Increased risk of developing knee and hip osteoarthritis was found in those who:

- work with manual handling (e.g. lifting)

- have physically demanding work

- walk at work

- have climbing tasks at work (e.g. climb stairs or ladders)

Increased risk of developing hip osteoarthritis over time was found among those who work in bent or twisted positions.

Increased risk of knee osteoarthritis was found in those who:

- work in a kneeling or squatting position

- experience heavy lifting in combination with a kneeling or squatting posture

- work standing up

A number of studies have shown that there is a greater prevalence of the disease among siblings and especially identical twins, indicating a hereditary basis. Although a single factor is not generally sufficient to cause the disease, about half of the variation in susceptibility has been assigned to genetic factors.

As early human ancestors evolved into bipeds, changes occurred in the pelvis, hip joint and spine which increased the risk of osteoarthritis. Additionally genetic variations that increase the risk were likely not selected against because usually problems only occur after reproductive success.

The development of osteoarthritis is correlated with a history of previous joint injury and with obesity, especially with respect to knees. Since the correlation with obesity has been observed not only for knees but also for non-weight bearing joints and the loss of body fat is more closely related to symptom relief than the loss of body weight, it has been suggested that there may be a metabolic link to body fat as opposed to just mechanical loading.

Changes in sex hormone levels may play a role in the development of osteoarthritis as it is more prevalent among post-menopausal women than among men of the same age. A study of mice found natural female hormones to be protective while injections of the male hormone dihydrotestosterone reduced protection.

55% of facet syndrome cases occur in cervical vertebrae, and 31% in lumbar. Facet syndrome can progress to spinal osteoarthritis, which is known as spondylosis. Pathology of the C1-C2 (atlantoaxial) joint, the most mobile of all vertebral segments, accounts for 4% of all spondylosis.

Like many other joints throughout the human body, facets can experience natural degeneration from constant use. Over time, the cartilage within the joints can naturally begin to wear out, allowing it to become thin or disappear entirely which, in turn, allows the conjoining vertebrae to rub directly against one another with little or no lubricant or separation. A result of this rubbing is often swelling, inflammation or other painful symptoms.

Over time, the body will naturally respond to the instability within the spine by developing bone spurs, thickened ligaments or even cysts that can press up against or pinch the sensitive nerve roots exiting the spinal column.

While primarily caused through natural wear and tear, advanced facet syndrome can also occur as a result of injury to the spine, degenerative disease or lifestyle choices. These causes can include:

- An unexpected, traumatic event such as a car accident, significant fall or high impact sports injury.

- Osteoarthritis

- Spondylolisthesis

- Obesity

- Smoking

- Malnutrition

- Lack of physical exercise or daily activity

Facet joint arthrosis is an intervertebral disc disorder. The facet joints or zygapophyseal joints are synovial cartilage covered joints that limit the movement of the spine and preserve segmental stability. In the event of hypertrophy of the vertebrae painful arthrosis can occur. The "lumbar facet arthrosis syndrome" was described in a 1987 article by S. M. Eisenstein and C. R. Parry of Witwatersrand University.

Computerized tomography is the ideal for typifying facet joint arthrosis; evidence suggests that magnetic resonance imaging is not reliable in this regard.

Causes of the swelling can include arthritis, injury to the ligaments of the knee, or an accident after which the body's natural reaction is to surround the knee with a protective fluid. There could also be an underlying disease or condition. The type of fluid that accumulates around the knee depends on the underlying disease, condition or type of traumatic injury that caused the excess fluid. The swelling can, in most cases, be easily cured.

Underlying diseases may include

- Knee osteoarthritis

- Rheumatoid arthritis

- Infection

- Gout

- Pseudogout

- Prepatellar bursitis (kneecap bursitis)

- Cysts

- Tumours

- Repetitive strain injury

Having osteoarthritis or engaging in high-risk sports that involve rapid cut-and-run movements of the knee — football or tennis, for example — means an individual is more likely to develop water on the knee.

In overweight or obese individuals the body places more weight on the knee joint. This causes more wear in the joint. Over time, the body may produce excess joint fluid.

The main symptom of shoulder arthritis is pain; this is due to the grinding of the bones against each other because of the lack of cartilage. Pain usually occurs in the front of the shoulder and is worse with motion. People with shoulder arthritis will also experience moderate to severe weakness, stiffness developing over many years, and the inability to sleep on the affected shoulder.

Shoulder arthritis is a clinical condition in which the joint that connects the ball of the arm bone (humeral head) to the shoulder blade socket (glenoid) has damaged or worn out cartilage. Normally the ends of the bone are covered with hyaline articular cartilage, a surface so smooth that the friction at the joint is less than that of an ice skate on ice. In arthritis, this cartilage is progressively lost, exposing the bone beneath. Shoulder arthritis is characterized by pain, stiffness, and loss of function and often by a grinding on shoulder motion.

