The shoulder is the most flexible joint in your body consisting of three bones namely humerus (upper arm), scapula (shoulder blade), and clavicle (collarbone). The top of the humerus is ball-shaped, and it fits into a shallow socket present in the scapula. The ligaments in the shoulder help to keep the ball centered in the socket while the rotator cuff muscles allow you to rotate and lift the arm. If this part of your body gets injured, then you can experience pain in the shoulder muscles.

Causes of shoulder muscle pain
Shoulder pain, also known as deltoid pain, is a common problem that people face due to a variety of reasons.

• Rotator cuff problem (outside the shoulder region)
  Altogether, there are four rotator cuff muscles present in the shoulder region that allow individuals to move the shoulder. These muscles are not involved while lifting heavy objects. The three causes of pain in the shoulder muscles associated with the rotator cuff are tendonitis, bursitis, and rotator cuff tear. While bursitis and tendonitis refer to an inflammation of the bursa and tendons, a rotator cuff tear generally occurs when the tendons get separated from the bone due to an injury.

Rotator cuff injuries are associated with symptoms that tend to become worse at night. It also leads to a painful sensation during physical activities such as reaching or throwing. Patients with a rotator cuff tear tend to suffer from loss of sleep because of the pain in the shoulder muscles. Sometimes, your muscles may feel stiff due to the injury or inflammation caused by a rotator cuff tear or tendonitis.

• Bicep tendonitis (Front of the shoulder region)
  Patients with this condition usually develop gradual pain at the front of the shoulder. It spreads over the length of the bicep muscles and gets worse with repetitive lifting, carrying heavy objects or overhead activities. People suffering from bicep tendonitis often experience that their symptoms flare up at night.
• AC arthritis (Top of the shoulder region)
  Shoulder arthritis is less common than knee and hip arthritis, but when it becomes severe, it may cause bone spurs and rough cartilage. All of this hinders the mobility of the shoulder. It may also require joint replacement surgery. Exposed bone and uneven cartilage surfaces may cause a grinding sensation, especially while reaching overhead or across the chest.
• Shoulder instability (All across the shoulder region)
  Shoulder instability refers to the condition responsible for producing loose joints. Most of the times, a traumatic injury or overused muscles cause this problem. Some people suffer from shoulder instability due to loose ligaments, and this is known as multidirectional instability. People often describe the symptoms of shoulder instability as “dead arm” due to the excessive range of shoulder motion. They also get a feeling that their shoulder will not stay in position or pop out of the joint.

Repercussions of pain in the shoulder muscle
Shoulder muscle pain can result in the following problems:

• Inability to carry objects
• Shoulder pain at night or while resting
• Difficulties in using or raising the arm
• Swelling or bruising around the shoulder joint or arm
• Sudden muscle cramps
• Neck pain or jaw pain

Treatment of shoulder muscle pain
The treatment of shoulder muscle pain depends entirely on the cause of the problem. Thus, it is of the utmost importance to seek appropriate medical advice so that you know the underlying cause and treatment options available to you. Some of the treatment procedures are as follows:

• Rest
  The first and foremost treatment method for shoulder muscle pain is to rest the joint and allow the acute inflammation to settle. While taking rest, one must remember that resting for prolonged durations may cause immobilization that can cause a frozen shoulder.
• Ice and heat application
  Ice packs are often used to reduce the swelling and pain caused by an acute shoulder injury. It is also used to treat shoulder overuse injuries to diminish the onset of any inflammation. On the other hand, heat pads can treat chronic shoulder conditions, but usually, it is used before performing any overhead activity as the heat relaxes the muscles, and reduces stiffness and pain.
• Physical activity
  Physical therapy is a crucial aspect that physical therapists focus on. They use different modalities to increase strength, restore mobility, and help patients return to their pre-injury level of activity.
• Surgical treatment methods
  In some cases, surgery may be necessary if the shoulder muscle pain worsens with time and if conservative treatment methods are not working. If your shoulder requires surgery, you must consult an orthopedic surgeon beforehand to treat the shoulder muscle pain.

Now that you know all about shoulder muscle pain, you can look at the symptoms, identify the causes, and seek a cure accordingly. However, a medical consultation is strongly recommended before proceeding with any line of treatment.