Background: Post-traumatic knee osteoarthritis (PTOA) is a leading cause of medical
separation from military service. Anterior cruciate ligament (ACL) injury and surgical
reconstruction (ACLR) incurs a high PTOA risk. Aberrant gait biomechanics contribute to
PTOA development and are attributable to quadriceps muscle dysfunction. Additionally, up
to 30% of patients experience secondary ACL injury. Aberrant landing biomechanics
contribute to secondary ACL injury risk and are influenced by quadriceps dysfunction.
Vibration acutely improves quadriceps function and gait biomechanics in individuals with
ACLR, but its effects on joint health, PTOA risk, and landing biomechanics are unknown.
Hypothesis/Objective: This study will evaluate the effects of vibration embedded in ACLR
rehabilitation on quadriceps function, gait biomechanics, landing biomechanics, patient
self-report outcomes, return-to-physical-activity (RTPA) criteria, and MRI indicators of
knee joint health. The central hypothesis is that vibration will enhance gait and landing
biomechanics consistent with reduced PTOA and secondary ACL injury risks, respectively,
and that whole body vibration (WBV) delivered by a commercial device and local muscle
vibration (LMV) delivered by a prototype device will produce equivalent improvements in
the study outcomes. The rationale for the hypothesis is that vibration will more
effectively improve quadriceps function compared to standard rehabilitation, thus
restoring normal biomechanics and mitigating declines in joint health.
Specific Aim 1: To compare the effects of Standard rehabilitation vs. Vibration
rehabilitation (WBV and LMV) on quadriceps function. The investigators hypothesize that
Vibration will produce superior outcomes (e.g. strength) compared to Standard
rehabilitation, but that WBV and LMV will produce similar outcomes.
Specific Aim 2: To compare the effects of Standard rehabilitation vs. Vibration
rehabilitation on gait biomechanics linked to PTOA development. The investigators
hypothesize that Vibration will produce superior outcomes compared to Standard
rehabilitation, but that WBV and LMV will produce similar outcomes.
Specific Aim 3: To compare the effects of Standard rehabilitation vs. Vibration
rehabilitation on patient self-report outcomes. The investigators hypothesize that
Vibration will produce superior outcomes compared to Standard rehabilitation, but that
WBV and LMV will produce similar outcomes.
Specific Aim 4: To compare the effects of Standard rehabilitation vs. Vibration
rehabilitation on MRI indicators of knee joint health. The investigators hypothesize that
cartilage composition (e.g. collagen, water, and proteoglycan content) will be poorer and
PTOA incidence (MOAKS score) will be higher in the Standard cohort compared to both
Vibration cohorts, but that WBV and LMV will produce similar outcomes.
Specific Aim 5: To compare the effects of Standard rehabilitation vs. Vibration
rehabilitation on landing biomechanics linked to secondary ACL injury risk. The
investigators hypothesize that Vibration will produce superior outcomes compared to
Standard rehabilitation, but that WBV and LMV will produce similar outcomes.
Specific Aim 6: To compare the effects of Standard rehabilitation vs. Vibration
rehabilitation on the probability of meeting evidence-based RTPA criteria (e.g.
single-leg hop symmetry ≥90%). The investigators hypothesize that Vibration will display
result in greater probabilities of meeting RTPA criteria compared to Standard
rehabilitation at 6 months and 1 year post-ACLR, but that WBV and LMV will produce
similar outcomes.
Specific Aim 7: To evaluate changes in quadriceps muscle quality over the first year
following ACLR reconstruction surgery. The investigators hypothesize that quadriceps
muscle quality will decline at 1, 6 and 12 months post-ACLR compared to preoperative
measurements and that these changes will be more pronounced in the ACLR limb compared to
the uninjured limb at 1, 6 and 12 months post-ACLR.
Specific Aim 8: To evaluate associations between changes in quadriceps muscle quality
over the first year following ACLR. The investigators hypothesize that declines in muscle
quality between preoperative and 1- and 6- months post-ACLR timepoints will be associated
with lesser knee extensor strength, aberrant gait biomechanics, worse patient self-report
and functional outcomes, and deleterious alterations in knee cartilage composition.
Specific Aim 9: To compare the effects of Standard rehabilitation vs. Vibration
rehabilitation on quadriceps muscle quality. The investigators hypothesize that Vibration
will produce superior outcomes compared to Standard rehabilitation, but that WBV and LMV
will produce similar outcomes.
Study Design: The approach will be to recruit ACLR patients at the onset of
rehabilitation and conduct a Phase II single-blind randomized controlled trial to compare
the effects of standard ACLR rehabilitation (control) vs. standard rehabilitation that
incorporates WBV or LMV on the study outcomes over the first year post-ACLR.
Impact: This study will evaluate the effects of a novel rehabilitation approach on
factors related to the risks of PTOA and secondary ACL injury following ACLR. ACL injury
risk is 10x greater in military personnel vs. civilians, and PTOA is a leading cause of
medical separation from military service, degrades quality of life, increases the risks
of several comorbidities (e.g. obesity), and is a primary contributor to years of life
lost due to disability. Improving rehabilitation of knee injuries is paramount for
maintaining the combat readiness of the armed forces and preserving the health and
well-being of Service members and Veterans, as well as millions of Americans at risk of
PTOA. Vibration represents a promising approach to this important challenge. Furthermore,
in addition to being cost-effective, the portable nature of the prototype LMV device
could have substantial implications for military personnel and US citizens, particularly
those with limited access to rehabilitation facilities.
