**2. Anatomy of the musculoskeletal system**

The human musculoskeletal system (also known as the locomotor system) is a multiple organ system that gives human the ability to move using their muscles, tendons, and bones; it provides form, support, stability, and flexibility to the body as well as protecting vital organs [2]. Also, the skeletal portion of the system serves as the main storage system for calcium and phosphorus and contains critical components of the hematopoietic system [3].

Within the system, bones are connected to muscle fibers via connective tissue like tendons and ligaments. Muscles keep bones in place and also play a role in the movement of bones allowing overall motion; different bones are connected to by joints and cartilage prevents the bone ends from rubbing directly into each other.

There are, however, specific diseases and disorders, which will not be discussed in this chapter, that may adversely affect the function and overall effectiveness of the system. Some of which can be difficult to diagnose and treat in the emergency setting and may require a specialist to handle like an orthopedic surgeon; other issues may require physical rehabilitation which is handled by a physiotherapist.

**Figure 1.** Features of the human activity system from the 1911.

It is of worth to note that previously, the musculoskeletal system used to be called the activity system (**Figure 1**)*.*

#### **2.1. The skeleton**

seen in the emergency department. This requires the attending physician to have a thorough understanding of human anatomy and to be familiar with the subtypes of these injuries in order to prevent life- or limb-threatening damage, anticipate possible complications, and avoid further disability, any of which might not be clear from the immediate presentation of the injury. Patients may come to the emergency department with a variety of complaints and be in pain, but on examination are found to have a strain (tendon) or sprain (ligament). Many musculoskeletal injuries are overuse injuries resulting from strenuous and/or repetitive

Barring major complications and the potential for long-term deformities, most musculoskeletal injuries are relatively minor and rarely require an immediate life-threatening intervention. However, in patients who sustain blunt trauma, 85% incur musculoskeletal injuries that can be more serious. These patients need to be assessed and managed quickly and correctly. In cases of major musculoskeletal trauma when there are extraordinary forces that cause crushing injuries, the emergency physician may be confronted with more pressing challenges. When major muscle damage occurs, large amounts of myoglobin (a hemeprotein) are released into the bloodstream. When the myoglobin reaches the kidneys, it breaks down into harmful substances that can damage kidney cells, leading to precipitation in the renal tubules and acute kidney injury (AKI). Major musculoskeletal trauma can also result in internal torso injuries; in some cases, the pooling of fluids can form into an intact musculofascial layer with swelling in the space. This can cause complications such as acute compartment syndrome, which can lead to dire consequences if misdiagnosed. Continuous and careful assessment and correct recognition and management of musculoskeletal injuries in the emergency department are the key to successfully preventing further morbidity and reducing

The human musculoskeletal system (also known as the locomotor system) is a multiple organ system that gives human the ability to move using their muscles, tendons, and bones; it provides form, support, stability, and flexibility to the body as well as protecting vital organs [2]. Also, the skeletal portion of the system serves as the main storage system for calcium and

Within the system, bones are connected to muscle fibers via connective tissue like tendons and ligaments. Muscles keep bones in place and also play a role in the movement of bones allowing overall motion; different bones are connected to by joints and cartilage prevents the

There are, however, specific diseases and disorders, which will not be discussed in this chapter, that may adversely affect the function and overall effectiveness of the system. Some of which can be difficult to diagnose and treat in the emergency setting and may require a specialist to handle like an orthopedic surgeon; other issues may require physical rehabilitation

phosphorus and contains critical components of the hematopoietic system [3].

activity.

168 Essentials of Accident and Emergency Medicine

mortality.

**2. Anatomy of the musculoskeletal system**

bone ends from rubbing directly into each other.

which is handled by a physiotherapist.

This system serves many important functions; it aids in the shape and morphology of the whole body; it provides support and protection as well as allowing movement. It plays a major role in producing blood for the body and in storage of minerals [4]. The number of bones in the human skeleton is estimated to be around 270 at birth; however, many bones fuse together between birth and maturity. As a result, an average adult skeleton consists of 206 bones. The number of bones varies according to the method used to derive the count. While some consider certain structures to be a single bone with multiple parts, others may see it as a single part with multiple bones [5]. There are five general types of bones: long bones, short bones, flat bones, irregular bones, and sesamoid bones. The human skeleton is composed of both fused and individual bones. It is a complex structure with two distinct divisions; the axial skeleton, which includes the vertebral column, and the appendicular skeleton [2].

