The estimated number is between and The adult human skeletal system has a complex architecture that includes named bones connected by cartilage, tendons, ligaments, and three types of joints:. Although the actual number of joints in any one person depends on a number of variables, the estimated number is between and Cartilage cushions joints and helps them work smoothly.
It naturally degenerates with age, which may lead to osteoarthritis. Learn more. There are endless options when it comes to supplements that claim to reduce joint pain, but which ones actually work? Find out what exams and screenings are recommended for men at every stage of life, as well as tips on what to ask your doctor.
Subscription boxes are the gift that keeps on giving. Here are a few of our top picks. A subtendinous bursa is found between a tendon and a bone. Examples include the subacromial bursa that protects the tendon of shoulder muscle as it passes under the acromion of the scapula, and the suprapatellar bursa that separates the tendon of the large anterior thigh muscle from the distal femur just above the knee.
A tendon sheath is similar in structure to a bursa, but smaller. It is a connective tissue sac that surrounds a muscle tendon at places where the tendon crosses a joint. It contains a lubricating fluid that allows for smooth motions of the tendon during muscle contraction and joint movements. Bursitis can be either acute lasting only a few days or chronic. It can arise from muscle overuse, trauma, excessive or prolonged pressure on the skin, rheumatoid arthritis, gout, or infection of the joint.
Repeated acute episodes of bursitis can result in a chronic condition. Treatments for the disorder include antibiotics if the bursitis is caused by an infection, or anti-inflammatory agents, such as nonsteroidal anti-inflammatory drugs NSAIDs or corticosteroids if the bursitis is due to trauma or overuse. Chronic bursitis may require that fluid be drained, but additional surgery is usually not required. Synovial joints are subdivided based on the shapes of the articulating surfaces of the bones that form each joint.
The six types of synovial joints are pivot, hinge, condyloid, saddle, plane, and ball-and socket-joints Figure 9. At a pivot joint , a rounded portion of a bone is enclosed within a ring formed partially by the articulation with another bone and partially by a ligament see Figure 9.
The bone rotates within this ring. Since the rotation is around a single axis, pivot joints are functionally classified as a uniaxial diarthrosis type of joint.
An example of a pivot joint is the atlantoaxial joint, found between the C1 atlas and C2 axis vertebrae. Here, the upward projecting dens of the axis articulates with the inner aspect of the atlas, where it is held in place by a ligament. Rotation at this joint allows you to turn your head from side to side. A second pivot joint is found at the proximal radioulnar joint.
Here, the head of the radius is largely encircled by a ligament that holds it in place as it articulates with the radial notch of the ulna. Rotation of the radius allows for forearm movements. In a hinge joint , the convex end of one bone articulates with the concave end of the adjoining bone see Figure 9. This type of joint allows only for bending and straightening motions along a single axis, and thus hinge joints are functionally classified as uniaxial joints.
A good example is the elbow joint, with the articulation between the trochlea of the humerus and the trochlear notch of the ulna. Other hinge joints of the body include the knee, ankle, and interphalangeal joints between the phalanges of the fingers and toes. At a condyloid joint ellipsoid joint , the shallow depression at the end of one bone articulates with a rounded structure from an adjacent bone or bones see Figure 9.
The knuckle metacarpophalangeal joints of the hand between the distal end of a metacarpal bone and the proximal phalanx are condyloid joints. Another example is the radiocarpal joint of the wrist, between the shallow depression at the distal end of the radius bone and the rounded scaphoid, lunate, and triquetrum carpal bones.
In this case, the articulation area has a more oval elliptical shape. Functionally, condyloid joints are biaxial joints that allow for two planes of movement. One movement involves the bending and straightening of the fingers or the anterior-posterior movements of the hand. The second movement is a side-to-side movement, which allows you to spread your fingers apart and bring them together, or to move your hand in a medial or lateral direction.
At a saddle joint , both of the articulating surfaces for the bones have a saddle shape, which is concave in one direction and convex in the other see Figure 9. This allows the two bones to fit together like a rider sitting on a saddle. Saddle joints are functionally classified as biaxial joints.
