Which muscles are involved in upper back pain?

Trapezius muscle

Trapezius is a superficial broad triangular muscle at neck and upper back, one of the largest superficial muscles at the upper back. It attaches to the base of the skull and extends down to the neck, the upper back until mid back; laterally it inserts to the shoulder blades. There are three functional regions to the muscle: the Upper, middle, and lower trapezius, and each region has its own function: upper region moves the shoulder blades and support the arms; the middle region retracts the shoulder blades and the lower region rotates and depresses the shoulder blades.

Rhomboid major and minor muscles

Below Levator scapulae muscle are Rhoboids including rhomboids minor and rhomboids major.

Rhomboid minor and Rhomboids major are muscles on the back connecting the shoulder blade with the spinal column. Rhomboids major is just below the rhomboid minor. They are deeper to the trapezius starting from spinal column C7 to T5 and inserting to the medial border of the shoulder blade. They keep the shoulder blade pressed against the back and retracted the shoulder blade toward the spinal column. The innervation to these two muscles is from C4-C6 nerve root on the neck.

Trigger points present in trapezius and/or Rhomboids are a common cause of upper back pain.

The serratus posterior superior

Deep to the rhomboid muscles is the serratus posterior superior as mentioned above.

Acupuncture needles are inserted in trapezius trigger points are an efficient way to release upper back pain.

Shoulder pain and rotator cuff disorders

Rotator cuff disorders

Rotator cuff disorder is another common cause for shoulder pain.

The rotator cuff is a group of tendons and muscles in the shoulder, connecting the upper arm to the shoulder blade as mentioned above. The rotator cuff tendons provide stability to the shoulder; the muscles allow the shoulder to rotate. The rotator cuff keeps the joint in the correct position, allowing it to move in a controlled way. Rotator cuff disorders occur when these tendons and muscles get irritated or damaged. The disorders include inflammation of the tendons or bursa, impingement (a tendon is squeezed and rubs against bone), calcium building up and tears of the tendons. The most common causes are 1) normal wear and tear. Rotator cuff is damaged due to years of using the shoulder and changes in the rotator cuff, for instance thinning and wearing of the tendons and reduced blood supply. 2) overuse. Activities involved in using rotator cuff a lot such as tennis, swimming or painting or using over a prolonged period can stress or injure the rotator cuff. 3) rotator cuff injury. Too much over head lifting or throwing sports etc can injure rotator cuff.

The symptoms include pain and weakness in the shoulder and it is worse during the activities when the arm is above shoulder level – for example, when brushing the hair; when the arm is moving away from the body; pain is in the front and side of the shoulder.

Acupuncture is very effective to release shoulder pain. 

Which muscles are related shoulder pain?

Muscles surrounding the shoulder joint

Trapezius muscle

Trapezius muscle attaches to the base of the skull and extends down until mid back and laterally it inserts to the shoulder blades. It is involved in the shoulder blades movement

Pain caused by middle and lower part of the trapezius can present burning pain or aching on the top of the shoulder. Also pain caused by the lower part of the muscle can present upper shoulder pain; pain at the back of the shoulder blade which could radiate to the inside of the arm to the ring and little fingers.

Latissimus dorsi

Latissimus dorsi is the largest flat muscle in the back.

It originates from the inferior thoracic and lumbar vertebrae, sacrum, iliac crest, and the four most inferior ribs, runs laterally up through the back, inferior part of shoulder blades and inserts to the upper front of the humerus. This muscle plays a role in shoulder joint movement such as adducting the arms, extending the shoulders and rotating shoulder joints medially. Tight latissimus dorsi and the trigger points in the muscles could be one of the causes of shoulder pain, forearm pain, pain between shoulder blades, shoulder blades and pain in front of shoulder.

There are seven muscles that connect the upper arm to the shoulder blades.

Rotator cuff

Rotator cuff is a group of four muscles including supraspinatus muscle, the infraspinatus muscle, teres minor muscle, and the subscapularis muscle. They connect the scapula to the head to the humerus (arm) , stabilize shoulder joint and contribute to shoulder joint movement including abduction, internal rotation, and external rotation of the shoulder. Rotator cuff problem such as injury or overuse of these muscles can cause shoulder pain which is characterised as pain around the shoulder and reduced shoulder joint movement.

Teres major muscle

Teres major muscle also connects shoulder blades to the upper arms starting from lower angle of the shoulder blade and ending at the upper arm in the front of the shoulder. The teres major muscle is involved in adducting the arm, stabilising the humeral head, extending the shoulder and rotating it inwardly. The teres major trigger points cause pain at the back of the shoulder which can radiate to the front and side of the shoulder and down the backside of the arm.

Deltoid muscles

The deltoid muscle forms the rounded contour of the shoulder and is the big muscle on the shoulder. It has three parts; the front, middle and back. The front part is involved in flexing the shoulder and internally rotating the arm. The middle part is involved in shoulder abduction. The back part is involved in extending the shoulder and externally rotating the arm.

Coracobrachialis muscle

This is the smallest muscle that connects upper arm to the shoulder blade. It plays a part in adduction, flexion, and inward rotation of the arm. It also helps stabilise humeral head within the joint.

Muscles connected chest and shoulder

Pectoralis major and minor muscles

The pectoralis major muscle and the pectoralis minor muscle are the muscles located at the chest They are overlapped.

