Definition of Arthrogryposis

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Arthrogryposis: Joint contractures that develop before birth (prenatally) and are evident at birth (congenitally). A newborn with arthrogryposis lacks the normal range of motion in one or more joints.

In normal embryonic development, the joints begin to develop by about 5 to 6 weeks of gestation. There are joint spaces by 7 weeks, and the limbs can be seen moving by 8 weeks. This motion of joints is clearly essential to the proper development of the joints and structures around the joints. Limitation of joint motion before birth leads to joint contractures. Prenatal limitation of joint mobility can result from:

• Neurologic deficits: Including anencephaly, defects of the spine such as spina bifida (meningomyelocele), and nerve deficiencies.

• Muscle deficits: Including failure of muscle development (agenesis of muscle), fetal diseases of muscle (fetal myopathies), myotonic dystrophy, and myasthenia gravis.

• Connective tissue and skeletal defects: Including fusion of bones (synostosis), failure of a joint to develop, prenatal fixation of a joint, excess laxity and of dislocation of joints, and fixation of soft tissue around the joint.

• Fetal crowding or constraint: Not enough room for the fetus to move around freely in multiple births. Fetal constraint occurs from lack of amniotic fluid (oligohydramnios) due to underproduction of fluid by the fetal kidneys, failure to swallow and recirculate the fluid, or chronic leakage of fluid.

Arthrogryposis means crooking of the joint. It comes from the Greek "arthro-" (joint) + "gryposis " (crooking).