Failure of the tricuspid valve to close sufficiently upon contraction of the right ventricle, causing blood to regurgitate (flow backward) into the right atrium.

Weakness of the hip girdle and upper thigh muscles, for instance in myopathies, leads to an instability of the pelvis on standing and walking. If the muscles extending the hip joint are affected, the posture in that joint becomes flexed and lumbar lordosis increases. The patients usually have difficulties standing up from a sitting position. Due to weakness in the gluteus medius muscle, the hip on the side of the swinging leg drops with each step (referred to as Trendelenburg sign). The gait appears waddling. The patients frequently attempt to counteract the dropping of the hip on the swinging side by bending the trunk towards the side which is in the stance phase (in the German language literature this is referred to as Duchenne sign). Similar gait patterns can be caused by orthopedic conditions when the origin and the insertion site of the gluteus medius muscle are closer to each other than normal, for instance due to a posttraumatic elevation of the trochanter or pseudarthrosis of the femoral neck.

A type of Developmental delay characterized by a delay in acquiring motor skills.

Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.

Osteopenia is a term to define bone density that is not normal but also not as low as osteoporosis. By definition from the World Health Organization osteopenia is defined by bone densitometry as a T score -1 to -2.5.

Reduced strength of muscles.

Reduced strength of one or more muscles innervated by the facial nerve (the seventh cranial nerve).

The distal interphalangeal joint and/or the proximal interphalangeal joint of the fingers or toes cannot be extended to 180 degrees by either active or passive extension.

An abnormally high degree of muscle fiber size variation. This phenotypic feature can be observed upon muscle biopsy.

The capability that a joint (or a group of joints) has to move, passively and/or actively, beyond normal limits along physiological axes.

An abnormal predominance of type I muscle fibers (in general, this feature can only be observed on muscle biopsy).

Muscle fibers degeneration resulting in fatty replacement of skeletal muscle fibers

An abnormal reduction in the amount of air a person can expel following maximal inspiration.

A loss of the ability to move the vocal folds.

The presence of excess amniotic fluid in the uterus during pregnancy.

An abnormal reduction in quantity or strength of fetal movements.