The ball-and-socket joint (or spheroid joint) is a type of synovial joint in which the ball-shaped surface of one rounded bone fits into the cup-like depression of another bone. The distal bone is capable of motion around an indefinite number of axes, which have one common center. This enables the joint to move in many directions.
Examples of this form of articulation are found in the hip, where the round head of the femur (ball) rests in the cup-like acetabulum (socket) of the pelvis; and in the shoulder joint, where the rounded upper extremity of the humerus (ball) rests in the cup-like glenoid fossa (socket) of the shoulder blade. (The shoulder also includes a sternoclavicular joint.)
Did you know that there are between 250-350 joints in the human body? The reason why this is not an exact number is because the number of joints can vary with age, the number of sesamoids can vary, and the definition of joints can either be the point at which two bones connect or the point where bones connect for the purpose of movement.
When it comes to joint problems and injuries, synovial joints are affected far more than fixed or cartilaginous joints. For this reason, we will be looking closely at the different types of synovial joints, where they are found in the body, and what problems or injuries commonly affect them. There are six different types of synovial joints, including:
Ball and socket joints are composed of one bone with a rounded head that fits into the cup of another bone. Since the rounded head can move freely within the cup, or socket, this allows for movement in all directions. Common ball and socket joints include the hips and shoulders. Osteoarthritis is a common problem seen in the hip joints that occurs as the lubricating cartilage of the joint degenerates. In the shoulder, it is common to develop rotator cuff tendinitis, which is a swelling of the tendons that support the rotator cuff.
Hinge Joints open and close in a single direction, much like a door. Some examples of hinge joints include fingers, toes, ankles, elbows, and knees. Like ball and socket joints, hinge joints can be affected by osteoarthritis as the joint degenerates. Additionally, hinge joints are also prone to dislocation and tissue damage from sports injuries.
Condyloid joints, also known as ellipsoid joints, are composed of an egg-shaped bone known as a condyle that fits into a similarly shaped cavity. Although it sounds similar to a ball and socket joint, condyloid joints only allow for forward-backward and side to side movement and do not allow rotation. An example of condyloid joints is the wrist. Condyloid joints are also found in the hands and allow for the movement of fingers. Sprains, carpal tunnel syndrome, and arthritis are common problems that can affect the condyloid joints and surrounding structures.
Also known as rotary joints or trochoid joints, pivot joints are composed of one bone that swivels within the ring of a second bone allowing for rotation. The joint between the ulna and radius, as well as the joint between the first and second vertebrae are pivot joints. Pivot joints can dislocate, fracture, become sprained or strained, and be affected by wear and tear problems, such as arthritis.
Also known as the plane joint, gliding joints are composed of two smooth surfaces that slide over one another to produce limited movement. They are primarily found in the ankles, wrist, and spine. Like the other joints in the body, plane joints can be affected by arthritis.
Saddle joints are composed of one bone that is concave, resembling a saddle, and another bone that is convex, resembling a rider. They are found in the thumb, shoulder, and inner ear, and allow for a variety of movement in multiple directions. Saddle joints are especially prone to osteoarthritis.
A joint is a point where two bones are attached and are capable of movement. The joints not only provide the movements of limbs but also provide stability (like the stability or hardness of the skull). The main function of joints is to hold the skeleton in a position and provide support in movements.Joints can be categorized in two ways:
A condyloid joint is a type of synovial joint where the articular surface (meaning, the connection between the bones) of one bone has an ovoid convexity sitting within an ellipsoidal cavity of the other bone. (Yakut & Tuncer, 2020)
The condyloid joint is a type of synovial joint. In one articular surface of the bone, there is an ovoid convexity in which it articulates with other bone having an ellipsoidal cavity. This joint allows rotation but no movement. For example, jaw and finger joints are condyloid joints.
The condyloid joint is also named a condylar joint, bicondylar, or ellipsoid joint. The following figure shows a condyloid joint. In Figure 2, the oval shape end of one bone articulates with the oval shape hollow of another bone. (Manganaro, Dollinger, Nezwek, & Sadiq, 2019) For example, the metacarpophalangeal joint is a collection of condyloid joints that connects the metacarpus to the fingers. This is also an ellipsoid joint example.
