Common symptoms include hip, knee (hip pathology can refer pain to a normal knee), or groin pain, exacerbated by hip or leg movement, especially internal hip rotation (with the knee flexed 90°, twisting the lower leg away from the center of the body). The range of motion is reduced, particularly in abduction and internal rotation, and the patient presents with a limp. Pain is usually mild. Atrophy of thigh muscles may occur from disuse and an inequality of leg length. In some cases, some activity can cause severe irritation or inflammation of the damaged area, including standing, walking, running, kneeling, or stooping repeatedly for an extended period of time. In cases exhibiting severe femoral osteonecrosis, pain is usually a chronic, throbbing sensation exacerbated by activity.

The first signs are complaints of soreness from the child, which are often dismissed as growing pains, and limping or other guarding of the joint, particularly when tired. The pain is usually in the hip, but can also be felt in the knee (referred pain). In some cases, pain is felt in the unaffected hip and leg, due to the children favoring their injured side and placing the majority of their weight on their "good" leg. It is predominantly a disease of boys (4:1 ratio). Perthes is generally diagnosed between 5 and 12 years of age, although it has been diagnosed as early as 18 months. Typically, the disease is only seen in one hip, but bilateral Perthes is seen in about 10% of children diagnosed.

Usually, a SCFE causes groin pain, but it may cause pain in only the thigh or knee, because the pain may be referred along the distribution of the obturator nerve. The pain may occur on both sides of the body (bilaterally), as up to 40 percent of cases involve slippage on both sides. After a first SCFE, when a second SCFE occurs on the other side, it typically happens within one year after the first SCFE. About 20 percent of all cases include a SCFE on both sides at the time of presentation.

Signs of a SCFE include a waddling gait, decreased range of motion. Often the range of motion in the hip is restricted in internal rotation, abduction, and flexion. A person with a SCFE may prefer to hold their hip in flexion and external rotation.

Failure to treat a SCFE may lead to: death of bone tissue in the femoral head (avascular necrosis), degenerative hip disease (hip osteoarthritis), gait abnormalities and chronic pain. SCFE is associated with a greater risk of arthritis of the hip joint later in life. 17-47 percent of acute cases of SCFE lead to the death of bone tissue (osteonecrosis) effects.

In many cases there is pain and discomfort in a joint which increases over time. While it can affect any bone, about half of cases show multiple sites of damage. Avascular necrosis primarily affects the joints at the shoulder, knee, and hip. The classical sites are: head of femur, neck of talus and waist of the scaphoid.

Avascular necrosis most commonly affects the ends of long bones such as the femur (the bone extending from the knee joint to the hip joint). Other common sites include the humerus (the bone of the upper arm), knees, shoulders, ankles and the jaw.

The classic clinical presentation of a hip fracture is an elderly patient who sustained a low-energy fall and now has groin pain and is unable to bear weight. Pain may be referred to the supracondylar knee. On examination, the affected extremity is often shortened and unnaturally, externally rotated compared to the unaffected leg.

Legg–Calvé–Perthes disease (LCPD, also known as Perthes disease or Legg–Perthes disease) is a childhood hip disorder initiated by a disruption of blood flow to the head of the femur. Due to the lack of blood flow, the bone dies (osteonecrosis or avascular necrosis) and stops growing. Over time, healing occurs by new blood vessels infiltrating the dead bone and removing the necrotic bone which leads to a loss of bone mass and a weakening of the femoral head. The bone loss leads to some degree of collapse and deformity of the femoral head and sometimes secondary changes to the shape of the hip socket. It is also referred to as idiopathic avascular osteonecrosis of the capital femoral epiphysis of the femoral head since the cause of the interruption of the blood supply of the head of the femur in the hip joint is unknown.

The condition is most commonly found in children between the ages of 4 and 8, but it can occur in children between the ages of 2 and 15. The main long-term problem with this condition is that it can produce a permanent deformity of the femoral head, which increases the risk of developing osteoarthritis in adults. Perthes is a form of osteochondritis which only affects the hip, although other forms of osteochondritis can affect elbows, knees, ankles, and feet. Bilateral Perthes, which means both hips are affected, should always be investigated thoroughly to rule out multiple epiphyseal dysplasia.

Fractures are commonly obvious, since femoral fractures are often caused by high energy trauma. Signs of fracture include swelling, deformity, and shortening of the leg. Extensive soft-tissue injury, bleeding, and shock are common. The most common symptom is severe pain, which prevents movement of the leg.

In osteochondritis dissecans, fragments of cartilage or bone become loose within a joint, leading to pain and inflammation. These fragments are sometimes referred to as joint mice. OCD is a type of osteochondrosis in which a lesion has formed within the cartilage layer itself, giving rise to secondary inflammation. OCD most commonly affects the knee, although it can affect other joints such as the ankle or the elbow.

