Hip dysplasia can range from barely detectable to severely malformed or dislocated.

The congenital form, teratologic or non-reducible dislocation occurs as part of more complex conditions.

The condition can be bilateral or unilateral:

- If both hip joints are affected one speaks of "bilateral" dysplasia. In this case some diagnostic indicators like asymmetric folds and leg-length inequality do not apply.

- In unilateral dysplasia only one joint shows deformity, the contralateral side may show resulting effects. In the majority of unilateral cases the left hip has the dysplasia.

If the joint is fully dislocated a false acetabulum often forms (often higher up on the pelvis) opposite the dislocated femoral head position.

In acetabular dysplasia the acetabulum (socket) is too shallow or deformed. The center-edge angle is measured as described by Wiberg. Two forms of femoral dysplasia are coxa vara, in which the femur head grows at too narrow an angle to the shaft, and coxa valga, in which the angle is too wide.

A rare type, the "Beukes familial hip dysplasia" is found among Afrikaners that are members of the Beukes family. The femur head is flat and irregular. People develop osteoarthritis at an early age.

Sprengel's deformity (also known as high scapula or congenital high scapula) is a rare congenital skeletal abnormality where a person has one shoulder blade that sits higher on the back than the other. The deformity is due to a failure in early fetal development where the shoulder fails to descend properly from the neck to its final position. The deformity is commonly associated with other conditions, most notably Klippel-Feil syndrome, congenital scoliosis including cervical scoliosis, fused ribs, the presence of an omovertebral bone and spina bifida. The left shoulder is the most commonly affected shoulder but the condition can be bilateral, meaning that both shoulders are affected. About 75% of all observed cases are girls. Treatment includes surgery in early childhood and physical therapy. Surgical treatment in adulthood is complicated by the risk of nerve damage when removing the omovertebral bone and when stretching the muscle tissue during relocation of the shoulder.

The scapula is small and rotated so that its inferior edge points toward the spine. There is a high correlation between Sprengel's deformity and the Klippel-Feil syndrome. Sometimes a bony connection is present between the elevated scapula and one of the cervical vertebrae, usually C5 or C6. This connection is known as the omovertebral bone.

Hip dysplasia is an abnormality of the hip joint where the socket portion does not fully cover the ball portion, resulting in an increased risk for joint dislocation. Hip dysplasia may occur at birth or develop in early life. Regardless, it does not typically produce symptoms in babies less than a year old. Occasionally one leg may be shorter than the other. The left hip is more often affected than the right. Complications without treatment can include arthritis, limping, and low back pain.

Risk factors for hip dysplasia include family history, certain swaddling practices, and breech birth. If one identical twin is affected, there is a 40% risk the other will also be affected. Screening all babies for the condition by physical examination is recommended. Ultrasonography may also be useful.

Many of those with mild instability resolve without specific treatment. In more significant cases, if detected early, bracing may be all that is required. In cases that are detected later, surgery and casting may be needed. About 7.5% of hip replacements are done to treat problems which have arisen from hip dysplasia.

About 1 in 1,000 babies have hip dysplasia. Hip instability of meaningful importance occurs in one to two percent of babies born at term. Females are affected more often than males. Hip dysplasia was described at least as early as the 300s BC by Hippocrates.

Synostosis (plural: synostoses) is fusion of two bones. It can be normal in puberty, fusion of the epiphysis, or abnormal. When synostosis is abnormal it is a type of dysostosis.

Examples of synostoses include:

- craniosynostosis – an abnormal fusion of two or more cranial bones;

- radioulnar synostosis – the abnormal fusion of the radius and ulna bones of the forearm;

- tarsal coalition – a failure to separately form all seven bones of the tarsus (the hind part of the foot) resulting in an amalgamation of two bones; and

- syndactyly – the abnormal fusion of neighboring digits.

Synostosis within joints can cause ankylosis.

Radioulnar synostosis is one of the more common failures of separation of parts of the upper limb. There are two general types: one is characterized by fusion of the radius and ulna at their proximal borders and the other is fused distal to the proximal radial epiphysis. Most cases are sporadic, congenital (due to a defect in longitudinal segmentation at the 7th week of development) and less often post-traumatic, bilateral in 60%, and more common in males. Familial cases in association with autosomal dominant transmission appear to be concentrated in certain geographic regions, such as Sicily.

The condition frequently is not noted until late childhood, as function may be normal, especially in unilateral cases. Increased wrist motion may compensate for the absent forearm motion. It has been suggested that individuals whose forearms are fixed in greater amounts of pronation (over 60 degrees) face more problems with function than those with around 20 degrees of fixation. Pain is generally not a problem, unless radial head dislocation should occur.

Most examples of radioulnar synostosis are isolated (non-syndromic). Syndromes that may be accompanied by radioulnar synostosis include X chromosome polyploidy (e.g., XXXY) and other chromosome disorders (e.g., 4p- syndrome, Williams syndrome), acrofacial dysostosis, Antley–Bixler syndrome, genitopatellar syndrome, Greig cephalopolysyndactyly syndrome, hereditary multiple osteochondromas (hereditary multiple exostoses), limb-body wall complex, and Nievergelt syndrome.

