Document Title: DeVita-AJSM-Nov98

Article Title: Functional knee brace effects during walking in patients with anterior-cruciate-ligament reconstruction

Authors: Paul DeVita, Tally Lassiter Jr, Tibor Hortobagyi, Michael Torry.

Publication: The American Journal of Sports Medicine

ISSN: 03635465

Date: November-December 1998.

(Figures included. Reference-denoting numbers appear in the same point size as document text.)

Volume: 26

Issue: 6

Pages: 778-784

Key Words: Knee, bracing, ACL reconstruction, neuromuscular, kinetics, proprioception.

 

The authors found that the wearing of a brace encourages more use of hip-centred musculature and less use of quadriceps (which are knee-centred); they concluded that bracing could be helpful in developing gait adaptations. The authors note that activation of the quadriceps tends to strain the ACL, and so by encouraging slightly reduced quadriceps use, the brace would indirectly reduce ACL strain. (Note that many muscle groups, including the quadriceps and hamstrings, actually operate more than one joint anyway. The hamstrings and quadriceps both mainly operate the knee, but they happen to operate the hip too. Only via the automatic co-contraction of the appropriate muscles can the human body ensure that the desired joint movements are obtained.) Apparently, wearing a brace causes no effect on the hamstrings; this situation is desirable because hamstring activation is very beneficial in protecting the ACL. Keep in mind that functional braces are mostly used intermittently (e.g. only for sports), and so would not engender lasting effects on the leg muscles. (The sometimes-heard "braces cause weak muscles" would only be true if the person would both discontinue exercising and wear bracing 24/7, or at least continuously while awake). Used judiciously and with understanding of the underlying biomechanical principles involved, knee-bracing does not cause harm and does provide valuable protection against side impacts and hyperextension.

 

ABSTRACT

 

The purpose of this study was to compare lower extremity joint kinematics and kinetics during walking with and without a functional knee brace in patients with recent anterior-cruciate-ligament reconstructions. Seven volunteers walked at 1.26 m/s with and without one of two functional knee braces 3 weeks after surgery. Eleven uninjured subjects were also tested as a control group. Video and ground-reaction data were collected and combined with inverse dynamics to estimate the joint positions, moments, and powers during the stance phase. Patients with ligament reconstructions were more erect with the brace, using 19% less knee flexion compared with walking without the brace. Areas under the internal extensor moment curve (angular impulse) and power curve (work) at the hip increased 40% and 44%, respectively, while walking with the brace. Extensor angular impulse decreased 41% at the knee while using the brace, and plantar flexor angular impulse and work increased 21% and 30%, respectively, at the ankle. While walking with the brace, the patients still had different kinematics, moments, and powers than the control subjects. The reduced extensor moment at the knee in the braced condition indicated that the load on the recently reconstructed ligament was reduced and that the brace protected the ligament during the stance phase of walking. We concluded that functional knee braces may be one means of developing neuromuscular adaptations during gait after anterior cruciate ligament reconstruction surgery.

 

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