People with OCD report activity-related pain that develops gradually. Individual complaints usually consist of mechanical symptoms including pain, swelling, catching, locking, popping noises, and buckling / giving way; the primary presenting symptom may be a restriction in the range of movement. Symptoms typically present within the initial weeks of stage I; however, the onset of stage II occurs within months and offers little time for diagnosis. The disease progresses rapidly beyond stage II, as OCD lesions quickly move from stable cysts or fissures to unstable fragments. Non-specific symptoms, caused by similar injuries such as sprains and strains, can delay a definitive diagnosis.

Physical examination typically reveals fluid in the joint, tenderness, and crepitus. The tenderness may initially spread, but often reverts to a well-defined focal point as the lesion progresses. Just as OCD shares symptoms with common maladies, acute osteochondral fracture has a similar presentation with tenderness in the affected joint, but is usually associated with a fatty hemarthrosis. Although there is no significant pathologic gait or characteristic alignment abnormality associated with OCD, the patient may walk with the involved leg externally rotated in an attempt to avoid tibial spine impingement on the lateral aspect of the medial condyle of the femur.

Femoral shaft fractures can be classified with the Winquist and Hansen classification, which is based on the amount of comminution.

The diagnosis is made by x-ray/MRI appearance and has five juxta-articular classifications and forehead, neck, and shaft classifications indicating early radiological signs.

Early on there is flattening of articular surfaces, thinning of cartilage with osteophyte (spur) formation. In juxta-articular lesions without symptoms, there is dead bone and marrow separated from living bone by a line of dense collagen. Microscopic cysts form, fill with necrotic material and there is massive necrosis with replacement by cancellous bone with collapse of the lesions.

The lesion begins as a random finding on x-ray without symptoms. Symptomatic lesions usually involve joint surfaces, and fracture with attempted healing occurs. This process takes place over months to years and eventually causes disabling arthritis, particularly of the femoral head (hip).

The following staging system is sometimes useful when managing lesions.

- Stage 0 - Intravascular coagulation

- Stage 1 - Dead Bone without repair

- Stage 2 - Dead Bone with repair but without collapse

- Stage 3 - Dead Bone with repair and with collapse

- Stage 4 - Secondary degenerative arthritis

In a study of bone lesions in 281 compressed air workers done by Walder in 1969, 29% of the lesions were in the humeral head (shoulder), 16% in the femoral head (hip), 40% in the lower end of the femur (lower thigh at the knee) and 15% in the upper tibia (knee below the knee cap).

Worsening of the condition from continued decompression in an asymptomatic x-ray finding may occur.

Dysbaric osteonecrosis or DON is a form of avascular necrosis where there is death of a portion of the bone that is thought to be caused by nitrogen embolism (blockage of the blood vessels by a bubble of nitrogen coming out of solution) in divers. Although the definitive pathologic process is poorly understood, there are several hypotheses:

- Intra- or extravascular nitrogen in bones, "nitrogen embolism".

- Osmotic gas effects due to intramedullary pressure effects.

- fat embolism

- hemoconcentration and increased coagulability.

Avascular necrosis (AVN), also called osteonecrosis or bone infarction, is death of bone tissue due to interruption of the blood supply. Early on there may be no symptoms. Gradually joint pain may develop which may limit the ability to move. Complication may include collapse of the bone or nearby joint surface.

Risk factors include bone fractures, joint dislocations, alcoholism, and the use of high dose steroids. The condition may also occur without any clear reason. The most commonly affected bone is the femur. Other relatively common sites include the upper arm bone, knee, shoulder, and ankle. Diagnosis is typically by medical imaging such as X-ray, CT scan, or MRI. Rarely biopsy may be used.

Treatments may include medication, not walking on the affected leg, stretching, and surgery. Most of the time surgery is eventually required and may include core decompression, osteotomy, bone grafts, or joint replacement. About 15,000 cases occur per year in the United States. People 30 to 50 years old are most commonly affected. Males are more commonly affected than females.

Fractures of the acetabulum occur when the head of the femur is driven into the pelvis. This injury is caused by a blow to either the side or front of the knee and often occurs as a dashboard injury accompanied by a fracture of the femur.

The acetabulum is a cavity situated on the outer surface of the hip bone, also called the coxal bone or innominate bone. It is made up of three bones, the ilium, ischium, and pubis. Together, the acetabulum and head of the femur form the hip joint.

Fractures of the acetabulum in young individuals usually result from a high energy injury like vehicular accident or feet first fall. In older individuals or those with osteoporosis, a trivial fall may result in acetabular fracture.

In 1964, French surgeons Robertt Judet, Jean Judet, and Emile Letournel first described the mechanism, classification, and treatment of acetabular fracture. They classified these fractures into elementary (simple two part) and associated (complex three or more part) fractures.

Coxa valga is a deformity of the hip where the angle formed between the head and neck of the femur and its shaft is increased, usually above 135 degrees. It is caused by a slipped epiphysis of the femoral head.