In condyloid joints, the articular capsule is present among the two joined bones. Articular cartilage is the cover that protects the synovial joint. Certain adjacent ligaments to the joint provide support. They also help in preventing the injury by limiting the movement.
Like saddle joints, condyloid joints permit movement with two degrees of freedom. Movement like abduction/adduction, flexion/extension (circumduction) is allowed at such joints. Axial rotation is allowed at the ball and socket joint but not at the condyloid joint. In other words, condyloid joints have non-axial movements. However, limited circumduction can be possible at such joints due to the oval shape of joints.
Although the fingers are small, limited circular motion is possible. The bottom joint of each finger is a condyloid joint. In the proper functioning of the hand, these joints have an important role. With the help of joint capsules, surrounding musculotendinous structures, and ligaments, flexibility and stability of fingers can be achieved. (Yakut & Tuncer, 2020)
Extension and flexion are the main movements at the condyloid joint. Almost 90 flexion, 10 extension in the index finger, and 30 extension in the little finger are possible. In the 3rd to 5th condyloid joint, flexion is accompanied by mild lateral rotation and in the 2nd condyloid joint it is accompanied by mild medial rotation.
In the condyloid joint, about 25-30 full range of motion is possible around the axis. This small range of motion links to abduction. Due to collateral ligaments and the width and shape of the metacarpal head, the movement is restricted. Neither abduction nor adduction can be achieved in the condyloid joint during flexion. This happens due to the arrangement of collateral ligaments. Adduction and abduction are followed by the movements in the corresponding carpometacarpal joints.
In circumduction, the distal end of the limb moves circularly while the proximal end remains fixed. It includes the combination of adduction, abduction, flexion, and extension on a joint. This movement is possible at the multiaxial ball and socket joints, biaxial condyloid, and saddle joints.
The ball and socket configuration allows for movement with 3 degrees of freedom, which is more than any other type of synovial joint. The depth of the cup and any additional fibrocartilaginous labrum is the major limitation to the extent of motion allowed in any direction.
The point at which two bones lay adjacent to each other (with or without the ability to move) is called a joint. The joints of the human body have been classified based on the range of motion they exhibit and by the type of tissue that holds the neighboring bones together.
Synovial joints are the freely mobile joints in which the articulating surfaces have no direct contact with each other. The movement range is defined (i.e., limited) by the joint capsule, supporting ligaments and muscles that cross the joint. Most of the upper and lower limb joints are synovial.
Further reinforcement of the capsule is provided by ligaments, tendons and skeletal muscle. These joints are capable of a large range of motions and consequently, are the most susceptible to dislocations. There are several examples of synovial joints, all of which are capable of an eclectic arrangement of motions. These include the:
In contrast to synovial joints, fibrous joints are far simpler and less mobile. The articulating edges of bones are attached by fibrous connective tissue. Motion at these joints is negligible. Fibrous joints are found only in three areas throughout the body.
In the skull, by three years of age, all the fontanelle (soft regions between cranial bones) would have fused. The remnants, referred to as cranial sutures, are fibrous connections (sutural ligaments) that occupy the joint space. The adjacent bones will completely ossify with time, which may result in obliteration of the suture lines.
Cartilaginous joints are chiefly characterized by the fact that they connect with neighboring bones via cartilage. They exhibit a range of motion that falls between synovial and fibrous joints. There are two types of cartilaginous joints, synchondrosis and symphysis joints.
Symphysis (secondary cartilaginous) joints are the second group of cartilaginous joints. They are found primarily along the midline of the body. The joint features include adjacent bone surfaces lined with hyaline cartilage and connected by fibrous tissue with some degree of mobility. The intervertebral joints, pubic symphysis and the manubriosternal angle of Louis are all examples of symphysis joints. In some instances there may be joint cavities, but they are never synovial in nature. 041b061a72