1. The Journal of Arthroplasty Vol. 21 No. 1 2006
Predictive Risk Factors for Stiff Knees in
Total Knee Arthroplasty
Rajiv Gandhi, MD,* Justin de Beer, MD, FRCSC,*y James Leone, MD, FRCSC,*
Danielle Petruccelli, MLIS,y Mitchell Winemaker, MD, FRCSC,*y and
Anthony Adili, MD, PEng, FRCSC*z
Abstract: Retrospective review of 1216 primary total knee arthroplasties (TKAs) to
evaluate incidence and predictors of arthrofibrosis, defined as flexion less than 908
1 year post-TKA. Incidence of stiffness post-TKA was 3.7% (45/1216). A matched
case-control study was then conducted to identify predictive factors for this
outcome. Preoperative flexion and intraoperative flexion were predictive of
ultimate postoperative flexion ( P = .001 and P = .039, respectively). There was
no correlation between postoperative stiffness and specific medical comorbidities,
including diabetes. Preoperative and postoperative relative decreased patellar height
and stiffness postoperative were significantly correlated ( P = .001). Although
stiffness post-TKA is multifactorial, careful attention to surgical exposure, restoring
gap kinematics, minimizing surgical trauma to the patellar ligament/extensor
mechanism, appropriate implant selection, and physiotherapy combined with a
well-motivated patient may all serve to reduce the incidence of stiffness post-TKA.
Key words: total knee arthroplasty, stiffness, arthrofibrosis, outcome, range
of movement.
n 2006 Elsevier Inc. All rights reserved.
The goal of total knee arthroplasty (TKA) is to true incidence is difficult to discern from the
provide a stable painless knee with adequate range literature because of the lack of a uniform defini-
of motion for activities of daily living. Studies have tion for stiffness.
shown that 838 of flexion is required for stair As documented in the literature, stiffness after
climbing, 938 for rising from a seated position, and TKA can be attributed to poor preoperative and
1068 for shoelace tying [1]. The incidence of intraoperative range of motion [2-5], intraoperative
arthrofibrosis after TKA is generally low, but its technical problems [4,6,7], obesity [8], preoperative
varus/valgus alignment [9], and poor patient reha-
bilitation after surgery [6,7,10]. Most often, how-
ever, no cause can be identified [5,6,10]. Others
From the *Faculty of Health Sciences, McMaster University, have suggested that having diabetes may predispose
Hamilton, Ontario, Canada; yHamilton Health Sciences Henderson a patient to arthrofibrosis [11]; however, this is not
Hospital, Hamilton, Ontario, Canada, and z St. Joseph’s Healthcare
Hamilton, Hamilton, Ontario, Canada. well defined in the literature.
Submitted November 23, 2004; accepted June 9, 2005. A retrospective review of 1216 primary TKAs
No benefits on funds were received in support of the study. performed at a high-volume tertiary care orthope-
Reprint requests: Danielle Petruccelli, MLIS, Hamilton
Arthroplasty Group, Hamilton Health Sciences Henderson dic center between 1998 and 2002 was conducted
Hospital, 711 Concession St., Hamilton, Ontario, Canada to identify the incidence of and predictive factors
L8V 1C3. associated with knee flexion less than 908 at 1 year
n 2006 Elsevier Inc. All rights reserved
0883-5403/06/1906-0004$30.00/0 after TKA. The average progression of knee flexion
doi:10.1016/j.arth.2005.06.004 within the first year after TKA was also evaluated to
46

2. Predictive Risk Factors for Stiff TKA ! Gandhi et al 47
Table 1. Baseline Characteristics All surgeries used a standard midline incision
with medial parapatellar arthrotomy for exposure
SG (SD) CG (SD)
(n = 45) (n = 45) P of the knee. All posterior osteophytes were re-
moved and soft tissue release was performed as
Age 67.7 (8.8) 67 (9.6) .667 necessary to balance the knee. All TKA compo-
Sex (M:F) 12:33 12:33 – nents were cemented.
BMI 35 (8.5) 33.1 (6.2) .271
ASA rating Patient medical records, operative notes, and
ASA 1 1/45 1/45 – radiographs were reviewed. Potential predefined
ASA 2 34/45 34/45 – predictive factors of stiffness included preoperative
ASA 3 10/45 10/45 –
Preoperative medical comorbidities, surgical skin-to-skin time,
alignment estimated blood loss, intraoperative and postopera-
Varus:valgus 35:10 31:14 .340
Mean varus 9.6 (7.4) 9.21 (6) .796
tive complications, and revision rate. Functional
Mean valgus 6.7 (2.9) 8.9 (4.2) .169 assessment, completed by a physiotherapy assistant,
Preoperative flexion 90 (21.4) 102.4 (16.6) .005 included range of motion and Knee Society Score
Preoperative KSS 30.8 (15.4) 36.2 (13.6) .112 (KSS) preoperatively and at 6 weeks, 6 months, and
Preoperative 41.2 (5.4) 41.8 (7.9) .702
Oxford Score 1 year postoperatively [13]. The clinical KSS scoring
Preoperative 1.09 (0.12) 1.16 (0.14) .025 component assesses pain, range of motion, and
patellar height stability. Patients were also asked to complete the
Preoperative 6.7 (2.7) 6.1 (2.1) .159
tibial slope Oxford Knee functional score at like intervals [14].
