Anterior cruciate ligament (ACL) injury is a prevailing problem among sports
participants, especially in non-contact sports. Studies have reported that 70-84% of ACL
injuries are non-contact in nature, and movements like changing in direction while
running, cutting and pivoting on a planted foot have resulted in a majority of ACL
injuries. The influence of such injury can often be lifelong as it increases the
patient's risk of developing degenerative musculoskeletal problems like osteoarthritis,
and eventually affects the patient's quality of life. Even after ACL reconstruction
(ACLR) surgeries, study has reported a 30-50% prevalence of developing patellofemoral
joint (PFJ) pain in 1-2 years post-operation. The prevalence of patients developing PFJ
osteoarthritis ranges from 14.8-26.5% for post-operation 2-5 years, and the percentage is
even higher after more than 6 years post-operation.
Symptoms of PFJ osteoarthritis include swelling, notably reduced quadriceps strength, and
pain on PFJ compression. Though the mechanism of how ACLR contributes to the development
of PFJ osteoarthritis is not completely clear yet, inflammation and damage to PFJ
articular cartilage and alteration of vastus medialis function, which is common after
ACLR, might play a role in the development of PFJ osteoarthritis. A more than 30%
decrease in quadriceps muscles strength had been reported by previous study. Decrease in
size of rectus femoris, vastus medialis and vastus lateralis had also been observed.
Though there was no significant difference in the vastus medialis/vastus lateralis, the
decrease in strength and size of the quadricep muscles could possibly affect the
stability of PFJ, increasing the chance of developing PFJ osteoarthritis.
Whole body vibration (WBV) therapy has been gaining attention as an effective method of
training in recent years. More and more rehabilitation facilities have equipped the WBV
machine and make this therapy more easily accessible. It has been proved to have a
positive effect on improving muscle strength, muscle activities, muscle power and loading
during drop jump. It has also shown effectiveness in decreasing osteoarthritic knee pain
and enhancing knee function in chronic elderly knee osteoarthritis. Though the exact
mechanism of the therapy is not yet very clear, it is believed that it is related to the
"tonic vibration reflex". Skeletal muscles undergo small changes in muscle length during
the vibration generated by the machine. It elicits the "tonic vibration reflex",
activates muscle spindles and mediated neural signals. Another possible mechanism is that
the vibration provides cortical stimulation and increases the corticomotor excitability.
Both of them train the neuromuscular system to response faster, achieving the
above-mentioned benefits.
There are different types of WBV machines, providing vertical, horizontal or pivoting
vibration, and the amplitude and frequency of the vibration can be adjusted on the
machine. Many studies have been conducted using different duration, amplitude and
frequency of vibration. A "standard protocol" for WBV therapy is yet to be developed.
Though duration of WBV may differ according to the effect of interest, several studies
have had positive results with a 8 week WBV therapy in increasing muscle strength,
proprioception, and post-ACLR knee functions. Further investigation on the underlying
mechanism and possible application are to be continued to explore more possibilities with
the WBV therapy.
Conservative and effective approaches for relieving pain are needed for knee
osteoarthritis patients and, among these, pulsed electromagnetic fields (PEMF) are
emerging with promising results. In vitro studies have demonstrated that PEMF therapy is
effective in reducing chondrocyte apoptosis and MMP-13 expression of knee cartilage in
ovariectomized rats and in favourably affecting cartilage homeostasis. PEMF was evaluated
for function, a significant improvement was observed 8 weeks after initiation of
treatment, and no significant association was found between the use of PEMF and the
occurrence of adverse events.
