Knee to knee – what does it mean and why is it important?

Knee to knee is one of the most commonly heard phrases on forums and other discussion places during conversations of whether a sling fits properly.

So what does knee to knee mean?

When a baby is positioned in a sling it is important that a few rules are followed to ensure a correct physiological position is achieved to avoid excessive stresses and strains put on a babies developing muscles and bones and to avoid potential long-term effects on spinal, hip and joint health.

Knee to knee refers to the support the sling or carrier gives to your baby’s thighs. The idea in a sling is that the baby sits on their bottom in a position which looks like a squat. (this position has various names including supported squat, M-Position, frog or froggy leg position and spread squat). It is a position that a baby naturally adopts when being held and when laying down.

Before he reaches 3-4 months, Baby’s knees should be open as wide as his pelvis, with his ankles on the same axis as his knees.

It is important that you think about the knees being higher than bum and not stretching the legs around the wearer.

At about 3-4 months, as Baby discovers new motor skills, he can grab his ankles and naturally open his pelvis, he can now «embrace» the wrapper with his knees.

JPMBB (makers of a hybrid stretchy wrap) have some wonderful images showing the difference between a newborn knee to knee position and that for an older baby. As a guide if you recline on a sofa and hold your

baby against you and see and feel how the legs naturally sit this is the position they should adopt in a sling.

 

 

 

 

So why this position?

Thigh is supported to the knee joint. The forces on the hip joint are minimal because the legs are spread, supported, and the hip is in a more stable position.

At birth a baby’s hips are not fully formed. The hip joint is made where the ball of the femur fits into the socket of the pelvic bone. At birth the

Thigh NOT supported to the knee joint. The resulting forces on the hip joint may contribute to hip dysplasia.

edges of the socket joint are made of cartilage and easily damaged. If the legs are forced or allowed to be in a stretched out position too early the ball of the femur can permanently damage the socket (hip dysplasia) It is also easy for the hips to slip out of the socket completely (hip dislocation). These problems may not be picked up on until walking age and can cause painful arthritis in adulthood. Babies are particularly at risk of hip dysplasia and dislocation in the first few months of life.

The International Hip Dysplasia Institute states “The healthiest position for the hips is for the hips to fall or spread (naturally) apart to the side, with the thighs supported and the hips and knees bent…….. Any device that restrains a baby’s legs in an unhealthy position should be considered a potential risk for abnormal hip development. It is also important to assess the size of the baby and match the device and carrier to the size of the child so that the hips can be in a healthy position during transport”

If the legs are forced into a straightened position it can also cause an unnatural curve of the spine. A newborn baby’s spine does not have the ‘S’ shaped curve of an adults spine. This develops over time as the baby learns to sit, crawl and walk. A newborn baby’s spine is curved in a ‘C’ position and should be maintained and supported that way. Chiropractor’s and osteopaths point to an increased risk of damage to the spine for babies whose spine is not supported in the ‘C’ shape. Whihc can be a cause of back pain and problems in adult life.

So how does this affect the position of your baby in a sling?

Incorrect and correct positioning in different slings

(Above courtesy of Portamor Bebes)

In order to ensure a correct postural position in a sling it is essential that there is enough support for the thighs so the baby is supported in the spread squat position.  The seat of the sling or carrier need to fit from the back of one knee to the back of the other (also called knee pit to knee pit or simply knee to knee).

Another advantage of ensuring this position in a wrap, ring sling or pouch means that the baby is secure in the carrier and is in no danger of falling out. As the material is positioned to provide a deep hammock seat for the baby.

This shows the difference in positioning with a carrier that is too narrow and one that is the correct fit

 

 

 

With Mei Tae’s and Soft Structured Carriers (or buckled carriers) this can cause some problems with fitting as the seat width is much more fixed and can be grown out of, at times quite quickly. Some carriers come with adjustable seats and there are ways of adapting the width of the seat.   (Check out this video of how to extend the seat of a structured carrier using a doll sling or scarf)

 

 

 

 

 

 

Links
International Hip dysplasia Institute (Images of hip joints from this page)

Infant Carriers and Spinal Stress Rochelle L Casses DC

Infant Spinal Developemnt and Correct Baby Carrier SupportAnniker Kral (Senior Manager Researcher, Babes in Arms)

JPMBB Article ‘How do I know my baby’s legs aren’t Forced into a Squat (Images of the newborn and four month positioning from this page)

How to Extend the Seat of a SSC