The differential diagnosis includes neuromuscular disorders (i.e. cerebral palsy, spinal dysraphism, poliomyelitis), skeletal dysplasias, and juvenile idiopathic arthritis.

Many people are unwell before breaking a hip; it is common for the break to have been caused by a fall due to some illness, especially in the elderly. Nevertheless, the stress of the injury, and a likely surgery, increases the risk of medical illness including heart attack, stroke, and chest infection.

Hip fracture patients are at considerable risk for thromboemoblism, blood clots that dislodge and travel in the bloodstream. Deep venous thrombosis (DVT) is when the blood in the leg veins clots and causes pain and swelling. This is very common after hip fracture as the circulation is stagnant and the blood is hypercoagulable as a response to injury. DVT can occur without causing symptoms. A pulmonary embolism (PE) occurs when clotted blood from a DVT comes loose from the leg veins and passes up to the lungs. Circulation to parts of the lungs are cut off which can be very dangerous. Fatal PE may have an incidence of 2% after hip fracture and may contribute to illness and mortality in other cases.

Mental confusion is extremely common following a hip fracture. It usually clears completely, but the disorienting experience of pain, immobility, loss of independence, moving to a strange place, surgery, and drugs combine to cause delirium or accentuate pre-existing dementia.

Urinary tract infection (UTI) can occur. Patients are immobilized and in bed for many days; they are frequently catheterised, commonly causing infection.

Prolonged immobilization and difficulty moving make it hard to avoid pressure sores on the sacrum and heels of patients with hip fractures. Whenever possible, early mobilization is advocated; otherwise, alternating pressure mattresses should be used.

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.

Coxa vara is a deformity of the hip, whereby the angle between the head and the shaft of the femur is reduced to less than 120 degrees. This results in the leg being shortened, and the development of a limp. It is commonly caused by injury, such as a fracture. It can also occur when the bone tissue in the neck of the femur is softer than normal, causing it to bend under the weight of the body. This may either be congenital or the result of a bone disorder. The most common cause of coxa vara is either congenital or developmental. Other common causes include metabolic bone diseases (e.g. Paget's disease of bone), post-Perthes deformity, osteomyelitis, and post traumatic (due to improper healing of a fracture between the greater and lesser trochanter). Shepherd's Crook deformity is a severe form of coxa vara where the proximal femur is severely deformed with a reduction in the neck shaft angle beyond 90 degrees. It is most commonly a sequela of osteogenesis imperfecta, Pagets disease, osteomyelitis, tumour and tumour-like conditions (e.g. fibrous dysplasia).

Coxa vara can happen in cleidocranial dysostosis.

Femoroacetabular Impingement (FAI), or hip impingement syndrome, may affect the hip joint in young and middle-aged adults and occurs when the ball shaped femoral head rubs abnormally or does not permit a normal range of motion in the acetabular socket. Damage can occur to the articular cartilage, or labral cartilage (soft tissue bumper of the socket), or both. Treatment options range from conservative to arthroscopic to open surgery.

Tibial plateau fractures typically presents with knee effusion, swelling of the knee soft tissues and inability to bear weight. The knee may be deformed due to displacement and/or fragmentation of the tibia which leads to loss of its normal structural appearance. Blood in the soft tissues and knee joint (hemarthrosis) may lead to bruising and a doughy feel of the knee joint. Due to the tibial plateau's proximity to important vascular (i.e. arteries, veins) and neurological (i.e. nerves such as peroneal and tibial) structures, injuries to these may occur upon fracture. A careful examination of the neurovascular systems is imperative. A serious complication of tibial plateau fractures is compartment syndrome in which swelling causes compression of the nerves and blood vessels inside the leg and may ultimately lead to necrosis or cell death of the leg tissues.

An intracapsular fracture is a bone fracture located within the joint capsule.

Examples of intracapsular fractures includes:

- In the hip: Fractures of the femoral head and femoral neck.

The condition is usually characterized by a sudden onset of knee pain, worse at night. Examination reveals tenderness of the medial femoral condyle, joint effusion, and occasional locking of the knee joint.

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.

The affected leg is virtually immovable by the patient, and is usually extremely painful. Dislocations are categorized as either posterior or anterior, based on the location of the head of the femur (see classification above).

Ideal x-ray visualization of an elementary fracture will depend on the fracture type:

- Posterior wall fracture: Iliac oblique and obturator oblique views

- Posterior column fracture: Iliac oblique and obturator oblique views

- Anterior wall fracture: Iliac oblique view

- Anterior column fracture: Obturator oblique view

In all cases, CT scan can assist in identifying impacted bone pieces, which may be found within the joint, and MRI may be done to identify the extent of potential injury to the sciatic nerve.

A Hoffa fracture is an intra-articular supracondylar distal femoral fracture, characterized by a fracture in the coronal plane.

It is named for Albert Hoffa.