There is evidence that muscle dysfunction is involved in the pathogenesis of knee OA2, 11). Because the lower limb musculature is the natural brace of the knee joint, important
muscle dysfunction may arise from either quadriceps
weakness or weakness of the hamstrings relative to the
quadriceps, which is usually assessed by the quadriceps:
hamstring (Q:H) ratio2, 12, 13). Thus, evaluation of muscle
dysfunction in relation to the knee joint should examine the
strength of both the quadriceps and hamstring muscles as
well as the balance of muscle strength13).
Because there is no cure for OA, treatments currently
focus on the management of symptoms. Pain relief, improved
joint function and joint stability are the main goals
of therapy. Studies conducted in recent years have provided
data that support the hypothesis that muscle weakness and
muscle atrophy contribute to the disease process14). Thus,
rehabilitation and physiotherapy are often prescribed with
the intention of alleviating pain and increasing mobility.
However, because exercise must be performed on a regular
basis to counteract muscle atrophy, continuous exercise
programs are recommended for individuals with degenerative
joint disease. Therapeutic exercise regimens either focus
on muscle strengthening and stretching exercises, or on
aerobic activities that may be land or water based.
Several muscle groups support the knee. The two main
muscle groups that control knee movement and stability
are the quadriceps and the hamstrings. The quadriceps and
hamstring muscles have the potential to provide dynamic
frontal plane knee stability because of their abduction and/
or adduction moment arms15). Using a neuromuscular biomechanical
model, the quadriceps and hamstring muscles
not only have the potential to support frontal plane moments
but also provide support to abduction-adduction moments16).
In the frontal plane, balanced co-contraction of the
quadriceps and hamstring muscles leads to increased joint
compression, which should assist in knee joint stabilization17).
The diminished co-activation of the quadriceps and
hamstrings in women may contribute to greater knee joint
instability in women than in men.
The strength relationship between the quadriceps femoris
and hamstring muscles has been measured and reported
by various researchers18–21). The isokinetic H:Q ratio for
apparently healthy subjects has been reported to be 1.70:1
and 1.37:1 at 60°/s and 180°/s angular velocities of limb
movement, respectively. The mean isometric Q:H ratio was
found to be 1.43, a value below the ratio reported for young
healthy adults (whose isometric Q:H ratio is 2:1); therefore,
the Q:H ratio is different in OA due to the relatively greater
weakness of the quadriceps femoris muscle19, 22, 23).
The purpose of the present study was to assess the effect
of hamstring and quadriceps strengthening exercises on the
activities of daily living of patients with knee OA.