Osteolysis is an active resorption of bone matrix by osteoclasts and can be interpreted as the reverse of ossification. Although osteoclasts are active during the natural formation of healthy bone the term "osteolysis" specifically refers to a pathological process. Osteolysis often occurs in the proximity of a prosthesis that causes either an immunological response or changes in the bone's structural load. Osteolysis may also be caused by pathologies like bone tumors, cysts, or chronic inflammation.

In orthopedic medicine, fractures are classified in various ways. Historically they are named after the physician who first described the fracture conditions, however, there are more systematic classifications in place currently.

Even though symptoms vary widely after experiencing a bone fracture, the most common fracture symptoms include:

- pain in the fractured area

- swelling in the fractured area

- obvious deformity in the fractured area

- not being able to use or move the fractured area in a normal manner

- bruising, warmth, or redness in the fractured area

Distal clavicular osteolysis (DCO) is often associated with problems weightlifters have with their acromioclavicular joints due to high stresses put on the clavicle as it meets with the acromion. This condition is often referred to as "weight lifter's shoulder". Medical ultrasonography readily depicts resorption of the distal clavicle as irregular cortical erosions, whereas the acromion remains intact. Associated findings may include distended joint capsule, soft-tissue swelling, and joint instability.

A common surgery to treat recalcitrant DCO is re-sectioning of the distal clavicle, removing a few millimetres of bone from the very end of the bone.

A bone fracture (sometimes abbreviated FRX or Fx, F, or #) is a medical condition in which there is a damage in the continuity of the bone. A bone fracture may be the result of high force impact or stress, or a minimal trauma injury as a result of certain medical conditions that weaken the bones, such as osteoporosis, bone cancer, or osteogenesis imperfecta, where the fracture is then properly termed a pathologic fracture.

A "corner fracture" or "bucket-handle fracture" is fragmentation of the distal end of one or both femurs, with the loose piece appearing at the bone margins as an osseous density paralleling the metaphysis. The term "bucket-handle fracture" is used where the loose bone is rather wide at the distal end, making it end in a crescent shape. These types of fractures are characteristic of child abuse-related injuries.

Pycnodysostosis causes the bones to be abnormally dense (osteopetrosis); the last bones of the fingers (the distal phalanges) to be unusually short; and delays the normal closure of the connections (sutures) of the skull bones in infancy, so that the "soft spot" (fontanelle) on top of the head remains widely open.

Those with the syndrome have brittle bones which easily break, especially in the legs and feet. The jaw and collar bone (clavicle) are also particularly prone to fractures.

Other abnormalities involve the head and face, teeth, collar bones, skin, and nails. The front and back of the head are prominent. Within the open sutures of the skull, there may be many small bones (called wormian bones). The midface is less full than usual. The nose is prominent. The jaw can be small. The palate is narrow and grooved. The baby teeth are late coming in and may be lost much later than usual. The permanent teeth can also be slow to appear. The permanent teeth are commonly irregular and teeth may be missing (hypodontia). The collar bones are often underdeveloped and malformed. The skin over the back of the fingers is very wrinkled. The nails are flat and grooved.

Pycnodysostosis also causes problems that may become evident with time. Aside from the broken bones, the distal phalanges and the collar bone can undergo slow progressive deterioration. Vertebral defects may permit the spine to curve laterally resulting in scoliosis. The dental problems often require orthodontic care and cavities are common.

A clavicle fracture, also known as a broken collarbone, is a bone fracture of the clavicle. Symptoms typically include pain at the site of the break and a decreased ability to move the affected arm. Complications can include a collection of air in the pleural space surrounding the lung (pneumothorax), injury to the nerves or blood vessels in the area, and an unpleasant appearance.

It is often caused by a fall onto a shoulder, outstretched arm, or direct trauma. The fracture can also occur in a baby during childbirth. The middle section of the clavicle is most often involved. Diagnosis is typically based on symptoms and confirmed with X-rays.

Clavicle fractures are typically treated by putting the arm in a sling for one or two weeks. Pain medication such as paracetamol (acetaminophen) may be useful. It can take up to five months for the strength of the bone to return to normal. Reasons for surgical repair include an open fracture, involvement of the nerves or blood vessels, or shortening of the clavicle by more than 1.5 cm in a young person.

Clavicle fractures most commonly occur in people under the age of 25 and those over the age of 70. Among the younger group males are more often affected than females. In adults they make up about 5% of all fractures while in children they represent about 13% of fractures.