One of the three forms of shoulder arthritis is osteoarthritis. Osteoarthritis is the gradual wearing down of the joint cartilage that occurs predominantly in elderly people, and sometimes as the result of overuse in athletes. Post-traumatic arthritis happens after a significant trauma is sustained by the joint, ruining the cartilage. This could be the result of a car accident or after repeated trauma. Rheumatoid arthritis is a disease where the body attacks its own cartilage and destroys it. In each of these cases, cartilage is being destroyed.

The exact cause is unknown. Mechanical factors, dietary and long term use of some antidepressants may be of significance. There is a correlation between these factors but not a cause or effect. The distinctive radiological feature of DISH is the continuous linear calcification along the antero-medial aspect of the thoracic spine. The disease is usually found in people in their 60s and above, and is extremely rare in people in their 40s and 30s. The disease can spread to any joint of the body, affecting the neck, shoulders, ribs, hips, pelvis, knees, ankles, and hands. The disease is not fatal, however some associated complications can lead to death. Complications include paralysis, dysphagia (the inability to swallow), and pulmonary infections. Although DISH manifests in a similar manner to ankylosing spondylitis, these two are totally separate diseases. Ankylosing spondylitis is a genetic disease with identifiable marks, and affects organs. DISH has no indication of a genetic link, and does not affect organs other than the lungs, which is only indirect due to the fusion of the rib cage.

Long term treatment of acne with vitamin derived retinoids, such as etretinate and acitretin, have been associated with "extraspinal" hyperostosis.

In the past, there have been speculations about possible complications after transient synovitis. The current consensus however is that there is no proof of an increased risk of complications after transient synovitis.

One such previously suspected complication was coxa magna, which is an overgrowth of the femoral head and broadening of the femoral neck, accompanied by changes in the acetabulum, which may lead to subluxation of the femur. There was also some controversy about whether continuous high intra-articular pressure in transient synovitis could cause avascular necrosis of the femoral head (Legg-Calvé-Perthes disease), but further studies did not confirm any link between the two conditions.

Sacroiliitis is a condition caused by inflammation within the sacroiliac joint. This joint is located where the base of the spine, known as the sacrum, and the pelvis, known as the ilium, intersect. "Itis" is a latin term denoting inflammation.

Since sacroiliitis can describe any type of inflammation found within the sacroiliac joint, there can be a number of issues that cause it. These include:

- Degenerative arthritis, or osteoarthritis of the spine, can cause degeneration within the sacroiliac joints and lead to inflammation and joint pain.

- Any form of spondyloarthropathies, which includes ankylosing spondylitis, psoriatic arthritis, reactive arthritis or arthritis related to inflammatory bowel diseases, including ulcerative colitis or Crohn's disease.

- Pregnancy can cause inflammation as a result of the widening and stretching of the sacroiliac joints to prepare for childbirth. Additionally, the added weight carried during childbearing can put an extra amount of stress on the SI joints, leading to abnormal wear.

- Traumatic injury such as a fall or car crash that affects the lower back, hips, buttocks or legs.

- Though rare, infection within the sacroiliac joints or another part of the body, such as a urinary tract infection, can cause inflammation.

The exact cause is unknown. Some doctors believe it is caused by abnormal metabolism of fat. Others think it may be caused by repetitive inflammation. Some feel that blood within the joint may cause the inflammatory change. Risk factors for PVNS developing are not yet understood. Very little research has been carried out. However, a common theme in patients is a trauma experienced to the joint prior to the onset of symptoms.

Despite much research, the causes remain unclear but include repetitive physical trauma, ischemia (restriction of blood flow), hereditary and endocrine factors, avascular necrosis (loss of blood flow), rapid growth, deficiencies and imbalances in the ratio of calcium to phosphorus, and problems of bone formation. Although the name "osteochondritis" implies inflammation, the lack of inflammatory cells in histological examination suggests a non-inflammatory cause. It is thought that repetitive microtrauma, which leads to microfractures and sometimes an interruption of blood supply to the subchondral bone, may cause subsequent localized loss of blood supply or alteration of growth.

Trauma, rather than avascular necrosis, is thought to cause osteochondritis dissecans in juveniles. In adults, trauma is thought to be the main or perhaps the sole cause, and may be endogenous, exogenous or both. The incidence of repetitive strain injury in young athletes is on the rise and accounts for a significant number of visits to primary care; this reinforces the theory that OCD may be associated with increased participation in sports and subsequent trauma. High-impact sports such as gymnastics, soccer, basketball, lacrosse, football, tennis, squash, baseball and weight lifting may put participants at a higher risk of OCD in stressed joints (knees, ankles and elbows).

Recent case reports suggest that some people may be genetically predisposed to OCD. Families with OCD may have mutations in the aggrecan gene. Studies in horses have implicated specific genetic defects.

Gout is usually present with recurrent attacks of acute inflammatory arthritis (red, tender, hot, swollen joint). It is caused by elevated levels of uric acid in the blood that crystallizes and deposits in joints, tendons, and surrounding tissues. Gout affects 1% of individuals in Western populations at some point in their lives.

