Osteoarthritis (OA), a
degenerative joint disease, is a complex condition affecting the cartilage as
well as other elements of the joint structure. The condition is associated with
joint pain and disability. When osteoarthritis becomes severe, total knee
replacement (TKR) is done to improve pain and function of the affected joint.
Prior to TKR, women generally
report higher pain intensity at rest and greater perceived functional deficits
than men. They also perform worse than men on function measures such as the
6-minute walk and other tests. However, differences in pain sensitivity, pain
during function, psychosocial variables, and physical activity levels in late
stage osteoarthritis have still not been successfully determined.
Therefore, Shalome Tonelli and
colleagues from the University of Iowa, USA, undertook a study to examine the
differences in pain, pain sensitivity, function, psychosocial variables, and
physical activity between women and men with knee osteoarthritis immediately
prior to total knee replacement.
A total of 138 women and 70 men
with knee osteoarthritis immediately prior (1 week) to total knee replacement
surgery were selected for the study. Information regarding gender, age, race,
marital status, education, income, duration of knee pain, OA grade
(Kellgren-Lawrence), pain or OA in the contralateral knee, height and weight,
and analgesia intake was collected. Assessment included the following:
Pain was assessed using self-report measures (Brief
Pain Inventory (BPI), Knee Injury and Osteoarthritis Outcome Score (KOOS),
Short-Form 36 (SF-36)) and with a 0 to 20 numerical rating scale (NRS) at rest
and during function tests.
Pain sensitivity was assessed
using quantitative sensory measures, including pressure pain thresholds, heat
pain thresholds, and heat tolerance.
including depression (Geriatric Depression Scale), anxiety (State Trait Anxiety
Inventory), pain catastrophizing (Pain Catastrophizing Scale), and social
support (Social Provisions Scale), were assessed.
Function was assessed with
self-report measures (KOOS, SF-36), specific function tasks (timed walk,
maximal active flexion and extension).
Physical activity was measured
using accelerometer (average metabolic equivalent tasks (METS)/day and average
Results clearly showed a gender
Women had significantly higher pain intensity (7.34 ± 5.69) than
men (5.69 ± 4.95) during the gait speed
test as well as during active knee extension (women 8.40 ± 6.43 and men
5.93 ± 5.44). However, pain at rest did not vary significantly between women
and men with the average resting pain measuring 3.77 ± 4.37 and 2.67 ± 3.81,
Although women had
significantly worse pain and more impaired function than men, their actual
physical activity levels (accelerometry) did not significantly differ and their
OA grade was significantly lower, that is, less severe.
Women had more deficits on
self-reported function on the SF-36 PF subscale and KOOS ADL subscale when
compared to men, which means, women had
reduced ability to perform the gait speed test and reduced knee active range of
motion. The researchers think that the functional differences in knee OA
subjects may in part be due to differences in quadriceps muscle strength
between women and men.
Regarding pressure pain
thresholds, there was a greater mechanical
pain sensitivity of the deep tissue in women when compared to men when a
chronic pain condition such as OA is present.
On the psychosocial level, scores were similar between women and men
for depression, state anxiety, trait anxiety, pain catastrophizing, and
perceived social support. Around 15 percent of both women and men screened
positive for depression. Researchers think that depression explains a portion
of physical activity levels in people with late-stage OA. Thus, 'depression may
be related to not only pain, but also function in people with OA', they reason.
'Our results clearly show that women have greater pain, greater pain
sensitivity, and reduced function when compared to men. The role of sex
needs to be further examined to determine if these pain differences are due to
hormonal differences, socialization, or other factors', concluded the authors.
They further recommended that treatments should place a greater emphasis on
pain management and improving function, particularly in women with osteoarthritis.
Tonelli SM, Rakel BA, Cooper NA, Angstom WL,
Sluka KA. Women with knee osteoarthritis have more pain and poorer function
than men, but similar physical activity prior to total knee replacement. Biol
Sex Differ. 2011 Nov 10;2:12.