The most common injury of the knee joint in athletes, as well as
football players, is the rupture of the anterior cruciate ligament (ACL).
Biomechanics of one or more years after the injury of ACL, treated without
reconstruction in athletes is poorly studied. Existing researches which cope
with that problem have a consensus, that one of the consequence of ACL rupture
is an increased anterior translation of the tibial platao. The aim of this
pilot study was to determine differences in some biomechanical parameters
between a stable and unstable knee joint during normal, self-selected walking speed
in order to gain an insight into the possible compensatory strategies. A
high-speed camera (120 Hz) and reflective markers placed on lower limbs were
used to record 10 steps in the stance phase of one subject (female, age: 39
years, high: 158.5 cm, body mass: 45.0 kg) with a total rupture of ACL
(mechanically unstable, but functionally stable knee joint) 3 years after the
injury. A kinematic analysis was done to calculate the angle of the left and
right knee joint. At the same time ground reaction forces were measured on a
force plate and the average net muscular torque for both knees was calculated
using the inverse dynamics. The independent samples T-test or Mann-Whitney U
test showed a significantly (p=0.000) greater extension of the unstable knee, but
the net muscular torque was not significantly different. It is known that total
rupture of ACL leads to the development of premature knee arthrosis. It could
be expected that the net muscular torque would be the primary reason for
damaging the cartilage, but the results of this pilot study showed that the
loads on an unstable knee joint were not increased. Increased torque is
probably not the primary reason for developing premature knee arthrosis, but it
could be the changes in instantaneous axis of rotation because of increased
knee extension carried much more influence. The use of a physiotherapeutic
technique of manual kinematic re-education might enable a decrease of knee
extension and so might lead to a more equal loading on the knee joint cartilage
in persons treated conservatively. A total rupture of ACL, even 3 years after
injury affects biomechanics of the unstable knee joint during gait. Due to a
great potential of re-injury of the knee joint that leads to meniscal lesion,
most athletes decide to reconstruct the ACL. On the other hand, for those who
decide to be treated conservatively the impact of the manual kinematic
reeducation on knee biomechanics should be further explored, as well as the
possible reasons for the increased knee extension angle such as differences in
muscle activation between mechanically stable and unstable knee joint.
