Greater Quadriceps Strength May
Benefit Those With Knee Osteoarthritis
Studies on the influence of quadriceps strength on knee osteoarthritis
(OA), one of the leading causes of disability among the elderly,
have shown conflicting results. In some studies, decreased quadriceps
strength is associated with greater knee pain and impaired function,
while other studies show mixed results on the effect of quadriceps
strength on the structural progression of knee OA.
Most studies to date have used X-rays to indirectly measure
cartilage loss in knee OA and have focused on the tibiofemoral
joint (the main joint in the knee where the thigh and shin bones
meet). A new study has examined the effect of quadriceps strength
on cartilage loss (measured using magnetic resonance imaging [MRI])
at both the tibiofemoral joint and the patellofemoral joint (where
the thigh bone and knee cap meet) as well as on knee OA symptoms.
Led by Shreyasee Amin, M.D., M.P.H., of the Mayo Clinic, the
study involved 265 men and women participating in a 30-month study
of symptomatic knee OA. At the beginning of the study, participants
underwent MRI of their more painful knee and measurement of quadriceps
strength for the same knee. They were also asked to rate the severity
of their knee pain and their physical function was assessed. The
knee MRI and assessments of their knee OA symptoms were repeated
at 15 and 30 months. A measurement of knee alignment was also
performed.
The results showed that greater quadriceps strength had no influence
on cartilage loss at the tibiofemoral joint even in those with
knees that were out of alignment. However, stronger quadriceps
were shown to protect against cartilage loss in the lateral compartment
(outer part) of the patellofemoral joint, a site of frequent cartilage
loss, pain and disability in patients with knee OA. The study
also showed that those with the greatest quadriceps strength had
less knee pain and better physical function than those with the
least strength.
Previous studies had also shown no overall protective effect
of greater quadriceps strength on cartilage loss at the tibiofemoral
joint. The protective effect against cartilage loss at the lateral
compartment of the patellofemoral joint is a new finding that
needs to be confirmed in future studies, but does provide evidence
as to the benefit of having strong quadriceps muscles in patients
with knee OA. “Our findings, which also include an association
of greater quadriceps strength with less knee pain and physical
limitation over followup, suggest that greater quadriceps strength
has an overall beneficial effect on symptomatic knee OA,”
the authors state. This effect may be due to a strengthening of
the vastus medialis obliquus (a quadriceps muscle that pulls the
kneecap inward), that may stabilize the kneecap and help prevent
cartilage loss behind part of the knee cap.
Although the study did not involve exercise training to strengthen
the quadriceps, there have been several short-term studies that
show that improving quadriceps strength has a beneficial effect
on knee pain and function. “While our findings suggest that
maintaining strong quadriceps is of benefit to those with knee
OA, further work is needed to determine the type and frequency
of exercise regimen that will be both safe and effective,”
the authors conclude.
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