Articular System & Arthrokinematics

1. Joint: articulation between bones; functions by allowing movement and providing stability  

   • Carries weight during posture/gait 

   • Can allow a lot of motion (shoulder) or minimal movement (sternoclavicular joint) 

   • Move movement = less stability 

2. Arthrokinematics: joint surface movement 

1. Bones: shape of ends determine the amount/direction of joint movement 

2. Ligaments: bands of fibrous connective tissue, supports and holds a joint together; flexible but not elastic 

   • Flexibility = movement 

   • non-elastic = protection and prevents excessive movement 

   • Capsular ligament: fully encompasses a synovial joint 

     • Synovial membrane: thick, vascular connective tissue that secretes synovial fluid 

     • Synovial fluid: thick, clear fluid consisting of water/dissolved protein 

       • Function: lubricates the articular cartilage to reduce friction, major source of nutrition for articular cartilage; shock absorption 

   • Intraarticular ligament: ligaments that occur within the joint (ex. ACL) 

3. Cartilage: dense, fibrous connective tissue that can withstand pressure & tension 

   • Hyaline cartilage (articular cartilage): covers ends of opposing bones within a synovial joint 

     • Lacks blood/nerve supply; synovial fluid provides nutrition 

     • Cannot repair itself 

   • Fibrocartilage: present in synovial and cartilaginous joints primarily responsible for shock absorption & altering articular joint surfaces 

     • Ex. Labrum: fibrocartilaginous ring in the scapular portion of the shoulder joint 

     • Ex. Intervertebral discs: cartilage between the bodies of vertebrae that absorbs stresses imposed on the vertebrae 

   • Elastic cartilage: designed to help maintain a structure's shape while allowing flexibility 

     • Ex. External ear & larynx (important for speech) 

4. Tendon: connects muscle to bone; cylindrical cords or flat bands 

   • Muscles provide contractile force to cause movement 

   • Tendon sheath: fibrous sleeves lubricated by secreted fluid surrounding a tendon to reduce the friction or pressure when passing between muscles/bones 

     • Ex. Span the tendons in the wrist 

   • Aponeurosis: broad, flat, tendinous sheet of connective tissue that attaches muscle to bone 

     • Thoracolumbar fascia: the connection between the latissimus dorsi muscle attaching to the origin spanning numerous bones via a aponeurosis 

     • Linea alba: an aponeurosis located in the midline of the anterior abdominal wall attaching the internal oblique and transverse abdominus 

5. Bursae: small, synovial fluid-filled, pillow-like sacs located near joints lined with synovial membranes to provide cushioning and reduce friction 

   • Ex. Knee joints 

   • Natural v. acquired bursae 

     • Acquired bursae: in areas that do not normally have excessive friction but develop when abnormal friction occurs 

       • Can disappear or reduce when activity is reduced/stopped

End Feel: sensation a clinician perceives when passively moving a patient's joint to the end of its ROM used to identify the reason for limitation of motion 

• Overpressure: additional pressure needed at the end of available motion to elicit an end feel 

Normal - occurs when joint motion is limited as expected 

• 1. Soft end feel (soft tissue approximation): occurs when compression of muscle bulk halts movement 

  2. Firm end feel: results from tension in structures (ligaments, capsule, muscle) surrounding a joint and is perceived as first resistance to movement with only a slight give on overpressure 

  3. Hard end feel (bony end feel): characterized by hard/abrupt limitation of passive joint motion with no give on overpressure 

     • Created by bone contacting bone at the end of motion 

Abnormal - presents when pain, muscle guarding, swelling, or abnormal anatomy limits joint movement; types of described by explaining the source of limitation 

• 4. Boggy end feel: soft, "wet sponge" feel occurring in acute condition with soft tissue swelling  

  5. Muscle spasm: reflexive muscle guarding during movement used as a protective response with acute injuries 

  6. Empty end feel: occurs when movement produces pain and patient stops movement of the joint beyond the painful point of joint motion 

  7. Springy block: a rebound movement, occurring with internal derangement of a joint (ex. Torn cartilage) 

Roll, glide, & spin - necessary for joint mobility 

• All joint movement involves at least one arthrokinematic movement 

  1. Roll: movement of one surface rolling on an adjacent surface; a new point on one joint surface contacts a new point on the adjacent surface throughout the movement  

     • Ex. Knee flexion/extension 

  2. Glide: (slide) linear movement of one joint surface parallel to the plane of an adjacent joint surface; a single point of joint surface contacts new points on the adjacent joint surface through movement  

  3. Spin: rotation of a single point on joint surface on a single point on the adjacent joint surface; the same point on each joint surface remains in contact throughout the movement 

1. Dislocation: complete separation of the articular surfaces of a joint resulting from disruption of supporting structures (joint capsule & ligaments) 

2. Subluxation: partial dislocation of a joint 

3. Osteoarthritis (degenerative arthritis): type of arthritis caused by wear and subsequent breakdown of cartilage; commonly caused by aging & repetitive motion 

4. Sprains: tears of ligaments and capsules 

   1. First degree - mild; involving tearing of a few ligament fibers and no loss of function  

   2. Second degree - moderate; involves partial tearing with some loss of function 

   3. Third degree - severe; full rupture (tearing) of a ligament that no longer functions 

5. Strain: feres to the overstretching of muscle fibers 

   1. First degree - mild; involving tearing of few muscle fibers and no loss of fxct 

   2. Second degree - moderate; partial tearing of a muscle with some loss of fxct 

   3. Third degree - severe; full rupture of muscle that no longer generates force 

6. Inflammation: normal response to injury marked by localized swelling, redness, increased temperature, & pain 

   1. Tendonitis: inflammation of a tendon 

   2. Synovitis: inflammation of a synovial membrane 

   3. Tenosynovitis: inflammation of a tendon sheath caused by repetitive use 

   4. Bursitis: inflammation of a bursa 

   5. Capsulitis: inflammation of a joint capsule - can lose its extensibility = loss of joint motion 

7. Capsular pattern: characteristic pattern of each joint of lost motion when capsular tightness is present