Neural control of knee laxity in functional tasks after an ACL reconstruction

Despite improvements after an anterior cruciate ligament (ACL) reconstruction
(ACLR), return to sport rate is only 1/3 one year after surgery. Some patients
might manage to return to sport (copers) because they might develop strategies
to compensate for the increase in anterior tibia translation (knee laxity or
ATT) in an active situation. They might compensate by effective muscle
activation patterns, whereas other patients who do not manage to return to
sport (non-copers) might rely more on the strain of the ACL. This suggestion
can be supported by the finding of Kvist (2005) that there is no correlation
between passive ATT and active ATT, which suggests that the ATT during activity
is controlled by other factors than the strain of the ACL, i.e. muscle
activation patterns or the anatomy of the knee. It might be that the ATT is
related to the slope of the tibia plateau. The current study will add to the
literature knowledge about the control of the ATT in an active situation in
ACLR patients. It is hypothesized that copers can compensate for an increase in
active ATT after an ACLR by developing effective muscle activation patterns in
agreement with their anatomy, whereas other patients cannot compensate for the
results of the injury.

The aim is to uncover possible muscle activation patterns to control the active
ATT after an ACLR.

Three studies will be conducted. The designs of the studies will be
observational studies. Measurements for all studies will take place in the same
session. The session takes about one hour where participants are measured in a
gait lab. Participants will undergo a passive test of anterior- and posterior
tibia translation* (KT-1000 arthrometer) and perform an active test (single hop
for distance). Next, to the experimental tests, a short questionnaire with
general questions and questions about sports resumption will be filled in by
the patients. Patients will be tested one to two years after ACLR. The slope of
the tibia plateau will be measured using MRI*s or, if MRI*s are not available
for a participant, X-Ray*s, already taken before surgery (care as usual).

To validate the method to determine the anterior- posterior tibia translation,
one patient with a total knee arthroplasty, without possibility to anteriorly
and posteriorly translate the tibia relative to the femur, will be tested.

Forty participants will be tested in one session which will take about one
hour. Minimal risk or discomforts, as physical injury or harm, to the subjects
as a result of each procedure is involved in the studies.