Joint laxity and hypermobility can also be features of hip dysplasia. The prevalence of hip dysplasia is 1 in 100 infants which are treated for hip dysplasia and 1 in 500 infants are born with completely dislocated hips. Hip dysplasia can also develop after birth which is why the preferred terminology is developmental dysplasia of the hip or DDH.

In some patients with hip dysplasia, a connective tissue disorder such as Ehlers-Danlos Syndrome (EDS) can be a cause for their joint laxity. EDS is a group of disorders that affect connective tissues supporting the skin, bones, blood vessels, and many other organs and tissues. Defects in connective tissues cause the signs and symptoms of these conditions, which range from mildly loose joints to life-threatening complications. The prevalence of EDS is suspected to be 1 in 5000 for the most common type (hypermobile) and is even less common the rarer of the 13 subtypes.

A majority of hip dysplasia cases are not related to EDS. There is also “acquired” hypermobility through activities and sports, such as a baseball pitcher having a hypermobile shoulder, a hockey goalie with hypermobile hips, and dancers and gymnasts having more joint hypermobility than the average individual.  The terms “hypermobility” and “flexibility” are often used interchangeably, but actually mean different things. Hypermobility is laxity of the joints and flexibility is length of the muscle.  Flexibility varies by individual but can be trained through activity, such as seen in dancers.  Just because a person is flexible does not mean that they are hypermobile.  Similarly, people with hypermobility may develop decreased flexibility and muscle imbalances over time.

Having acquired hypermobility does not necessarily mean that an individual has EDS. However, because individuals with EDS have joint hypermobility and defects in connective tissue, hip dysplasia is more common in those with the disorder.  Genetic testing for EDS is not necessary for hip dysplasia patients unless other health issues are present.  However, if you suspect that you have EDS, this should be discussed with your primary care provider and a referral to a geneticist may be helpful.

Resources

https://ghr.nlm.nih.gov/condition/ehlers-danlos-syndrome

https://adc.bmj.com/content/80/2/188

Author: Ashley Spalla