Radiographic analysis included tibiofemoral align-
Bold denotes statistically significant. BMI indicates body ment measured from long-leg standing radiographs,
mass index.
tibial slope, and the Insall-Salvati (IS) ratio for
patellar height [15]. The IS method has a normal
ratio of 0.8 to 1.2 with patella infra defined as a
provide some guidelines with respect to possible patella height ratio less than 0.8 and patella alta
closed/open manipulation for the treatment of defined as a patella height ratio greater than 1.2.
early postoperative arthrofibrosis. The ratio is defined as the length of the patella
ligament divided by the longest coronal length of
the patella [15].
Materials and Methods To determine statistical significance between the
two groups, paired t tests were conducted on all
A retrospective review of 1216 primary TKAs continuous variables. The v 2 or Fisher exact test,
performed for a diagnosis of osteoarthritis at a single where appropriate, was conducted on all categori-
tertiary care orthopedic center among 5 surgeons cal variables. Multiple linear regression analysis
from September 1998 to May 2002 identified 45 was also conducted to identify factors predictive of
TKAs with a 1-year postoperative flexion range of stiff TKA. P b .05 was considered statistically
less than 908. We identified these patients through significant. All statistical analyses were performed
our prospective arthroplasty database that records using SPSS version 10.
information on all patients who undergo total joint
arthroplasty at our hospital. These 45 stiff TKAs
were matched to 45 TKAs with greater than 908 Results
flexion at 1 year postoperative. Cases and controls
were matched one-to-one for age, sex, body mass The incidence of stiffness post-TKA was 3.7% (45/
index, American Society of Anesthesiologists (ASA) 1216). The stiff TKA cohort comprised 12 (26.7%)
rating [12] (as a means of classifying patients males and 33 (73.3%) females. One (2.2%) of 45
according to the extent of their systemic disease), patients was rated as ASA 1, 34 (75.6%) were rated
surgeon, implant type, and fixation. Cases and as ASA 2, and 10 (22.2%) as ASA 3 (Table 1).
controls were then assessed within a nested case- Thirty-seven (82.2%) of 45 knees in the stiff TKA
control study to determine predictive factors of stiff group (SG) were implanted with a posterior stabi-
TKA. Flexion of 908 was chosen as our definition of lized total knee and 8 (17.8%) with a cruciate-
stiffness because this would provide adequate retaining total knee. All implants were cemented.
motion for patients to perform activities of daily Three (6.7%) of 45 knees had previously undergone
living, including stair climbing and rising from a high tibial osteotomy.
seated position. All patients in both groups had a Two (4.4%) of 45 cases in the stiff TKA cohort
preoperative diagnosis of osteoarthritis. were receiving associated worker’s compensation

3. 48 The Journal of Arthroplasty Vol. 21 No. 1 January 2006
Table 2. Preoperative Medical Comorbidities Preoperative patellar height was significantly
different between the two groups with an IS ratio
SG (SD) (n = 45) CG (SD) (n = 45) P
of 1.09 (F0.12) in the SG vs 1.16 (F0.14) in the
Anemia 6.7 4.4 .5 CG. ( P = .025). Postoperative patellar height was
Angina 15.6 8.9 .334 also significantly different between the two groups
Diabetes 17.8 6.7 .108 with an IS ratio of 1.02 (F0.39) in the SG com-
Heart Disease 26.7 6.7 .011
Hypertension 51.1 53.3 .833 pared with 1.27 (F0.26) in the CG ( P = .001).
Stroke 6.7 6.7 – Although there was a significant change in IS ratio
Previous MI 11.1 0 .056 in the CG from 1.16 preoperative to 1.27 postop-
Nil 28.9 31.1 .818
erative ( P = .006), there was no significant change
Values are expressed as percentage. Bold denotes statistically in IS ratio preoperative and postoperative in the
significant. MI indicates myocardial infarction. SG ( P = .45). The number of patients with patella
infra (IS b0.8) significantly increased postoperative
in the SG from 0 of 45 patients preoperative vs
benefits as compared with 1 (2.2%) of 45 cases in 18 of 45 patients postoperative ( P b .0001). There
the control group (CG) ( P = .5). was no significant difference in the number of
The observed incidence of significant preopera- patients with patella infra (IS b0.8) preoperative
tive comorbid factors, including anemia, diabetes, and postoperative in the CG (1/45 patients
angina, heart disease, previous myocardial infarc- preoperative vs 1/45 patients postoperative; P N .05).
