Question: Is malalignment associated with the development of
osteoarthritis of the knee?
Design: Cohort population-based study.
Setting: Rotterdam, The Netherlands.
Patients: 1501 participants (3002 knees) =55 years of age (mean
age, 66 y; 60% women) were randomly selected from 3585 participants who
completed 6.6 years of follow-up. Of the 3002 knees, 2664 had legible
radiographs.
Assessment of risk factors: Knees were categorized as having normal
alignment (medial angle formed by the femur and tibia [FT angle] = 182° to
184°), varus alignment (FT angle <182°), or valgus alignment (FT
angle >184°).
Main outcome measures: Osteoarthritis of the knee (confirmed by
Kellgren-Lawrence radiographic score). Two readers who were blinded to the
clinical status of patients assessed the radiographs of the knee.
Main results: At baseline, 2290 knees showed no osteoarthritis
(Kellgren-Lawrence score <2). Of those, 892 knees (39%) had normal
alignment, of which 35 (3.9%) had development of osteoarthritis of the knee.
579 knees (25%) had varus alignment, of which 43 (7.4%) had development of
osteoarthritis of the knee. 819 knees (36%) had valgus alignment, of which 45
(5.5%) had development of osteoarthritis of the knee. Participants with varus
alignment had a greater risk of the development of osteoarthritis of the knee
than did participants with normal alignment; participants with valgus
alignment did not have a significantly higher risk of the development of
osteoarthritis of the knee (Table). When participants were stratified by body
mass index, varus alignment was associated with a higher risk of knee
osteoarthritis in overweight participants (odds ratio [OR] = 2.02; 95%
confidence interval [CI], 1.07 to 3.84) and obese participants (OR = 5.06; CI,
1.71 to 14.94). Valgus alignment was associated with a higher risk of knee
osteoarthritis in obese participants (OR = 3.25; CI, 1.14 to 9.27).
Conclusion: Participants with varus knee alignment (FT angle
>184°) were at higher risk for the development of osteoarthritis of the
knee.
The study by Brouwer and colleagues investigates risk factors for the
development of osteoarthritis of the knee and for progression of
osteoarthritis in >1000 patients over the medium term (about 6 years). The
authors used a practical radiographic measure on the anteroposterior
radiograph—the medial angle formed by the femur and the tibia. Although
this measure is not how most orthopaedic surgeons think of alignment, it can
easily be translated into more commonly used terms. Whereas most orthopaedic
surgeons have thought of normal alignment as 3° to 9° of valgus, varus
alignment was defined in this study as any knee with <2° of valgus
angulation, and valgus alignment was defined as any knee with >4° of
valgus angulation. The authors did not distinguish between mild valgus and
more severe valgus deformity. Nevertheless, they found that the presence of
varus malalignment influenced the development of osteoarthritis. On the other
hand, the presence of valgus malalignment did not increase the risk of the
development of osteoarthritis or worsening of the osteoarthritis in previously
mildly osteoarthritic knees. However, if being overweight is defined as having
a body mass index that is between 25 and 30 kg/m2 and being obese
is defined as having a body mass index that is >30 kg/m2, both
varus and valgus aligned knees were associated with a higher risk of the
development of osteoarthritis in obese patients than were knees in normal
alignment.
A shortcoming of this study was that previous injuries or meniscectomies
might have led to the varus malalignment. It is impossible to determine
whether these events led to the varus malalignment and, in turn, to the
development or worsening of osteoarthritis or whether pre-existing
malalignment was the culprit. Regardless, this information is of value to
practicing physicians because it allows them to counsel patients
appropriately. Whether weight loss or maneuvers that off-load the joint (such
as off-loader braces and realignment) prevent the onset of osteoarthritis is
not answered by this study.