Joints Provide growth and movements to the body. There are two ways that we can classify joints: Functional & Structural
Functional Classification Synarthroses: immovable joints Ex: sutures of the skull Amphiarthroses: slightly movable Ex: pubic symphysis or intervertebral joints Diarthroses: freely movable
Flexibility Varies in Diarthrotic Joints Non-axial: allows only slipping. Plane Joints Ex: wrist Uniaxial: move in one plane. Ex: elbow Biaxial: move in 2 planes Ex: saddle joint (thumb) Multiaxial: move in all planes Ex: ball & socket (shoulder)
Distinguishing Features of Diarthrotic Joints 1. Articular Cartilage: Hyaline cartilage covers the ends of the bones forming the joint. 2. Fibrous articular capsule: joint surfaces are enclosed by a capsule of fibrous connective tissue, and the capsule is lined with a smooth synovial membrane =Synovial Joints
3. Joint Cavity: the articular capsule encloses a cavity, which contains synovial fluid. 4. Reinforcing Ligaments: Capsule is usually reinforced by ligaments.
Now… For the Structural Classifications But first…… Some Key terms: Ligament: strong, tensile, connective tissue cords that serve the function of uniting bones. Bursae: closed fibrous sacs that are filled with viscous fluid. Frequently located near joints where tendons are subject to frictional forces. Synovial Tendon Sheaths: bursal sacs that surround certain tendons.
3 Basic Structural Types Fibrous Cartilaginous Synovial Fibrous and Cartilaginous joints lack a joint cavity. Synovial Joints have a joint cavity.
Fibrous Joints Permit little or no movement Synarthroses or Amphiarthroses Participating bones bound together by fibrous connective tissue. 3 Specific Types Sutures, Gomphoses, Syndesmoses
Sutures Bones of the skull Sutural ligament: thin, intervening layer of fibrous connective tissue. With age this ligament is transformed into bone.
Gomphoses Gomphosis: peg and socket type joint. Synarthrosis Teeth fixed to maxilla and mandible by gomphoses.
Syndesmoses Amphiarthroses (slightly movable) Similar to suture Ex: distal tibiofibular joint Common sprain location
Cartilaginous Joints Lacks a joint cavity Participating bones held together by intervening cartilage. Permit little or no movement 2 Types: Symphyses Synchondroses
Symphysis Ex: Pubic Symphysis 2 bones held together by interpubic disc consisting of fibrocartilage. Amphiarthrotic. Why? Ex: Vertebrae seperated by intervertebral disks.
Synchondroses Temporary joint of hyaline cartilage Involved in growth Ex: Epiphyseal cartilaginous plate
Synovial Joints Articulating bones are separated by a fluid- containing joint cavity.
Structure of Synovial Joints Articular cartilage covers ends of bones. Participating bones bound together by fibrous capsule. It imparts strength and flexibility. Attached to periosteum of participating bones Synovial Cavity surrounds portions of bones in the formation. Synovial Membrane: thin membrane that lines all nonarticular aspects of the joint.
Synovial membranes produce synovial fluid. Nutritive and friction reducing properties. Synovial membrane is not present on articular cartilages. In certain synovial joints, accumulations of adipose tissue occur within the synovial membrane = articular fat pads = increase surface area of synovial membrane and facilitate distribution of synovial fluid.
Synovial Fluid Viscous fluid with clear or pale yellow tint. Contains various cell types: macrophages free synovial cells various white blood cells A cells: possess phagocytic activity. Remove debris and infectious organisms. Produce Hyaluronic Acid (viscosity)
Reinforcing Ligaments Limit abnormal, excessive motion. Ex: hyperextension of the knee Named according to their location with respect to their attachment. Accessory ligaments: distinct structures that can be located in an intracapsular (ACL, PCL) as well as extracapsular position.
Meniscus or Articular Disk Menisci consist predominantly of fibrocartilage. Found where articular surfaces lack congruity. Add to the stability of the joint. May divide joint cavity into 2 separate compartments, each with own synovial membrane. Exact function unknown. Proposed: spread of synovial fluid, shock absorption
Major forms of joint disorders Dislocation: displacement of a bone from it’s joint. May be accompanied by injury to ligaments, tendons, and fibrous capsule. Inflamation: inflammatory involvement of joints is known as arthritis. Most commonly found in hip, knee, elbow, ankle, wrist, and shoulder.
Gouty Arthritis Gout is a systemic disorder of uric acid metabolism. Chronic form of gout is characterized by deposition of uric acid crystals on articular surfaces of joints and by the formation of tophi in fibrous capsule and other connective tissue structures near joint. Tophi: Uric acid crystals surrounded by cells that are typical of an inflammatory response.
Treatment of Gout Gout is treatable, and there are ways to keep it from coming back. Treatment usually consists of: Nonsteroidal anti-inflammatory drugs to relieve symptoms. Steroidal anti-inflammatory drugs, such as prednisone While there is no way to guarantee that another attack of gout won't occur, a number of steps can reduce the risk of a future attack. These include: Taking drugs to slow the production and speed elimination of uric acid Maintaining a healthy weight, which reduces the pressure on weight-bearing joints and may decrease uric acid levels. Weight loss should be done in a slow, steady way because fasting or rapid weight loss can temporarily raise uric acid levels. Avoiding too much animal protein. These foods contain purines. Limiting or avoiding alcohol Drinking plenty of liquids. Fluids help dilute uric acid in the blood and urine.
Osteoarthritis Most common form of arthritis. Articular cartilage deteriorates and becomes eroded. New bone in the form of “spurs” forms at the periphery. Some of these may break off and lie free in the synovial cavity. “Joint Mice” No known cure.
Rheumatiod Arthritis Chronic inflammation of many body tissues, especially joints. Most commonly peripheral joints. Cause in unknown, but data suggests autoimmunity.
If uncontrolled, joint inflammation progresses in four stages: 1. First stage, synovitis (inflammation of the synovial membrane) develops from congestion of the synovial membrane and the joint capsule.synovitis 2. Formation of pannus (thickened layers of granulation tissue) marks the onset of the second stage. Pannus covers and invades cartilage and eventually destroys the joint capsule and bone. 3. The third stage is characterized by fibrous ankylosis - fibrous invasion of the pannus and scar formation that occludes the joint space. Bone atrophy and misalignment cause visible deformities and disrupt the articulation of opposing bones. 4. In the fourth stage, fibrous tissue calcifies, resulting in bony ankylosis and total immobility.