Sacroiliitis (say-kroe-il-e-I-tus) is a medical condition caused by any inflammation within one, or both, of the sacroiliac joints. Sacroiliitis is a feature of spondyloarthropathies, such as axial spondyloarthritis (including ankylosing spondylitis), psoriatic arthritis, reactive arthritis or arthritis related to inflammatory bowel diseases, including ulcerative colitis or Crohn's disease. It is also the most common presentation of arthritis from brucellosis.

Several risk factors of CMC OA of the thumb are known. Each of these risk factors does not cause CMC OA by itself, but acts as a predisposing factor influencing the process of OA in some way. Risk factors include: female gender, suffering from obesity, repetitive heavy manual labor, familial predisposition and hormonal changes, such as menopause.

Bone mineral density decreases with increasing age. Osteoporotic bone loss can be prevented through an adequate intake of vitamin C and vitamin D, coupled with exercise and by being a non-smoker. A study by Cheng et al. in 1997, showed that greater bone density indicated less risk for fractures in the calcaneus.

Arthrofibrosis of the knee has been one of the more studied joints as a result of its frequency of occurrence. Beyond origins such as knee injury and trauma, arthrofibrosis of the knee has been associated with degenerative arthritis. Scar tissues can cause structures of the knee to become contracted, restricting normal motion. Depending on the site of scarring, knee cap mobility and/or joint range of motion (i.e. flexion, extension, or both) may be affected. Symptoms experienced as a result of arthrofibrosis of the knee include stiffness, pain, limping, heat, swelling, crepitus, and/or weakness. Clinical diagnosis may also include the use of magnetic resonance imaging (or MRI) to visualize the knee compartments affected.

The consequent pain may lead to the cascade of quadriceps weakness, patellar tendon adaptive shortening and scarring in the tissues around the knee cap—with an end stage of permanent patella infera—where the knee cap is pulled down into an abnormal position where it becomes vulnerable to joint surface damage.

Patients who are recognized as developing arthrofibrosis may improve motion with appropriately directed physical therapy, corticosteroid injections, non-steroidal anti-inflammatory drugs, and cryotherapy. In many instances, however, as fibrosis has set in, surgical intervention is necessary. Specialized arthroscopic lysis of adhesions knee procedures such as anterior interval releases may be indicated and utilized to great success, in the hands of an appropriately trained specialist.

If an individual has injured his or her knee, he or she may note bruising on the front, sides or rear of the knee. Bearing weight on the knee joint may be impossible and the pain unbearable.bruising may be seen as bluish lesion.

Trauma from ligamentous, osseous or meniscal injuries can result in an effusion. These are often hemarthrosis or bloody effusions.

Arthrofibrosis (from Greek: "arthro-" joint, "fibr-" fibrous and "-osis" abnormality) is a complication of injury or trauma where an excessive scar tissue response leads to painful restriction of joint motion, with scar tissue forming within the joint and surrounding soft tissue spaces and persisting despite rehabilitation exercises and stretches. Scarring adhesions has been described in most major joints, including knees, shoulders, hips, ankles, and wrists as well as spinal vertebrae.

Transient synovitis of the hip (also called toxic synovitis; see below for more synonyms) is a self-limiting condition in which there is an inflammation of the inner lining (the synovium) of the capsule of the hip joint. The term irritable hip refers to the syndrome of acute hip pain, joint stiffness, limp or non-weightbearing, indicative of an underlying condition such as transient synovitis or orthopedic infections (like septic arthritis or osteomyelitis). In everyday clinical practice however, irritable hip is commonly used as a synonym for transient synovitis. It should not be confused with sciatica, a condition describing hip and lower back pain much more common to adults than transient synovitis but with similar signs and symptoms.

Transient synovitis usually affects children between three and ten years old (but it has been reported in a 3-month-old infant and in some adults). It is the most common cause of sudden hip pain and limp in young children. Boys are affected two to four times as often as girls. The exact cause is unknown. A recent viral infection (most commonly an upper respiratory tract infection) or a trauma have been postulated as precipitating events, although these are reported only in 30% and 5% of cases, respectively.

Transient synovitis is a diagnosis of exclusion. The diagnosis can be made in the typical setting of pain or limp in a young child who is not generally unwell and has no recent trauma. There is a limited range of motion of the hip joint. Blood tests may show mild inflammation. An ultrasound scan of the hip joint can show a fluid collection (effusion). Treatment is with nonsteroidal anti-inflammatory drugs and limited weight-bearing. The condition usually clears by itself within seven to ten days, but a small group of patients will continue to have symptoms for several weeks. The recurrence rate is 4–17%, most of which is in the first six months.

Although the condition is degenerative, it can occur in patients who are relatively young, particularly active sports people who have at some time suffered trauma to the joint (turf toe). A notable example is NBA star Shaquille O'Neal who returned to basketball after surgery.

Diffuse idiopathic skeletal hyperostosis (DISH) is a non-inflammatory spondyloarthropathy which predominantly affects the spine. It is characterized by ankylosis and enthesopathy (ossification of the ligaments and entheses). It most commonly affects the thoracic and thoraco-lumbar spine, but involvement is variable and can include the entire spine.