagen (86%) and Type III collagen (5%) Epitenon and paratenon surround the fascicles Specialized to transmit high tensile loads from muscle to bone
What are three mechanisms of injury to tendons?
Direct trauma/laceration Indirect trauma w/intrasubstance injury or bone avulsion (sudden tensile stress) Repetitive submaximal overload or repetitive pressure against bony surface
What is Enthesis? What is the difference between direct and indirect attachment of ligaments?
Enthesis = attachment Direct attachment involves 4 zones of continuous collagen fibers of increasing density, leading to calcification (ligament --> fibrocartilage --> calcified fibrocartilage --> bone) Indirect attachment has no fibrocartilage, the ligaments merge into the periosteal layer --> not as strong
What is the physiologic structure of ligaments? What does this translate into as far as function?
Highly aligned collagen fascicles, which crimp to provide "non-linearity" --> At low loads, they straighten out but are still lax, whereas at high loads the fibrils stretch and become more stiff
What are the 4 zones of insertion of tendons? What are Sharpey's fibers?
Tendon --> Fibrocartilage --> Mineralized fibrocartilage --> Bone Collage bundles extending from tendon or periosteum into the bone
What are the differences between ligaments and tendons?
Tendon: - Uniformly stiff - Does not elongate --> Allows conservation of energy Ligament - Built-in laxity - Allows small forces across joint - Protect joint
What are the two types of tendons? What are examples of each one?
Tendons that pull in straight lines (eg. Achilles tendon)- these are not enclosed by a sheath, but a paratenon, which is loose connective tissues continuous with the tendon Tendons required to bend (eg. flexor tendons of hand) - these are enclosed by a tendon sheath guiding the tendon path, and acting like a pulley. Motion is assisted by synovial fluid produced by epitenon
What is proprioception? What is the role of ligaments in proprioception?
brains way of knowing where the joint is in space Nerve fibers in ligament which can be disrupted due to injury...these nerve fibers take longer to heal than the actual ligament --> perception of instability --> physical therapy/rehab to bring perception back to normal
What are ligaments? What is their role? What is their function
- Fibrous soft tissue - Connect bone to bone - Allow normal joint motion - Prevent abnormal motion, instability --> loads pass across articulating surfaces - Redundancy across joints - Secondary restraint during normal activity under load (weight-bearing) - Guide unloaded motion (knee "screw home")...allows locking and unlocking of knee - Stop abnormal motion to avoid further damage - Strong in tension, weak in compression
What are the things involved in ligament maintenance?
Cells: Fusiform, ovoid, and spheroid Vascular supplies cells with nutrients: - Inside = endoligament - Outside = epiligament
What type of collagen makes up ligaments?
Collagen I (same as bone)
What are the different grades of ligament injuries? What are ligament injuries caused by? What type of injuries always include ligament injury?
Grade 1 - pain, no instability Grade 2 - some torn fibers, minimal instability (endpoint exists) Grade 3 - completely torn (no endpoint) Always from excessive tension Dislocations
What motions do the ankle ligaments guide? PCL? ACL?
Linear action of muscles into rotation Femoral rollback Screw-home
When do ligaments come into play to prevent injury with relationship to muscles?
Muscles are the first line of defense Ligaments come into play when muscles inactivate or are too weak