Which of the following statements best explains why ball-and-socket joints of the greatest range of motion?

Shoulders and hips are often described using the “ball and socket” comparison. Over the past few weeks, I have seen an increase in shoulder conditions in the office, even more frequently than hip complaints. When discussing the anatomy with the patient, I always mention the term “ball and socket,” but I like to take it a step further and explain how the shoulder is different from the hip.

If you try moving your shoulder, you notice that it can go 360 degrees around in rotation, whereas the hip hits some hard end ranges.  This is due to the nature of the ball and socket joint. A good way to note difference is by thinking of the shoulder as more of a golf ball sitting on a golf tee and the hip as a true ball in socket.  

After looking at the anatomy above, you can see the shoulder joint is made up of the head of the humerus, which rests on the glenoid fossa of the scapula (or shoulder blade).  Where as the hip joint is the head of the femur that fits into the acetabulum of the ilium (pelvic bones). So, as one of my college professors always said, this makes the shoulder like one of your family members, a little unstable (he had some jokes!).

This means that shoulder injuries are normally more soft tissue in nature.  The shoulder blade itself is a floating bone, adhered to the back of the ribs by muscles. The humerus is held to the shoulder blade by the 4 muscles that make up the rotator cuff. The only joint holding your shoulder girdle to the rest of your body is the sternoclavicular joint – the area where your collarbone meets your chest bone. 

The hip joint is a little tricky because of the way our bodies develop, and it is a tough area to work on.  It is more weight bearing so, yes, we do have a lot of muscles around it. However, the joint itself can suffer from degeneration and things like femoral acetabular impingement (where the head of the femur does not fit like Cinderella’s slipper in the acetabulum). We’ll discuss this more next time!

But back to the shoulder. If you do suffer from shoulder pain, think more about muscle involvement before anything else.  Some self-tests you can do are looking at rotation: Can you make an entire circle with your arm without pain? Does your arm get stuck in certain places if you rotate it up? How about rotating it down? Is there numbness, tingling, or loss of strength? If most of your tests only produce pain with movement and not loss of strength or change in sensation, you may benefit from soft tissue manipulation and other chiropractic modalities rather than needing more invasive procedures right away!

As always, consult with a healthcare provider regarding your shoulder pain. Conservative treatment such as graston, myofascial release and therapies may be beneficial to get you back to your active life style.  If you have any questions feel free to call Stumpff Chiropractic at 954-368-4054 or visit www.stumpffchiro.com for more information.  

Learning Outcomes

• Identify the six types of synovial joints

Synovial joints are further classified into six different categories on the basis of the shape and structure of the joint. The shape of the joint affects the type of movement permitted by the joint (Figure 1). These joints can be described as planar, hinge, pivot, condyloid, saddle, or ball-and-socket joints.

Figure 1. Different types of joints allow different types of movement. Planar, hinge, pivot, condyloid, saddle, and ball-and-socket are all types of synovial joints.

Planar Joints

Planar joints have bones with articulating surfaces that are flat or slightly curved faces. These joints allow for gliding movements, and so the joints are sometimes referred to as gliding joints. The range of motion is limited in these joints and does not involve rotation. Planar joints are found in the carpal bones in the hand and the tarsal bones of the foot, as well as between vertebrae (Figure 2).

Figure 2. The joints of the carpal bones in the wrist are examples of planar joints. (credit: modification of work by Brian C. Goss)

Hinge Joints

In hinge joints, the slightly rounded end of one bone fits into the slightly hollow end of the other bone. In this way, one bone moves while the other remains stationary, like the hinge of a door. The elbow is an example of a hinge joint. The knee is sometimes classified as a modified hinge joint (Figure 3).

Figure 3. The elbow joint, where the radius articulates with the humerus, is an example of a hinge joint. (credit: modification of work by Brian C. Goss)

Pivot Joints

Pivot joints consist of the rounded end of one bone fitting into a ring formed by the other bone. This structure allows rotational movement, as the rounded bone moves around its own axis. An example of a pivot joint is the joint of the first and second vertebrae of the neck that allows the head to move back and forth (Figure 4). The joint of the wrist that allows the palm of the hand to be turned up and down is also a pivot joint.

Figure 4. The joint in the neck that allows the head to move back and forth is an example of a pivot joint.

Condyloid Joints

Condyloid joints consist of an oval-shaped end of one bone fitting into a similarly oval-shaped hollow of another bone (Figure 5). This is also sometimes called an ellipsoidal joint. This type of joint allows angular movement along two axes, as seen in the joints of the wrist and fingers, which can move both side to side and up and down.

Figure 5. The metacarpophalangeal joints in the finger are examples of condyloid joints. (credit: modification of work by Gray’s Anatomy)

Saddle Joints

Saddle joints are so named because the ends of each bone resemble a saddle, with concave and convex portions that fit together. Saddle joints allow angular movements similar to condyloid joints but with a greater range of motion. An example of a saddle joint is the thumb joint, which can move back and forth and up and down, but more freely than the wrist or fingers (Figure 6).

Figure 6. The carpometacarpal joints in the thumb are examples of saddle joints. (credit: modification of work by Brian C. Goss)

Ball-and-Socket Joints

Ball-and-socket joints possess a rounded, ball-like end of one bone fitting into a cuplike socket of another bone. This organization allows the greatest range of motion, as all movement types are possible in all directions. Examples of ball-and-socket joints are the shoulder and hip joints (Figure 7).

Figure 7. The shoulder joint is an example of a ball-and-socket joint.

Watch this animation showing the six types of synovial joints.

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