Craniosynostosis (from cranio, cranium; + syn, together; + ostosis relating to bone) is a condition in which one or more of the fibrous sutures in an infant skull prematurely fuses by turning into bone (ossification). Craniosynostosis has following kinds: scaphocephaly, trigonocephaly, plagiocephaly, anterior plagiocephaly, posterior plagiocephaly, brachycephaly, oxycephaly, pansynostosis.

Proximal femoral focal deficiency (PFFD), also known as Congenital Femoral Deficiency (CFD), is a rare, non-hereditary birth defect that affects the pelvis, particularly the hip bone, and the proximal femur. The disorder may affect one side or both, with the hip being deformed and the leg shortened.

It is commonly linked with the absence or shortening of a leg bone (fibular hemimelia) and the absence of a kneecap. Other linked birth defects include the dislocation or instability of the joint between the femur and the kneecap, a shortened tibia or fibula, and foot deformities.

There are typically four classes (or "types") of PFFD, ranging from class A to class D, as detailed by Aitken.

Radioulnar synostosis is a rare condition where there is an abnormal connection between the radius and ulna bones of the forearm. This can be present at birth (congenital), when it is a result of a failure of the bones to form separately, or following an injury (post-traumatic).

It typically causes restricted movement of the forearm, in particular rotation (pronation and supination), though is not usually painful unless it causes subluxation of the radial head. It can be associated with dislocation of the radial head which leads to limited elbow extension.

A Bankart lesion is an injury of the anterior (inferior) glenoid labrum of the shoulder due to anterior shoulder dislocation. When this happens, a pocket at the front of the glenoid forms that allows the humeral head to dislocate into it. It is an indication for surgery and often accompanied by a Hill-Sachs lesion, damage to the posterior humeral head.

The Bankart lesion is named after English orthopedic surgeon Arthur Sydney Blundell Bankart (1879 – 1951).

A bony Bankart is a Bankart lesion that includes a fracture in of the anterior-inferior glenoid cavity of the scapula bone.

It is a congenital subluxation or dislocation of the ulna's distal end, due to malformation of the bones. Sometimes, minor abnormalities of other bone structures, often caused by disease or injury, such as a fracture of the distal end of the radius with upward displacement of the distal fragment. The deformity varies in degree from a slight protrusion of the lower end of the ulna, to complete dislocation of the inferior radio-ulnar joint with marked radial deviation of the hand. Severe deformities are associated with congenital absence or hypoplasia of the radius.

The male:female rate of this disorder is 1:4. The incidence is unknown, and there is no described racial predominance. Even though Madelung's Deformity is considered a congenital disorder, symptoms sometimes aren't seen until adulthood. In most cases, symptoms find their onset during midchildhood. At this age, the relatively slower growth of the ulnar and palmar part of the radius, leads to an increasingly progressive deformity. Pain and deformity are the main symptoms patients present with. Typical clinical presentation consists of a short forearm, anterior-ulnar bow of the radius and a forward subluxation of the hand on the forearm. As mentioned before, the severity of the disorder varies greatly, which also leads to a spectrum of presentation.

Characteristics are:

- A fibrous band instead of the fibula

- Short deformed leg

- Absence of the lateral part of the ankle joint (due to absence of the distal end of the fibula), and what is left is unstable; the foot has an equinovalgus deformity

- Possible absence of part of the foot requiring surgical intervention to bring the foot into normal function, or amputation.

- Possible absence of one or two toes on the foot

- Possible conjoined toes or metatarsals

Partial or total absence of fibula is among the most frequent limb anomalies. It is the most common long bone deficiency and is the most common skeletal deformity in the leg. It most often is unilateral (present only on one side). It may also present as bilateral (affecting both legs). Paraxial fibular hemimelia is the most common manifestation in which only the postaxial portion of the limb is affected. It is commonly seen as a complete terminal deficiency, where the lateral rays of the foot are also affected. Hemimelia can also be intercalary in which case the foot remains unaffected. Although the missing bone is easily identified, this condition is not simply a missing bone. Males are affected twice as often as females in most series.

The symptoms can be numerous depending on the severity of the dislocation injury and how long the person is inflicted with the injury. Symptoms of a dislocated jaw include a bite that feels “off” or abnormal, hard time talking or moving jaw, not able to close mouth completely, drooling due to not being able to shut mouth completely, teeth feel they are out of alignment, and a pain that becomes unbearable

The immediate symptom can be a loud crunch noise occurring right up against the ear drum. This is instantly followed by excruciating pain, particularly in the side where the dislocation occurred.

Short-term symptoms can range from mild to chronic headaches, muscle tension or pain in the face, jaw and neck.

Long-term symptoms can result in sleep deprivation, tiredness/lethargy, frustration, bursts of anger or short fuse, difficulty performing everyday tasks, depression, social issues relating to difficulty talking, hearing sensitivity (particularly to high pitched sounds), tinnitus and pain when seated associated with posture while at a computer and reading books from general pressure on the jaw and facial muscles when tilting head down or up. And possible causing subsequent facial asymmetry.

