Arthrogryposis multiplex congenita (AMC) is a group of conditions that affect the joints and is present at birth. People with AMC have a reduced range of motion in certain joints.
AMC first occurs in newborns due to atypical fetal development in the uterus.
People with AMC do not have a full range of motion in certain joints and may not be able to fully straighten or bend the joint. AMC may affect surrounding muscles and alter how people move or bear weight.
This article looks at the symptoms, causes, diagnosis, and treatments of AMC, including nonsurgical and surgical options.
AMC is the term for a range of conditions involving stiffness of the joints that occurs before birth. People may also refer to AMC as arthrogryposis.
People with AMC have joint contractures, which means they cannot fully straighten or bend a joint. This can affect how the joint moves and functions and may also lead to muscle atrophy, or wasting, around the joint.
Symptoms of AMC usually first appear in newborns. Symptoms may vary depending on the subtype of AMC, which include:
- distal arthrogryposis
- pterygium syndrome
Although there is currently no cure for AMC, treatments can help improve the range of motion and joint function.
According to the National Organization for Rare Disorders (NORD), AMC affects males and females equally. There are reports of it occurring in people with Asian, African, and European ancestry. The condition may affect around 1 in 3,000 individuals.
AMC may occur due to a lack of movement of the fetus during the development stages in the uterus. Joints in a fetus usually begin to develop within the first 5–6 weeks of pregnancy.
Movement is essential to typical joint development, and restricted movement can lead to excess connective tissue developing around the joints. This can limit the natural range of motion of the joints.
Reduced fetal movement may be due to factors such as:
- environmental factors, such as maternal illness, limited space in the uterus, or low levels of amniotic fluid
- single-gene or chromosomal disorders
- disorders affecting the central and peripheral nervous system
- muscle disorders, which people may inherit
- conditions affecting typical connective tissue development, such as metatropic dwarfism or Larsen syndrome
Symptoms of AMC are usually apparent at birth or within the first 4 weeks of life. Symptoms of AMC can vary for each person but may include:
- the involvement of both the arms and legs
- a limited range of movement around small and large joints in the body
- joint contractures that may affect the hands, wrists, elbows, shoulders, hips, knees, and ankles
- muscle weakness
- in some cases, curvature of the spine
- underdeveloped muscles in the limbs, which may feel soft and doughy
- webbing from soft tissue that may develop around affected joints
It is also more common for people with AMC to have:
- cleft palate
- atypically fragile and slender long bones in the arms and legs
- testes that do not descend into the scrotum in males
- abnormalities of the central nervous system
A healthcare professional may detect abnormalities in fetal development during an ultrasound, although there is no diagnostic test for AMC during pregnancy.
In a newborn, a doctor may diagnose AMC if they identify two or more joint contractures affecting separate areas of the body. A doctor may then conduct genetic testing to find out the underlying cause of AMC.
There is currently no cure for AMC, but treatments may help improve the movement and function of the affected joints. Depending on each case, treatments may involve nonsurgical or surgical options.
Nonsurgical treatments that may be beneficial for AMC include:
- physical therapy to improve range of motion and prevent muscle atrophy
- gentle joint manipulation
- stretching exercises
- removable splints for knees and feet to allow for regular movement and exercise
- serial casting, which gradually increases joint mobility
- aquatic therapy, which involves joint strengthening and range of motion exercises in water
- assistive devices for support
- education for parents and carers to ensure the correct positioning and techniques
People may need to work with a team of healthcare professionals, which may include:
- rehabilitation therapists
- medical geneticists
- genetic counselors
It is best to begin nonsurgical treatments for AMC as soon as possible in the early stages of infancy.
If nonsurgical treatments are ineffective at improving joint function and movement, people may require surgery, particularly for AMC that affects certain joints, such as the:
Surgery may help improve positioning and range of motion. In rare cases, people may have tendon transfer surgery. This technique transfers a functioning tendon to an area that is not functioning properly, which may improve muscle function.
Corrective surgeries may help improve joint contractures in the lower body, such as in the hips and knees. This procedure may help improve range of motion, walking, and the ability to bear weight.
If AMC causes curvature of the spine, people may require surgery to correct the positioning of the spine.
The type of surgery may depend on the child’s age, the severity of symptoms, and which joints AMC affects. Following surgery with physical therapy and splinting or bracing may help maintain the correct positioning.
Although there is no cure for AMC currently, nonsurgical and surgical treatment options may help improve range of motion and joint function.
NORD recommends a combination of treatments for the best results in the long term.
AMC is not a progressive disorder, which means symptoms will not worsen over time. According to the American Association of Neuromuscular & Electrodiagnostic Medicine, treatment is important to help prevent further joint issues.
AMC is the term for a range of conditions present from birth that affect multiple joints in the body. People with AMC have joint contractures, meaning they cannot properly straighten or bend certain joints.
AMC may affect joints in the lower and upper body, including the wrists, elbows, hips, knees, and ankles.
Newborns may display symptoms of AMC between birth and 4 weeks of age. Symptoms include joint stiffness, limited range of motion, and muscle weakness.
Nonsurgical treatments focus on improving range of motion and preventing muscle atrophy. These treatments may include physical therapy, splints, and assistive devices.
In some cases, people may require corrective surgery to improve positioning and help increase range of motion and the ability to walk and bear weight.