Musculoskeletal abnormalities

"Nearly 20% of Down syndrome (DS) patients have musculoskeletal disorders. These are primarily those associated with severe ligamentous laxity including upper cervical instability, patellar and hip dislocations, and severe flatfoot and bunion deformities. They may also present with a polyarticular arthritis with subluxations and swelling. These patients should have a rheumatologic evaluation."

Some of these abnormalities are due to a gene defect on Chromosome 21 that encodes for collagen (type VI). Collagen is an important protein component of ligaments, tendons, cartilage, bone and the support structure of the skin. Type VI collagen abnormalities are associated with muscle hypotonia, ligamentous laxity, bone malformation and joint hypermobility.

Spine - About 15 % of the individuals with Down syndrome have increased mobility of the cervical spine at the level of occiput-C1 and C1-C2, a condition known as atlantoaxial instability (AAI). Most are asymptomatic, but about 10% of those with AAI have symptoms of spinal cord compression (neck pain, torticollis, change in gait, loss of upper body strength, or changes in bowel/bladder functioning). It’s important for nurses to report any of these changes to the primary health care provider as soon as they occur, in order to prevent further complications.

Most symptomatic AAI presents between ages 5 and 15. Nurses can guide the adolescent away from exercise and sports that present high risk for persons with AAI. For example, Special Olympics, Inc. bars athletes with AAI from competing in equestrian sports, diving, alpine skiing, snowboarding, and other sports that increase the risk for spinal cord compression.

Symptomatic scoliosis may become more problematic as the adolescent progresses to adulthood. Surgical correction may be required.

Hips - DS patients are "subject to spontaneous dislocation with otherwise normal appearing hip joints on radiograph. Four stages have been described – initial, subluxation, dislocation, and fixed. In the early phases, the hips can be reduced and will sometimes respond to immobilization. Several surgical recommendations have been made including addressing femoral anteversion and capsular redundancy or both femoral and acetabular osteotomies with success. In older patients, successful periacetabular osteotomies and total hip arthroplasty have both been reported. Slipped capital femoral epiphysis can also occur and may be associated with hypothyroidism."

Knees - DS predisposes to patellofemoral instability. Laxity of the knee ligaments can allow the patella to tract outside the femoral groove. The patella is usually displaced laterally which can cause discomfort and reduced mobility. If identified early and the patient is capable of muscle strength training, patellofemoral instability may be treatable with vastus medialis obliquus exercises. The vastus medialis obliquus is a muscle in the inner thigh which pulls the patella medial.

Feet - Pes planus or flat foot is common in DS. Hammertoe may occur over time as a result of hypotonia and contractures.

Teens with Down syndrome and AAI should not participate in organized sports or other forms of therapeutic recreation.