Shoulder Joint - The Most Flexible Joint in the Body
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Shoulder Joint - The Most Flexible Joint

Dr.Surya Rao Poodipeddi profile Authored by Dr.Surya Rao Poodipeddi on 18 Apr 2014 - 09:16.

Amongst all the joints in the human body the shoulder joint is the one which is used more than the other joints. It is the most mobile joint in the body and it has the capability to turn in many directions.

The shoulder joint is a ball & socket type of joint, like its counterpart the hip joint. However, the shoulder joint has a wider range of movements. It can move the arm to a full circle both ways and abduct (move the arm away from the midline of the body) the upper limb up to 180 degrees. If over used, like in strenuous sport activities involving the shoulder joint, there is a possibility for a rupture of the muscles responsible for its movements, especially the deltoid.

Shoulder Joint Anatomy

Four muscles come into picture in the act of abduction of the arm over the shoulder joint, namely the Deltoid, Supraspinatus, Serratus Anterior and Trapezius. The last two muscles assist the other two in abducting the arm past the horizontal plane.

The shoulder joint is made of three bones namely, the shoulder blade (Scapula) the Collarbone (Clavicle) and the bone in the upper arm (Humerus) .The humeral head which is the head of the upper arm rests in glenoid socket in the shoulder blade and hence it is called a ball and socket joint. However, the head of the humerus is slightly larger than the glenoid cavity. To obviate this problem and fit the head perfectly into the socket a soft fibrous tissue rim called the labrum surrounds the socket to stabilize the joint. The rim helps deepen the socket by about 50 percent to enable a better fit of the head into the socket.

The joint needs perfect reinforcement to avoid slipping (dislocation) of the head in any direction. This is accomplished by the strong ligaments attached to the rim of the socket which pass across the joint and help secure the head firmly with in the socket.

The tissue rim surrounding the shoulder socket is vulnerable to several injuries like acute (sudden) trauma and repetitive shoulder movements. Important examples of a traumatic injury include:

  1. Falling down with hand stretched out
  2. Direct attack on the shoulder
  3. Involved in a sudden pulling of heavy object
  4. Preventing a fall or a slide violently with the hand overhead
  5. Athletes involved in the act of throwing or weightlifting are more vulnerable for tears in the muscles.

A tear in the rim can occur above (superior) or below (inferior) the middle of the glenoid cavity. A tear above the middle of the socket may involve the tendon meant for the biceps muscle. A tear below the middle of the glenoid may lead to a condition called Bankart lesion where the lower glenohumeral ligament may get torn. Tears in the rim of the glenoid may result from any type of shoulder dislocation (full or partial).

It becomes difficult to diagnose a tear in the shoulder socket because most of the symptoms are similar to those in other types of injury to the shoulder joint. Important symptoms include:

  • Pain, which is more common in over head injuries.
  • There may be a catching or a locking of the joint.
  • Occasional pain in the joint during night or during daily activities.
  • There may be a feeling of instability in the shoulder.
  • The range of joint movements is decreased.
  • Loss of strength in the joint.

Diagnosis is based on the presence of pain in the shoulder and history of some injury either past or present. It needs careful examinations of all the movements over the shoulder joint to determine the range of movements and loss if any.

An X-ray of the shoulder joint should include the collarbone and the scapula to detect any fracture in and around the bones that form the shoulder joint.

An X-ray cannot detect the injury in a muscle or the soft rim. Therefore an MRI (Magnetic Resonance Image) is an absolute necessity in cases where every other investigation doesn’t throw any light in the diagnosis especially when the pain is chronic in nature. Even if this fails to diagnose, one needs to rely on C

Initial treatment consists of anti-inflammatory drugs and resting the part with mild to moderate exercises depending on the severity of injury with a view to rehabilitating the joint. If theses conservative measures fail to give relief, one may need arthroscopic surgery both as a means to diagnose and repair the fault.

Research Being Done on Shoulder Problems:

Scientists are studying shoulder problems to find ways to:

  • Improve surgery methods
  • ​Improve shoulder function and reduce pain.
  • Correct the movement patterns which cause shoulder pain in some people, with spinal cord damage.
  • Develop new medicines that help muscles and tendons heal.
  • Prevent and treat rotator cuff tears.

Details about arthroscopic surgery and procedures of various types of tears in and around the shoulder socket, as well as other conditions affecting the shoulder joint will be covered in the Part II of the article.



*Disclaimer: This is not medical advice. The content is for educational purposes only. Please contact your doctor for any health care issues.