The primary example is the first carpometacarpal joint, between the trapezium a carpal bone and the first metacarpal bone at the base of the thumb. This joint provides the thumb the ability to move away from the palm of the hand along two planes. Thus, the thumb can move within the same plane as the palm of the hand, or it can jut out anteriorly, perpendicular to the palm. The sternoclavicular joint is also classified as a saddle joint. At a plane joint gliding joint , the articulating surfaces of the bones are flat or slightly curved and of approximately the same size, which allows the bones to slide against each other see Figure 9.
The motion at this type of joint is usually small and tightly constrained by surrounding ligaments. Based only on their shape, plane joints can allow multiple movements, including rotation and can be functionally classified as a multiaxial joint.
However, not all of these movements are available to every plane joint due to limitations placed on it by ligaments or neighboring bones. Depending upon the specific joint of the body, a plane joint may exhibit movement in a single plane or in multiple planes. Plane joints are found between the carpal bones intercarpal joints of the wrist or tarsal bones intertarsal joints of the foot, between the clavicle and acromion of the scapula acromioclavicular joint , and between the superior and inferior articular processes of adjacent vertebrae zygapophysial joints.
The joint with the greatest range of motion is the ball-and-socket joint. At these joints, the rounded head of one bone the ball fits into the concave articulation the socket of the adjacent bone see Figure 9. The hip joint and the glenohumeral shoulder joint are the only ball-and-socket joints of the body. At the hip joint, the head of the femur articulates with the acetabulum of the hip bone, and at the shoulder joint, the head of the humerus articulates with the glenoid cavity of the scapula.
Ball-and-socket joints are classified functionally as multiaxial joints. The femur and the humerus are able to move in both anterior-posterior and medial-lateral directions and they can also rotate around their long axis. The shallow socket formed by the glenoid cavity allows the shoulder joint an extensive range of motion. In contrast, the deep socket of the acetabulum and the strong supporting ligaments of the hip joint serve to constrain movements of the femur, reflecting the need for stability and weight-bearing ability at the hip.
Watch this video to see an animation of synovial joints in action. Synovial joints are places where bones articulate with each other inside of a joint cavity. The different types of synovial joints are the ball-and-socket joint shoulder joint , hinge joint knee , pivot joint atlantoaxial joint, between C1 and C2 vertebrae of the neck , condyloid joint radiocarpal joint of the wrist , saddle joint first carpometacarpal joint, between the trapezium carpal bone and the first metacarpal bone, at the base of the thumb , and plane joint facet joints of vertebral column, between superior and inferior articular processes.
Which type of synovial joint allows for the widest range of motion? Risk factors that may lead to osteoarthritis later in life include injury to a joint; jobs that involve physical labor; sports with running, twisting, or throwing actions; and being overweight. These factors put stress on the articular cartilage that covers the surfaces of bones at synovial joints, causing the cartilage to gradually become thinner.
As the articular cartilage layer wears down, more pressure is placed on the bones. The joint responds by increasing production of the lubricating synovial fluid, but this can lead to swelling of the joint cavity, causing pain and joint stiffness as the articular capsule is stretched. The bone tissue underlying the damaged articular cartilage also responds by thickening, producing irregularities and causing the articulating surface of the bone to become rough or bumpy. Joint movement then results in pain and inflammation.
In individuals with more advanced osteoarthritis, the affected joints can become more painful and therefore are difficult to use effectively, resulting in increased immobility. There is no cure for osteoarthritis, but several treatments can help alleviate the pain. Treatments may include lifestyle changes, such as weight loss and low-impact exercise, and over-the-counter or prescription medications that help to alleviate the pain and inflammation.
For severe cases, joint replacement surgery arthroplasty may be required. Joint replacement is a very invasive procedure, so other treatments are always tried before surgery. This acts as a shock absorber and reduces friction as the bones move over each other. Together with the ligaments, tendons and muscles, the capsule keeps the bones of the joint in place. Author: myDr. Previous article Motor neurone disease. Next article Pleurisy: what you need to know. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits.
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