The pectoralis muscle originated from inner half of the clavicular bone, sternum as well as the cartilage of the sixth or seventh rib and the aponeurosis of the abdominal muscle. The muscle goes laterally and inserts to the upper arm. It adducts the arm and rotates the shoulder inwardly, pull down the shoulder joint and elevated the arm to the front. Pectoralis minor originates from 3-5 ribs and it runs upward and laterally and inserts to the surface of the coracoids process of the scapula. It pulls the shoulder blade downward, forward and inward towards the ribs, stabilizes the shoulder. The trigger point of the muscle contributes to the pain in front of the shoulder that could radiate to the chest, upper arms and all the way down to the inner side of the forearm.

Why can you feel the pain?

Pain receptors

Pain is a signal that is transmitted from the injured part of the body to the brain. Most illness causes pain; therefore the pain signal cannot be ignored. Noxious stimuli elicit tissue damage and activated pain receptors. Activation of pain receptors initiates the process that pain is experienced. Pain receptors are free nerve endings presented in the skin, muscles, joints, bone and viscera. They are sensory receptors that sense and detect tissue damage and then transmit the signal through nerves to the brain. There are three types of pain receptors. First type is skin pain receptors which are in the skin. They can sense pinching, cutting, stretching, temperature, chemicals and other mechanical. If the stimulation is prolonged, these receptors are sensitized and respond more widely. Second type is joint receptors in the joint capsules and ligaments. Third type is visceral pain receptors located in internal organs. Silent pain receptors or sleep pain receptors are these receptors that are normally not responding to noxious mechanical stimulation, however they can become responding to mechanical stimulation (They are awakened and no longer sleep any more) during inflammation and after tissue injury. This is because continuous stimulation from the damaged tissue reduces the threshold of these receptors and causes them to be responding again.

Pain receptors respond as soon as the tissues are damaged regardless the causes. Damaged tissues release substances from lysed cells and newly synthesized inflammatory substances at the site of injury such as globulin and protein kinase, arachidonic acid, histamine, nerve growth factors, substance P, potassium, 5HT and acetylcholine, lactic acid etc. Release of these substances reduces the threshold of the pain receptors and this is so called sensitization. If the receptors are sensitised, low level stimulation which was harmless in origin and did not cause any response before tissue damage can activate the pain receptors causing pain sensation. The response is rapid within 15-30 seconds after injury. The redness appears around the injury site caused by vasodilation and this inflammatory response becomes maximal after 5-10 minutes. Lowered pain threshold is seen in the area.

The pain cycle, what is involved?

Pain starts from activation of the nervous system. There are 9 steps of the pain circle:

Step 1: Local inflammation. Anything causing tissue damage such as injury, surgery, or infection can lead to local inflammation. This is the origin of the pain.

Step2: Peripheral sensitization. Local inflammation irritates the nerves lowering the pain threshold causing peripheral sensitization.

Step3: Central sensitization. Nerve signals are transmitted to the brain causing central sensitization.

Step4: Pain sensation. The brain tells you that there is pain in the body somewhere.

Step5: Pain cognitive processes. The brain where is sensing the pain connects other part of the brain where controls emotion causing emotional and behaviour changes.

Step6: Depression and anxiety. The brain where controls emotions is affected by the pain signals and alters its function causing depression and anxiety

Step7: Cortical reorganization. The brain reallocates its task to different parts of the body to reduce pain sensation and help replace the lost function.

Step8: Avoidance and disability. The body will respond the brain demands to redistribute the work causing avoidance and disabililty.

Step9: Muscle spasm deconditioning. Injured and related muscles become spasmed to protect the body from moving and feeling the pain causing muscle waste.

Pain and acupuncture.

Pain is an unpleasant feeling and a signal in the nervous system that something may be wrong. Pain could be in one area of the body, such as back pain or all over the body such as fibromyalgia.

It could be divided into two types of pain according to the onset and duration.
There are two types of pain: acute and chronic
Acute pain usually comes on suddenly, because of a disease, injury, or inflammation. It can often be diagnosed and treated. It usually goes away, though sometimes it can turn into chronic pain.
Chronic pain lasts for a long time, and can cause severe problems.

There are mainly three types of pain sensations
Pricking pain is caused by a needle, pin prick, skin cut etc. This type of pain is precisely localized from the skin and conducted by the A fibers of the nerves. It is sharp, fast and short duration in nature. This pain is a protection mechanism to the body and warning to the brain that something goes wrong.

Burning or soreness pain is caused by inflammation, burned skin etc. This type of pain is not exact localized and conducted by the C fibers of the nerves. It is characterised as diffuse, slow onset and longer in duration.

Aching pain is a sore pain which is mainly from the viscera and somatic deep structure. It is not precisely localized and carried by the C fibers of the nerves.

There are many ways to release pain. Acupuncture is one of the many treatments for pain relief and it is very efficient.  

Do you know anything about connection among pain, endorphins and acupuncture

Endorphins are neurotransmitters produced in the brain known as endogenous opioids and they can be found in the pituitary gland, in other parts of the brain, or distributed throughout the nervous system. They transmit electrical signals within the nervous system by interacting with opiate receptors in the brain. The action is similar to morphine and codeine, but without addiction or dependence. At least 20 types of endorphins have been found in humans. In response to pain and stress, they decrease feelings of pain and also lead to feelings of euphoria, modulate appetite, release sex hormones, and enhance the immune response. As a result, it makes people feel less pain and less stressed.

Many studies in animals and humans have demonstrated that acupuncture can cause multiple biological responses. Endorphins are released during acupuncture and that the analgesic effects of acupuncture are at least partially explained by their actions. That opioid antagonists such as naloxone reverse the analgesic effects of acupuncture further strengthens this hypothesis.