JOINTS

A joint or place of articulation is formed where 2 or more bones come inclose contact in the body and are attached to each other by ligaments or cartilage.

Types of Joints

Joints can be classified according to the degree and type of movement they allow. The following types of joints can be recognized:

Fibrous (or Immovable) Joints.

These joints are firmly held together by a thin layer of strong connectice tissue. There is no movement between the bones such as the sutures of the skull and the teeth in their sockets.

Fibrous joints (sultures in the skull).

Cartilagenous Joints.

Cartilagenous joints are joints where the articular surfaces of the bones forming the joints are attached to each other by means of white fibrocartilaginous discs and ligaments which allow only a limited degree of movement. Examples are the cartilaginous between the vertebrae, the cartilage in the symphysis which binds the pubic bones together at the front of the pelvic girdle and the cartilage in the joint between the sacrum and the hip bone.

Cartilaginous joints between the thoracic vertebrae.

Synovial Joints.

These are freely movable joints. Most of the joints in the body are of the synovial type. The following are the main characteristics of a synovial joint:

• The ends of the bones are covered with a layer of smooth hyaline cartilage, called articular cartilage in the joint regions. This reduces fricton at the point.
• The joint is completely enclosed by a bag-like capsular ligament which holds the joint together and helps to contain the synovial fluid.
• The capsular ligament is lined with a synovial membrane. This membrane secretes synovial fluid into the synovial cavity and acts as a seal, waterproofing the joint. The synovial fluid lubricates the joint.
• In addition to the capsule, the bones are also attached and held together by strong, tough ligaments made of dense connective tissue. These ligaments prevent dislocation during normal movement.
• The articulating surfaces of adjacent bones are reciprocally shaped.

A generalized synovial joint.

Synovial joints can be subdivided into the following groups according to the type of movement they carry out:

• Ball-and-Socket Joints.These joints are formed where the rounded head of one bone fits into the hollow, cup-shaped socket of another bone such as the shoulder joint and the hip joint. Such joints allow freedom of movement in all directions.
  
  

  The Hip Joint - ball-and-socket joint.

• Hinge Joints.These joints occur where the convex surface of one bone fits into the concave surface of another bone, so making movement possible in one plane only. Examples of these joints are the knee and the elbow joints. Hinge joints have ligaments mainly at the sides of the joints.
  
  

  A hinge joint (elbow region).

• Gliding Joints.This type of joint allows for gliding movements between flat surfaces as the surfaces slide over one another. Only a limited amount of movement is allowed such as the joints between the carpal bones, the joints between the tarsal bones and those between the articular processes (zygapophyses) of successive vertebrae.
  
  

  Gliding joints in the wrist region.

• Pivot Joints.These joints occur where:
  
  • a bony ring rotates round the pivot (axis) of another bone such as the ring-like atlas rotating around the odontoid process of the axis, allowing the head to turn from side to side.
  • the end of one one bone rotates round the axis of another bone such as the end of the radius rotating around the ulna as the palm of the hand is turned inwards or outwards.

  A pivot joint between the radius and ulna.

• Compound Joints.These joints are made up of several joints between a number of different bones. The bones articulate with one another in different ways, allowing for a variety of movements such as the set of joints which operate the movement of the skull on the vertebral column. The condyles at the base of the skull fit into the facets of the atlas, allowing for the nodding movement of the head. While one moves one's head, the atlas is able to rotate round the odontoid process of the axis, allowing the head to turn from side to side. There are also other articulating surfaces, where the atlas and axis meet. All these joints together make a compound joint with its many possible movements in the neck region.

Model showing compound joints in the neck region.

Joint disorders

A joint is where two or more bones come together, like the knee, hip, elbow or shoulder. Joints can be damaged by many types of injuries or diseases. Arthritis or simply years of use may cause a joint to wear away. This can cause pain, stiffness and swelling. Over time, a swollen joint can become severely damaged.

Treatment of joint problems depends on the cause. If you have a sports injury, treatment often begins with the RICE (Rest, Ice, Compression and Elevation) method to relieve pain, reduce swelling and speed healing. Other possible treatments include pain relievers, keeping the injured area from moving, rehabilitation, and sometimes surgery. For arthritis, injuries, or other diseases, you may need joint replacement surgery to remove the damaged joint and put in a new one.

Arthritis is a form of joint disorder that involves inflammation of one or more joints.

There are over 100 different forms of arthritis. The most common form, osteoarthritis (degenerative joint disease), is a result of trauma to the joint, infection of the joint, or age. Other arthritis forms are rheumatoid arthritis, psoriatic arthritis, and related autoimmune diseases. Septic arthritis is caused by joint infection.

The major complaint by individuals who have arthritis is joint pain. Pain is often a constant and may be localized to the joint affected. The pain from arthritis is due to inflammation that occurs around the joint, damage to the joint from disease, daily wear and tear of joint, muscle strains caused by forceful movements against stiff, painful joints and fatigue.

Osteoarthritis (OA) also known as degenerative arthritis or degenerative joint disease or osteoarthrosis, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion. A variety of causes—hereditary, developmental, metabolic, and mechanical—may initiate processes leading to loss of cartilage. When bone surfaces become less well protected by cartilage, bone may be exposed and damaged. As a result of decreased movement secondary to pain, regional muscles may atrophy, and ligaments may become more lax.

Treatment generally involves a combination of exercise, lifestyle modification, and analgesics. If pain becomes debilitating, joint replacement surgery may be used to improve the quality of life. OA is the most common form of arthritis, and the leading cause of chronic disability in the United States. It affects about 8 million people in the United Kingdom and nearly 27 million people in the United States.

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks flexible (synovial) joints. The process involves an inflammatory response of the capsule around the joints (synovium) secondary to swelling (hyperplasia) of synovial cells, excess synovial fluid, and the development of fibrous tissue (pannus) in the synovium. The pathology of the disease process often leads to the destruction of articular cartilage and ankylosis (fusion) of the joints. Rheumatoid arthritis can also produce diffuse inflammation in the lungs, membrane around the heart (pericardium), the membranes of the lung (pleura), and white of the eye (sclera), and also nodular lesions, most common insubcutaneous tissue. Although the cause of rheumatoid arthritis is unknown, autoimmunity plays a pivotal role in both its chronicity and progression, and RA is considered a systemic autoimmune disease.

Hip dysplasia, developmental dysplasia of the hip (DDH) or congenital dysplasia of the hip (CDH) is a congenital or acquired deformation or misalignment of the hip joint.

Swollen Knees