Globally, bacterial infections are the cause of 10% of maternal deaths—this is more common in low income countries but is also a direct cause of maternal deaths in high-income countries.In the United States, puerperal infections are believed to occur in between 1% and 8% of all births. About three die from puerperal sepsis for every 100,000 births. The single most important risk factor is Caesarean section. The number of maternal deaths in the United States is about 13 in 100,000. They make up about 11% of pregnancy-related deaths in the United States.In the United Kingdom from 1985–2005, the number of direct deaths associated with genital tract sepsis per 100,000 pregnancies was 0.40–0.85. In 2003–2005, genital tract sepsis accounted for 14% of direct causes of maternal death.Puerperal infections in the 18th and 19th centuries affected, on average, 6 to 9 women in every 1,000 births, killing two to three of them with peritonitis or sepsis. It was the single most common cause of maternal mortality, accounting for about half of all deaths related to childbirth, and was second only to tuberculosis in killing women of childbearing age. A rough estimate is that about 250,000–500,000 died from puerperal fever in the 18th and 19th centuries in England and Wales alone.
Another classification is according to the degrees of freedom allowed, and distinguished between joints with one, two or three degrees of freedom. A further classification is according to the number and shapes of the articular surfaces: flat, concave and convex surfaces. Types of articular surfaces include trochlear surfaces. Biomechanical classification
Joints can also be classified based on their anatomy or on their biomechanical properties. According to the anatomic classification, joints are subdivided into simple and compound, depending on the number of bones involved, and into complex and combination joints:
Simple joint: two articulation surfaces (e.g. shoulder joint, hip joint)
Compound joint: three or more articulation surfaces (e.g. radiocarpal joint)
Complex joint: two or more articulation surfaces and an articular disc or meniscus (e.g. knee joint)

Anatomical
The joints may be classified anatomically into the following groups:

Joints of hand
Elbow joints
Wrist joints
Axillary joints
Sternoclavicular joints
Vertebral articulations
Temporomandibular joints
Sacroiliac joints
Hip joints
Knee joints
Articulations of footUnmyelinated nerve fibers are abundant in joint capsules and ligaments as well as in the outer part of intraarticular menisci. These nerve fibers are responsible for pain perception when a joint is strained. Clinical significance
Damaging the cartilage of joints (articular cartilage) or the bones and muscles that stabilize the joints can lead to joint dislocations and osteoarthritis. Swimming is a great way to exercise the joints with minimal damage.A joint disorder is termed arthropathy, and when involving inflammation of one or more joints the disorder is called arthritis. Most joint disorders involve arthritis, but joint damage by external physical trauma is typically not termed arthritis.