The skeletal system serves as a framework for tissues and organs to attach themselves to. This system acts as a protective structure for all vital organs. Major examples of this are the brain being protected by the skull and the heart with the lungs being protected by the rib cage.

Within the long bones are two distinctions of bone marrow (yellow and red). The yellow marrow has fatty connective tissue and is found in the marrow cavity. During starvation, the body uses the fat in yellow marrow for energy [2]. The red marrow of some bones is an important site for blood cell production; here, all erythrocytes, platelets, and most leukocytes form in adults. From the red marrow, erythrocytes, platelets, and leukocytes migrate to the peripheral blood to do their special tasks approximately 2.6 million red blood cells per second in order to replace existing cells that have been destroyed by the spleen [2].

Another function of bones is the storage of certain minerals. Calcium and phosphorus are among the main minerals being stored. The value of this storage "device" helps to regulate mineral balance in the bloodstream. When the fluctuation of minerals is high, these minerals are stored in bone; when it is low, it will be withdrawn from the bone.

### **2.2. Muscles**

There are three types of muscles (smooth, skeletal, and cardiac). Smooth muscles are nonstriated muscles used to control the flow of substances within the lumens of hollow organs like vessels and bowels and are involuntarily controlled [3]. Skeletal and cardiac muscles have striations that are visible under a microscope due to the components within their cells. Only skeletal and smooth muscles are part of the musculoskeletal system and only the skeletal muscles can move the body skeleton. Skeletal muscles are attached to bones and arranged in opposing groups around joints. Cardiac muscles are found in the heart only and used to pump blood; they are like the smooth muscles, involuntarily controlled. Muscles are innervated by nerves which conduct electrical currents from the central nervous system and cause the muscles to contract.

The body contains three types of muscle tissue seen under microscope as shown in (**Figure 2**): (a) skeletal muscle, (b) smooth muscle, and (c) cardiac muscle.

### **2.3. Joints**

Joints, also called articulations, serve two important functions in the human body: holding the skeleton together and allowing it to be mobile. Simply defined as the site where two or more bones meet [2].

There are three types of joints according to its functional classification which measures the amount of movement the joint provides: diarthrosis joints which allow extensive mobility between two or more articular heads; synarthrosis or false joints which are joints that do not provide mobility and amphiarthrosis joints which allow little or very minimal movement.

Cartilaginous joints are the joints where bone ends are tied by cartilage, and fibrous joints are the joints where the bone ends are united by fibrous tissue; the latter two types vary in mobil-

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A tendon is a tough, flexible band of fibrous connective tissue that connects muscles to bones [4]. The extracellular connective tissue between muscle fibers binds to tendons at the distal

ity according to their subclassifications and position in the body [2].

**2.4. Tendons**

**Figure 2.** Muscle tissue under microscope.

Structural classification is based on the type of the material binding the bones together. Synovial joints (**Figure 3**) are the joints where the bones are lubricated by a solution called synovial fluid that is produced by the synovial membranes. This fluid lowers the friction between the articular surfaces and is kept within an articular capsule allowing maximum mobility.

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Cartilaginous joints are the joints where bone ends are tied by cartilage, and fibrous joints are the joints where the bone ends are united by fibrous tissue; the latter two types vary in mobility according to their subclassifications and position in the body [2].

#### **2.4. Tendons**

Within the long bones are two distinctions of bone marrow (yellow and red). The yellow marrow has fatty connective tissue and is found in the marrow cavity. During starvation, the body uses the fat in yellow marrow for energy [2]. The red marrow of some bones is an important site for blood cell production; here, all erythrocytes, platelets, and most leukocytes form in adults. From the red marrow, erythrocytes, platelets, and leukocytes migrate to the peripheral blood to do their special tasks approximately 2.6 million red blood cells per second in order

Another function of bones is the storage of certain minerals. Calcium and phosphorus are among the main minerals being stored. The value of this storage "device" helps to regulate mineral balance in the bloodstream. When the fluctuation of minerals is high, these minerals

There are three types of muscles (smooth, skeletal, and cardiac). Smooth muscles are nonstriated muscles used to control the flow of substances within the lumens of hollow organs like vessels and bowels and are involuntarily controlled [3]. Skeletal and cardiac muscles have striations that are visible under a microscope due to the components within their cells. Only skeletal and smooth muscles are part of the musculoskeletal system and only the skeletal muscles can move the body skeleton. Skeletal muscles are attached to bones and arranged in opposing groups around joints. Cardiac muscles are found in the heart only and used to pump blood; they are like the smooth muscles, involuntarily controlled. Muscles are innervated by nerves which conduct electrical currents from the central nervous system and cause

The body contains three types of muscle tissue seen under microscope as shown in (**Figure 2**):

Joints, also called articulations, serve two important functions in the human body: holding the skeleton together and allowing it to be mobile. Simply defined as the site where two or more

There are three types of joints according to its functional classification which measures the amount of movement the joint provides: diarthrosis joints which allow extensive mobility between two or more articular heads; synarthrosis or false joints which are joints that do not provide mobility and amphiarthrosis joints which allow little or very minimal movement.