As with other types of fractures, scapular fracture may be associated with pain localized to the area of the fracture, tenderness, swelling, and crepitus (the crunching sound of bone ends grinding together). Since scapular fractures impair the motion of the shoulder, a person with a scapular fracture has a reduced ability to move the shoulder joint. Signs and symptoms may be masked by other injuries that accompany the scapular fracture.

The most common symptoms in impingement syndrome are pain, weakness and a loss of movement at the affected shoulder. The pain is often worsened by shoulder overhead movement and may occur at night, especially if the patient is lying on the affected shoulder. The onset of the pain may be acute if it is due to an injury or may be insidious if it is due to a gradual process such as an osteoarthritic spur. The pain has been described as dull rather than sharp, and lingers for long periods of a time, making it hard to fall asleep at night. Other symptoms can include a grinding or popping sensation during movement of the shoulder.

The range of motion at the shoulder may be limited by pain. A painful arc of movement may be present during forward elevation of the arm from 60° to 120°. Passive movement at the shoulder will appear painful when a downwards force is applied at the acromion but the pain will ease once the downwards force is removed.

A scapular fracture is a fracture of the scapula, the shoulder blade. The scapula is sturdy and located in a protected place, so it rarely breaks. When it does, it is an indication that the individual was subjected to a considerable amount of force and that severe chest trauma may be present. High-speed vehicle accidents are the most common cause. This could be anywhere from a car accident, motorcycle crash, or high speed bicycle crash but falls and blows to the area can also be responsible for the injury. Signs and symptoms are similar to those of other fractures: they include pain, tenderness, and reduced motion of the affected area although symptoms can take a couple of days to appear. Imaging techniques such as X-ray are used to diagnose scapular fracture, but the injury may not be noticed in part because it is so frequently accompanied by other, severe injuries that demand attention. The injuries that usually accompany scapular fracture generally have the greatest impact on the patient's outcome. However, the injury can also occur by itself; when it does, it does not present a significant threat to life. Treatment involves pain control and immobilizing the affected area, and, later, physical therapy.

Shoulder problems including pain, are one of the more common reasons for physician visits for musculoskeletal symptoms. The shoulder is the most movable joint in the body. However, it is an unstable joint because of the range of motion allowed. This instability increases the likelihood of joint injury, often leading to a degenerative process in which tissues break down and no longer function well.

Shoulder pain may be localized or may be referred to areas around the shoulder or down the arm. Other regions within the body (such as gallbladder, liver, or heart disease, or disease of the cervical spine of the neck) also may generate pain that the brain may interpret as arising from the shoulder.

Shoulder impingement syndrome, also called subacromial impingement, painful arc syndrome, supraspinatus syndrome, swimmer's shoulder, and thrower's shoulder, is a clinical syndrome which occurs when the tendons of the rotator cuff muscles become irritated and inflamed as they pass through the subacromial space, the passage beneath the acromion. This can result in pain, weakness and loss of movement at the shoulder.

As the name implies, movement of the shoulder is severely restricted in people with a "frozen shoulder". This condition, which doctors call adhesive capsulitis, is frequently caused by injury that leads to lack of use due to pain. Rheumatic disease progression and recent shoulder surgery can also cause frozen shoulder. Intermittent periods of use may cause inflammation. Adhesions (abnormal bands of tissue) grow between the joint surfaces, restricting motion. There is also a lack of synovial fluid, which normally lubricates the gap between the arm bone and socket to help the shoulder joint move. It is this restricted space between the capsule and ball of the humerus that distinguishes adhesive capsulitis from a less complicated painful, stiff shoulder. People with diabetes, stroke, lung disease, rheumatoid arthritis, and heart disease, or who have been in an accident, are at a higher risk for frozen shoulder. The condition rarely appears in people under the age of 40.

Pycnodysostosis (from Greek: πυκνός (puknos) meaning "dense", "dys" ("defective"), and "ostosis" ("condition of the bone")), is a lysosomal storage disease of the bone caused by a mutation in the gene that codes the enzyme cathepsin K.

An affected infant typically has the following triad of signs and symptoms: soft-tissue swelling, bone lesions, and irritability. The swelling occurs suddenly, is deep, firm, and may be tender. Lesions are often asymmetric and may affect several parts of the body. Affected bones have included the mandible, tibia, ulna, clavicle, scapula, ribs, humerus, femur, fibula, skull, ilium, and metatarsals. When the mandible (lower jaw bone) is affected, infants may refuse to eat, leading to failure to thrive.

The afflicted may have relatively small amounts of pain that will quickly increase in severity over a time period of 6–12 weeks. The skin temperature around the bone may increase, a bony swelling may be evident, and movement may be restricted in adjacent joints.

