Chapter 8: Joints

Q1: What are the functional and structural classifications of human joints, and give examples of each?

• Functional Classifications:

  1. Synarthrosis: No movement allowed 

  2. Amphiarthrosis: Some movement allowed “Slightly moving”

  3. Diarthrosis: Freely moveable 

• Structural Classifications:

  1. Fibrous Joints (Fibers): Dense regular collagenous connective tissue

     • Suture: Skull bones held together by short fibrous connective tissue fibers 

     • Gomphosis: Tooth within bony cavity held by periodontal ligament (Peg-in-socket)

     • Syndesomoses: Dense regular collagen connective tissue between 2 long bones (ligaments only) like radius and ulna & tibia and fibula 

  2. Cartilaginous Joints: Has cartilage 

     • Synchodrosis: Hyaline cartilage plate between bones 

       • An example is the first rib (sternocostal joint)

     • Symphysis: Fibrocartilage pad between the 2 articulating bones 

  3. Synovial Joints: Looks like an egg; a movement between 2 or more bones 

     • Plane Joint: Nonaxial; Flat bone surfaces glide across one another 

     • Hinge Joint: Uniaxial; The convex surface of one bone fits into the concave surface of another bone to allow angular motion along an axis 

     • Pivot Joint: Uniaxial; Projection of one bone fits into another bone; the second bone rotates around the first 

     • Condyloid Joint: Biaxial; Convex oval surface of one bone articulates with the concave oval surface of another bone 

     • Saddle Joint: Biaxial; Saddle-shaped surface of one bone sits into a depression of another bone 

     • Ball-and-socket Joint: Multiaxial; Round head of one bone fits into a cup-shaped surface of another bone 

Q2: What is the structure of a typical synovial joint?

• Must haves for Synovial joints 

1. Aicular Capsule/Joint with a synovial membrane 

   1. Synovial membrane- makes synovial fluid 

2. Got to have joint cavity with synovial fluid 

   1. Synovial fluid is a somewhat thick yellowish fluid

      1. Lubrates 

      2. Shock absorber 

      3. Protein 

      4. Hyaluronic acid in it 

3. Articular Cartilage 

   1. Is the hyaline cartilage at the end of the articulating bones it's still in there from endochondral ossification

• Might/possibly haves for synovial joints 

1. Tendon Sheath & Bursa are both bags of synovial fluid 

   1. Bursa might be found between 2 large bony processes like acromion and humerus 

   2. Tendon Sheath is a bag of synovial fluid that wraps around the tendons 

Q3: Define uniaxial, biaxial, and multiaxial joints.

• Uniaxial Joints: Only allow motion around 1 axis, like hinge joints 

• Biaxial Joints: Allows motion around 2 axes, like the metacarpal-proximal phalanx joints 

• Multiaxial Joints: Allows the motion around more than 2 axes, like the ball-in-socket shoulder joint 

Q4: What are the types of synovial joint movements?

• Angular Movements:

  • Flexion: A motion that makes a joint angle smaller on the anterior side of the body (elbow flexion)

  • Extension: A motion that makes a joint angle larger on the anterior side of the body (elbow extension) 

  • Abduction: Moving a body part away from the midline of the body (the upswing) -Upper limb abduction

  • Adduction: Moving a body part toward the midline of the body (the downswing) -Upper limb adduction

  • Circumduction: A large circular motion of a joint (ball-in-socket joints can do this)

• Rotation: Pivoting around an axis (rotation toward the front = medial/ internal rotation)

• Special Movements:

  • Pronation/Supination: Turning the palm up/down (the forearm)

  • Dorsiflexion/Plantar Flexion: Turning the ankle up/down 

  • Inversion/Eversion: Turing the sole of the foot inward/outward 

Q5: What are the structural classifications of synovial joints?

1. Plane Joint: Nonaxial; Flat bone surfaces glide across one another 

2. Hinge Joint: Uniaxial; The convex surface of one bone fits into the concave surface of another bone to allow angular motion along an axis 

3. Pivot Joint: Uniaxial; Projection of one bone fits into another bone; the second bone rotates around the first 

4. Condyloid Joint: Biaxial; Convex oval surface of one bone articulates with the concave oval surface of another bone 

5. Saddle Joint: Biaxial; Saddle-shaped surface of one bone sits into a depression of another bone 

6. Ball-and-socket Joint: Multiaxial; Round head of one bone fits into a cup-shaped surface of another bone 

Q6: What is the structure and function of the shoulder and hip joints?

• Shoulder Joint:

  • Structure: The ball-and-socket joint, shallow glenoid cavity 

  • Movements: The wide range is flexion, abduction, and rotation 

  • Injuries: It is prone to dislocations and the rotator cuff to injuries 

• Hip Joint:

  • Structure: The ball-and-socket joint, has a deep acetabulum

  • Movements: The flexion, extension, abduction, and rotation

  • Injuries: Has is less prone to dislocation, but fractures become common in the elderly

Q7: Define luxation, subluxation, and rotator cuff injury.

• Luxation: The complete dislocation of a joint 

• Subluxation: The partial dislocation of a joint 

• Rotator Cuff Injury: Tears or strain of the muscles and the tendons that stabilize the shoulder joint

Q8: Describe the knee joint's structure, movements, and injuries.

• Structure:

  • Largest and most complex joint.

  • It includes the femur, tibia, and patella 

  • It is stabilized by the medial collateral ligament (ACL, PCL) and the tendon 

• Movements: Flexion, extension, and a slight rotation 

• Injuries:

  • ACL tears with a forceful twist 

  • The Medical collateral ligament (MCL) can be injured by a sharp turn

  • Both of the collateral ligaments (MCL and LCL) can be injured by side impacts

Q9: How can knee injuries be predicted based on force and direction of impact?

• Lateral Force: Likely damages the medial collateral ligament ( MCL) because it is connected to the femur to the tibia 

• Twisting Force: Often tears the Anterior cruciate ligament (ACL) from moving forward  

• Direct Blow: Is caused by hyperextension to the knee and allows the tibia to move too far anteriorly on the femur

Q10: What are the three types of arthritis?

1. Osteoarthritis: 

   1. Normal wear and tear

   2. Most common type 

   3. Articular cartilage wears down 

   4. Replace damaged cartilage with bone 

   5. Bone spurs 

2. Rheumatoid Arthritis:

   1. 3x more common in females 

   2. Autoimmune where we attack our own articular cartilage 

3. Gouty Arthritis:

   1. More in males 

   2. Too much uric acid in blood 

      1. Crystals from in joints 

      2. Often toe joints (the big toe)

Definitions

1. Arthroscopy: Minimally invasive joint surgery using a camera.

2. Goniometer: Tool to measure joint range of motion.

3. Arthroplasty: Surgical joint replacement.

4. Active Range of Motion: Movements performed by the individual.

5. Passive Range of Motion: Movements performed by an external force.