Structural classification is based on the type of the material binding the bones together. Synovial joints (**Figure 3**) are the joints where the bones are lubricated by a solution called synovial fluid that is produced by the synovial membranes. This fluid lowers the friction between the articular surfaces and is kept within an articular capsule allowing maximum

to replace existing cells that have been destroyed by the spleen [2].

are stored in bone; when it is low, it will be withdrawn from the bone.

(a) skeletal muscle, (b) smooth muscle, and (c) cardiac muscle.

**2.2. Muscles**

170 Essentials of Accident and Emergency Medicine

the muscles to contract.

**2.3. Joints**

mobility.

bones meet [2].

A tendon is a tough, flexible band of fibrous connective tissue that connects muscles to bones [4]. The extracellular connective tissue between muscle fibers binds to tendons at the distal

**3. Addressing musculoskeletal injuries**

ment for these injuries is based on simple four steps:

**1.** Inspection (discoloration, swelling, or deformity). **2.** Palpation (looking for tenderness and deformity).

This should cover the basic general approach of these injuries.

**4. Classification and management of musculoskeletal injuries**

1 This will include soft tissue and connective tissue injuries for the sake of simplification.

patient had and the timing of it.

below the injured part.

**4.1. Soft tissue injuries1**

*4.1.1. Closed wounds*

can be divided into:

**4.** Neurovascular examination.

It is valuable to have as much insight as possible about the incident, even the site of the incident, as any information may aid in weighing the level of trauma, things like the patient position, causative mechanism of injury (penetrating, blunt, crushing…), bleeding at the scene, exposed bone or fracture ends, open wounds, any deformity or dislocation, motor and/or sensory deficits, delays in transportation, limb function, perfusion, and neurological changes. Other things to keep in mind are to pay special attention to excessive pressure over prominences as they may result in a peripheral nerve compression, compartment syndromes, or crush syndromes. A thorough history is the first step; always ask about the mechanism of the trauma, it is very essential in the management of musculoskeletal injuries and then past medical history to assess any morbidities, history of medications, any previous injuries, and the last meal the

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Second in line is physical examination. The physical examination in the emergency depart-

**3.** Assess range of motion (both active and passive) with consideration to the joint above and

The soft tissue is a term that encompasses all body tissue except the bones. It includes skin, muscles, vessels, ligaments, tendons, and nerves. Their injuries can range from the trivial, such as a scraped knee, to the critical that includes internal bleeding; those which involve the skin and underlying musculature are commonly divided either as closed or open wounds.

An injury where there is no open pathway from the outside to the injured site (**Figure 4**) and

**Figure 3.** Anatomy of synovial joint.

and proximal ends, and the tendon binds to the periosteum of individual bones at the muscle's origin and insertion. As muscles contract, tendons transmit the forces to the relatively rigid bones, pulling on them and causing movement. Tendons can stretch substantially, allowing them to function as springs during locomotion, thereby saving energy.

#### **2.5. Ligaments**

A ligament is a small band of dense, white, fibrous elastic connective tissue [2] that connects both ends of bones together in order to form a joint and they transfer force from one bone to the other allowing movement [6]. Most ligaments limit dislocation or prevent certain movements that can cause injury or tears. Since they are elastic tissue, they increasingly lengthen when under pressure; when the force exceeds the limit of elasticity, the ligament can handle; it becomes susceptible to damage which can result in severe injuries and tears or in an unstable joint movement. Ligaments may also restrict some actions and movements such as hyperextension or hyperflexion that is limited by the ligament ability to prevent this movement to an extent [7].

#### **2.6. Bursa**

A bursa is a small synovial fluid-filled sac contained within white fibrous connective tissue which is lined internally with synovial membrane. It provides a cushion between bones and tendons and/or muscles around a joint. The fluid-filled sac can be found in multiple regions in the body mostly around joints [2].
