What is a one-sentence summary of the following article?
Babies with low muscle tone are usually described as floppy or feeling like a "rag doll" when held. This condition is known as hypotonia. Infants usually have flexed elbows and knees, whereas those with low muscle tone have loosely extended joints.  While infants with normal tone can be lifted and held from under the armpits, babies with hypotonia typically slip from their parents' hands because their arms rise without resistance.  Hypotonia results in weaker stomach muscles. Therefore, the stomach may extend outward more than usual.  Poor muscle control of the head (head rolling to the side or forward and backward) is also a symptom. Children affected by Down Syndrome often grow slower than other children, and are therefore shorter in stature. Newborns with Down Syndrome are usually small, and a person with Down Syndrome will most likely remain short through adulthood.  A study conducted in Sweden shows that the mean birth length is 48 centimeter (18.9 in) for both males and females with Down Syndrome. In comparison, the average length for those without the disability is 51.5 cm. Also look for excess fat or skin surrounding the neck. In addition, neck instability tends to be a common issue. While neck dislocation is uncommon, it is more likely to occur in people with Down Syndrome than those without the disability. Caretakers should be aware of a lump or pain behind the ear, a stiff neck that doesn't heal quickly, or changes in the way a person walks (appearing unsteady on their feet). This includes legs, arms, fingers, and toes. Those with Down Syndrome often have shorter arms and legs, a shorter torso, and higher knees than those without it.  People with Down Syndrome often have webbed toes, which is distinguished by the fusing together of the second and third toe.  There may also be a wide space between the big toe and second toe, and a deep crease on the sole of the foot where this space is. The fifth finger (pinky) can sometimes only have 1 flexion furrow, or place where the finger bends.  Hyperflexibility is also a symptom. This is identifiable by joints that seem to easily extend beyond the normal range of motion. A child with Down Syndrome may easily "do the splits," and may be at risk of falling over as a result. Having one singular crease across the palm of the hand, and a pinky finger that curves towards the thumb are additional characteristics.

Summary:
Look for low muscle tone. Look for shortened height. Look for a short and wide neck. Look for short and stocky appendages.