There are several mechanisms of macro-trauma, including but not limited to:

1 A fall on an outstretched hand, which can produce a reflexive muscle contraction that tears the soft tissues around the joint. This force can jam the ball of the shoulder into the socket, and can be upwards, toward a side or into the socket.
2 A fall from a height onto a hard surface with a sudden stop, sometimes complicated by a twisting motion during the descent.
3 A sudden stop (the arm is stopped suddenly from its direction of movement), leading to failure in stretch (eccentric overload) and causing reflexive contraction of affected muscles / tendons to further increase the damage to the overloaded soft tissues in the shoulder.
4 A force-counterforce type of injury in which one force pushes one way and the shoulder has to pull or push the other way in order to maintain itself within the joint. This creates a shearing type of lesion to the soft tissues or articular cartilage of the joint.
5 A direct impact with an object such as a car, wall, seat, or the ground or floor (or a combination of more than one).
6 An incapacitating sports injury, whether contact or non-contact.

Injury Mechanism and Pathophysiology

Injuries to the shoulder can occur from trauma and/or overuse (daily life). In addition, general aging makes the shoulder susceptible to injury (not as resilient to the wear and tear of daily life). As one ages, it is common that there is a weaker inflammatory reaction and a diminished capacity to heal after injury.

Generally, an overuse injury comes from doing a specific task repeatedly, thus causing strain, bruising, tearing, and/or inflammation (repetitive micro-trauma). Examples include but are not limited to: carrying groceries, luggage, sporting equipment, and laundry; reaching overhead doing chores like painting or putting dishes/clothes away; household chores like sweeping, mopping, raking, or gardening; and sleeping on the side in an awkward position for a prolonged period of time. Activities at work can also cause overuse joint pain and dysfunction. Overuse coupled with poor conditioning and lack of endurance leads to fatigue failure of the tendons, ligament, or joint surface. The tired and worn-out tissues become torn and pain and inflammation ensues. If conservative measures fail and normal functioning does not return, then surgery will be recommended. Surgery can help stabilize torn tissues and remove scar tissue formations that have built up over time. If surgery is advised and the patient agrees, then surgery will be performed.

The other type of injury is a traumatic injury, which is caused by macro-trauma. A specific incident causes the person to stop what they are doing, secondary to pain or dysfunction. During macro-trauma, there are increased forces (commonly compression, shearing, and/or tensile) placed upon the shoulder. The person feels an immediate onset of pain and dysfunction in the shoulder.

In general, soft tissue or bone damage from macrotrauma can lead to increased bleeding within a joint and/or around a joint. During trauma to the shoulder it is common that the soft tissues (ligaments, tendons, muscles or connective tissues) get bruised, stretched, partially torn or completely torn. At times, the surrounding joints can get bruised, damaged, stretched out, or the tissues that hold the joint together (ligaments) can get torn. In addition, fractures (breaks) of the bones come from a traumatic event or from overuse. In the shoulder, they are the acromion, clavicle, or humerus bones.

After macro-trauma occurs, the damaged tissues bleed. The bodys reaction to damage creates inflammation. Essentially, the body brings in an excess of fluid (including but not limited to blood and cells) to help heal the damaged tissue. This bodily reaction leads to swelling, pain, and stiffness in an area of the body or around a joint. The result of inflammation within the soft tissue structures or joints can lead to scar tissue formation. Scar tissue is the body's attempt to heal damaged soft tissue structures. This is a normal reaction, but it can be very intense and lead to an overproduction of scar tissue formation, which in turn leads to narrowing, thickening, and/or extra bone formation (osteophytes or entheseophytes) around joints. The scar tissue can entrap small nerves around and within joints and can form "rubber bands" or "spider webs" within the joint. Therefore, with movement, the formed scar tissue can get stretched or pinched in the joint. The end result is a joint that is progressively more painful and dysfunctional. Many times, surgery to the joints is able to successfully remove excessive scar tissue, which offers pain relief and increased function.

No patient exactly follows a textbook. The reaction of the body to trauma is different for everyone. Everyone tolerates and perceives pain differently. The amount of scar tissue formed after trauma is different for different people. The injured person's tolerance of and progress at physical therapy are varied. With the passage of time and active physical therapy, if the patient fails to regain function and diminish pain, then surgery is warranted.

Many patients undergo surgery for two reasons: pain and the inability to perform the functional activities of daily living. These include but are not limited to: activities that are done daily, during recreational/sporting endeavors, and during work. The goal of surgery is to restore anatomy in an effort to increase function and to decrease pain. After micro- or macro-trauma, conservative measures can be undertaken at home, prior to undergoing surgical intervention.