In contrast, symptoms of a fractured jaw include bleeding coming from the mouth, unable to open the mouth wide without pain, bruising and swelling of the face, difficulty eating due to the constant pain, loss of feeling in the face (more specifically the lower lip) and lacks full range of motion of the jaw.

Individuals affected by ischiopatellar dysplasia commonly have abnormalities of the patella and pelvic girdle, such as absent or delayed patellar and ischial ossification as well as infra-acetabular axe-cut notches. Patellae are typically absent or small in these individuals, when patellae are present they are small and laterally displaced or dislocated. In addition, abnormalities in other parts of their skeleton and dysmorphic features are common in those affected. Other features that have been identified in patients with ischiopatellar dysplasia include foot anomalies, specifically flat feet (pes planus), syndactylism of the toes, short fourth and fifth toes, and a large gap between the first and second toes, femur anomalies, cleft palate, and craniofacial dysmorphisms.

Fibular hemimelia or longitudinal fibular deficiency is "the congenital absence of the fibula and it is the most common congenital absence of long bone of the extremities." It is the shortening of the fibula at birth, or the complete lack thereof. In humans, the disorder can be noted by ultrasound in utero to prepare for amputation after birth or complex bone lengthening surgery. The amputation usually takes place at six months with removal of portions of the legs to prepare them for prosthetic use. The other treatments which include repeated corrective osteotomies and leg-lengthening surgery (Ilizarov apparatus) are costly and associated with residual deformity.

Congenital radioulnar synostosis is rare, with approximately 350 cases reported in journals, and it typically affects both sides (bilateral) and can be associated with other skeletal problems such as hip and knee abnormalities, finger abnormalities (syndactyly or clinodactyly), or Madelung's deformity. It is sometimes part of known genetic syndromes such as triple X-Y (XXXY), Apert's, William's, or Holt-Oram. It has been reported to run in families typically following an autosomal dominant inheritance pattern which means children of an affected parent have a 50% chance of having the condition. When associated wth amegakaryocytic thrombocytopenia this inheritance has been found to be caused by mutations to the "HOXA11" gene.

The Monteggia fracture is a fracture of the proximal third of the ulna with dislocation of the proximal head of the radius. It is named after Giovanni Battista Monteggia.

In an anterior dislocation the limb is held by the patient in externally rotated with mild flexion and abduction. Femoral nerve palsies can be present, but are uncommon.

Nine out of ten hip dislocations are posterior. The affected limb will be in a position of flexion, adduction, and internally rotated in this case. The knee and the foot will be in towards the middle of the body. A sciatic nerve palsy is present in 8%-20% of cases.

Dislocations occur when two bones that originally met at the joint detach. Dislocations should not be confused with Subluxation. Subluxation is when the joint is still partially attached to the bone.

When a person has a dislocated jaw it is difficult to open and close the mouth. Dislocation can occur following a series of events if the jaw locks while open or unable to close. If the jaw is dislocated, it may cause an extreme headache or inability to concentrate. When the muscle's alignment is out of sync, a pain will occur due to unwanted rotation of the jaw.

If the pain remains constant, it may require surgery to realign the jaw. Depending on the severity of the jaw's dislocation, pain relief such as paracetamol may assist to alleviate the initial chronic pain. If the pain relief is taken for an extended period of time, it may negatively affect the person while talking, eating, drinking, etc.

Madelung's deformity is usually characterized by malformed wrists and wrist bones and is often associated with Léri-Weill dyschondrosteosis. It can be bilateral (in both wrists) or just in the one wrist.

It has only been recognized within the past hundred years.

Mechanisms include:

- Fall on an outstretched hand with the forearm in excessive pronation (hyper-pronation injury). The Ulna fractures in the proximal one-third of the shaft due to extreme dislocation. Depending on the impact and forces applied in each direction, degree of energy absorption determines pattern, involvement of the radial head and whether or not open soft tissue occurs.

- Direct blow on back of upper forearm would be a very uncommon cause. In this context, isolated ulnar shaft fractures are most commonly seen in defence against blunt trauma (e.g. nightstick injury). Such an isolated ulnar shaft fracture is "not" a Monteggia fracture. It is called a 'nightstick fracture'.

Chopart's fracture–dislocation is a dislocation of the mid-tarsal (talonavicular and calcaneocuboid) joints of the foot, often with associated fractures of the calcaneus, cuboid and navicular.

The Essex-Lopresti fracture is a fracture of the radial head with concomitant dislocation of the distal radio-ulnar joint and disruption of the interosseous membrane. The injury is named after Peter Essex-Lopresti who described it in 1951.

The injury can be difficult to diagnose initially as the attention is focused on the injury to the radial head, leading to the distal radio-ulnar injury being overlooked. The examination finding of tenderness of the distal radio-ulnar joint suggests an Essex-Lopresti injury in patients who have sustained high energy forearm trauma. Plain radiography shows the radial head fracture, with dorsal subluxation of the ulna often seen on lateral view of the pronated wrist.