Study Tests the Role of the Prosthetic Knee for Infants With Limb Loss

PARK CITY, Utah — Infants with limb loss at or
above-the-knee face numerous challenges, especially during the transition from
crawling to walking. According to Colleen Coulter-O’Berry, PhD, PT, DPT,
PCS, Children’s Health Care of Atlanta, the prosthesis must accomplish
competing goals — remain mobile for crawling and stable for standing and
walking. Her study, presented at the
2011 Association of Children’s Prosthetics-Orthotics Clinic
Annual Meeting
, tested the hypothesis that crawling infants and toddlers
with transfemoral amputation or knee disarticulation will flex their prosthetic
knees, crawl faster, and demonstrate less compensatory movements at the hips
and shoulders when the prosthesis is in the unlocked knee condition.

“We started looking at how these infants and
toddlers use knees,” Coulter-O’Berry said here. “We discovered
that as the infants were playing with their toys, perhaps the benefits of a
knee for a young child in a pre-walker knee were in the pre-walking activities
such as the transition from kneeling to upright. That is where they use their
prosthetic knees the most.”

Coulter-O’Berry wanted to know if the prosthetic
knee makes a difference in the infants’ function. Two conditions were
tested: the prosthetic knee in the unlocked, fully articulating position and
the knee locked into extension. Prosthetic knee flexion, hip
abduction/adduction, contralateral limb flexion, crawling pattern and crawling
cadence were measured in five children with limb loss at the transfemoral or
knee disarticulation level. Testing occurred within 3 weeks of the child’s
first fitting.

The results of this study were consistent in all
subjects. Crawling speed was decreased in all subjects in the locked position
of the prosthetic knee. The results also indicated that the infants performed
more crawling steps per minute when the knee was in the unlocked position than
the locked position.

“The toddlers with the unlocked knee were faster
and in the unlocked position they were able to ‘crawl through’
(contralateral knee advancing in front of the ipsilateral knee) and have a
reciprocating crawling pattern,” Coulter-O’Berry explained. “In
the locked position, we were seeing a ‘crawl to’ crawling

Coulter-O’Berry’s study also compared the
toddler’s emotions while wearing a prosthesis in the locked and unlocked

“Looking at emotions opened up a whole can of
worms,” she said. “We looked at videos and scored the facial emotions
of the toddlers. They all could crawl in both the locked and unlocked
positions, however, in the locked position; we found that they were not as

The data indicated, according to Coulter-O’Berry that the
traditional protocol of supplying toddlers and infants with transfemoral
amputation prostheses with locked knees may inhibit crawling, which could
potentially have long-term implications on motor development. — by
Anthony Calabro


The study confirms that an unlocked knee is helpful for
crawling. The next developmental stage is pulling to stand. The toddler
typically pulls up using furniture and then goes down to the floor to crawl
again. As the child stands at a low table or other item, he begins to weight
shift and then to step alongside the piece of furniture. If the knee is not
locked, the leg buckles and the child falls. At this stage the child is up and
down repeatedly throughout waking hours.

The dilemma is whether the knee should meet requirements
for crawling (unlocked) or standing and taking steps (locked). Since standing
and early walking are an advanced developmental stage over crawling, the knee
should probably support standing when the child reaches this stage of
development. The locked knee makes crawling awkward, but certainly possible.
The author suggests that the locked knee inhibits crawling, which may pose a
long-term detriment to motor development. Clinicians have not reported this,
but the question of effect on development suggests that a study should be done
to support or refute this supposition.

— Julie Shaperman, MSPH, OTR/L, FAOTA

Vice president, California Foundation for Occupational Therapy

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