Spinal lesions may cause quadriplegia and patients with skull lesions may have headaches.

Commonly affected sites are metaphyses of vertebra, flat bones, femur and tibia. Approximate percentages by sites are as shown:

- Skull and mandible (4%)

- Spine (16%)

- Clavicle and ribs (5%)

- Upper extremity (21%)

- Pelvis and sacrum (12%)

- Femur (13%)

- Lower leg (24%)

- Foot (3%)

The basic method to check for a clavicle fracture is by an X-ray of the clavicle to determine the fracture type and extent of injury. In former times, X-rays were taken of both clavicle bones for comparison purposes. Due to the curved shape in a tilted plane X-rays are typically oriented with ~15° upwards facing tilt from the front. In more severe cases, a computerized tomography (CT) or magnetic resonance imaging (MRI) scan is taken.

However, the standard method of diagnosis through ultrasound imaging performed in the emergency room may be equally accurate in children.

Infantile cortical hyperostosis is a self-limited inflammatory disorder of infants that causes bone changes, soft tissue swelling and irritability. The disease may be present at birth or occur shortly thereafter. The cause is unknown. Both familial and sporadic forms occur. It is also known as Caffey disease or Caffey's disease.

Injury of the thoracic aorta refers to any injury which affects the portion of the aorta which lies within the chest cavity. Injuries of the thoracic aorta are usually the result of physical trauma; however, they can also be the result of a pathological process. The main causes of this injury are deceleration (such as a car accident) and crush injuries.

A brachial plexus injury (BPI), also known as brachial plexus lesion, is an injury to the brachial plexus, the network of nerves that conducts signals from the spinal cord to the shoulder, arm and hand. These nerves originate in the fifth, sixth, seventh and eighth cervical (C5–C8), and first thoracic (T1) spinal nerves, and innervate the muscles and skin of the chest, shoulder, arm and hand.

Brachial plexus injuries can occur as a result of shoulder trauma, tumours, or inflammation. The rare Parsonage-Turner Syndrome causes brachial plexus inflammation without obvious injury, but with nevertheless disabling symptoms. But in general, brachial plexus injury can be classified as either traumatic or obstetric. Obstetric injuries may occur from mechanical injury involving shoulder dystocia during difficult childbirth. Traumatic injury may arise from several causes. "The brachial plexus may be injured by falls from a height on to the side of the head and shoulder, whereby the nerves of the plexus are violently stretched...The brachial plexus may also be injured by direct violence or gunshot wounds, by violent traction on the arm, or by efforts at reducing a dislocation of the shoulder joint".

Signs and symptoms may include a limp or paralyzed arm, lack of muscle control in the arm, hand, or wrist, and lack of feeling or sensation in the arm or hand. Although several mechanisms account for brachial plexus injuries, the most common is nerve compression or stretch. Infants, in particular, may suffer brachial plexus injuries during delivery and these present with typical patterns of weakness, depending on which portion of the brachial plexus is involved. The most severe form of injury is nerve root avulsion, which usually accompanies high-velocity impacts that commonly occur during motor-vehicle collisions or bicycle accidents.

Torticollis is a fixed or dynamic tilt, rotation, with flexion or extension of the head and/or neck.

The type of torticollis can be described depending on the positions of the head and neck.

- laterocollis : the head is tipped toward the shoulder

- rotational torticollis : the head rotates along the longitudal axis

- anterocollis : forward flexion of the head and neck

- retrocollis : hyperextension of head and neck backward

A combination of these movements may often be observed. Torticollis can be a disorder in itself as well as a symptom in other conditions.

Other symptoms include:

- Neck pain

- Occasional formation of a mass

- Thickened or tight sternocleidomastoid muscle

- Tenderness on the cervical spine

- Tremor in head

- Unequal shoulder heights

- Decreased neck movement

There are inconsistencies in the terminology of aortic injury. There are several terms which are interchangeably used to describe injury to the aorta such as "tear", "laceration", "transection", and "rupture". "Laceration" is used as a term for the consequence of a tear, whereas a "transection" is a section across an axis or cross section. For all intents and purposes, the latter is used when a tear occurs across all or nearly all of the circumference of the aorta. "Rupture" is defined as a forcible disruption of tissue. Some disagree with the usage of "rupture" as they believe it implies that a tear is incompatible with life; however, the term accurately gauges the severity of tears in the aorta. A rupture can be either complete or partial, and can be classified further by the position of the tear.