tion, hypertension, and stroke, among the two There was no difference between the two groups
cohorts is outlined in Table 2. Of the SG, with regard to preoperative tibiofemoral alignment
14 (31.1%) of 45 patients presented with only (Table 1) or mean postoperative valgus alignment
1 comorbidity, whereas 7 (15.6%) presented with (4.88 [F2.5] for the SG and 4.68 [F3.2] for the CG;
2 comorbidities and 11 (24.4%) with 3 or more P = .631). Both groups had a significant difference
comorbidities. Comparatively, 24 (53.3%) of in preoperative and postoperative tibial slope
45 patients within the CG presented with 1 comor- (SG: 6.7 [F2.7] preoperative vs 2.5 [F2.4] postop-
bidity ( P = .033), 5 (11.1%) with 2 comorbidities erative, P b .0001; CG: 6.1 [F2.1] preoperative vs
( P = .535), and 2 (4.4%) with 3 or more comorbid- 2.0 [F2.6] postoperative, P b .0001). However,
ities ( P = .007). Thirteen (28.9%) of 45 patients in there was no statistically significant difference in
the SG did not present with a preoperative comor- postoperative tibial slope between the SG and
bidity as compared with 14 (31.1%) of 45 in the CG CG ( P = .390).
( P = .818). There was no statistically significant difference in
Mean intraoperative flexion at time of wound mean KSS preoperatively (Table 1) or at 6 weeks
closure was 108.68 (F23.7) for the SG, compared
with a mean flexion of 120.48 (F7.9) for the CG
( P = .039). Mean skin-to-skin operative time was Table 3. Clinical Outcomes
81.4 minutes (F22.6) for the SG and 78.6 minutes
SG (SD) CG (SD)
(F18.5) for the CG ( P = .611). (n = 45) (n = 45) P
There were intraoperative complications associ-
ated with 3 (6.7%) of 45 knees in the SG and Flexion
1 (2.2%) of 45 knees in the CG ( P = .616). Intraoperative 108.6 (23.7) 120.4 (7.9) .039
at closure
Intraoperative complications in the SG included 6-wk 79.4 (16.9) 101.1 (10) b.0001
3 partial patellar tendon avulsions repaired with 6-mo 87.5 (12.9) 110.1 (10.3) b.0001
corkscrew suture anchors. Given that the SG had 1-y 80.2 (13.4) 111 (7.5) b.0001
KSS
poor preoperative range of flexion, intraoperative 6-wk 69.2 (17.8) 77.8 (17.4) .106
exposure was in general more difficult to achieve, 6-mo 77.1 (14.4) 86.7 (16.1) .05
thus explaining the increased incidence of patellar 1-y 75.7 (16.6) 85 (15.9) .014
Oxford Knee
tendon avulsion. The intraoperative complication in Score
the CG was a proximal tibia fracture repaired with 6-wk 36.5 (6.9) 31.8 (8.6) .040
2 screws. All complications resolved uneventfully. 6-mo 30.3 (9.2) 28.1 (10.2) .331
1-y 29.2 (9.8) 27.9 (9.7) .519
Mean knee flexion at all intervals observed, Postoperative 1.02 (0.39) 1.27 (0.26) .001
including preoperative (Table 1), intraoperative at patellar height
time of wound closure, 6 weeks, 6 months, and Postoperative 2.5 (2.4) 2.0 (2.6) .390
tibial slope
1 year, was significantly different between the two
groups (Table 3). Bold denotes statistically significant.

4. Predictive Risk Factors for Stiff TKA ! Gandhi et al 49
and 6 months postoperatively. However, 1-year flexion less than 758. Previous authors have
postoperative KSS was significantly different be- reported incidence of stiff and painful knee as high
tween the SG with a mean score of 75.7 (F16.6) as 8% to 12% [11]. We found an incidence of 3.7%
and the CG with a mean score of 85 (F15.9) at 1 year where stiffness was defined as flexion less
( P = .014) (Table 3). than 908. The decreased incidence of stiffness may
Mean Oxford Score was significantly different be- be due to improved prosthetic design, improved
tween the SG and CG at 6 weeks postoperative (36.5 instrumentation allowing more reproducible align-
[6.9] and 31.8 [8.6], respectively; P = .040) (Table 3). ment, improved understanding of soft tissue and
Two (2.2%) of 45 patients in the SG experienced gap balancing, and a greater variety of implant sizes
early postoperative complications, including to best match the patient’s native anatomy.
1 patient who had a bleed into the operative leg There was a trend signifying an increase in
at 10 days postoperatively and 1 patient who technical difficulty in the SG in our study. Most
developed a surgical wound infection. Similarly, significantly, we observed several patellar ligament
2 (2.2%) of 45 patients in the CG had postoper- avulsions and an increased operative time in the
ative complications including 1 patient who de- SG. Furthermore, we found that the SG had a
veloped an Escherichia coli infection in both the significantly decreased flexion range of movement
blood and urine 3 weeks postoperatively, but (ROM) against gravity at the end of the operative
without involvement of the knee arthroplasty. procedure compared with the CG. This may be a
An additional patient had a wound infection reflection of a preoperatively contracted extensor
8 months postoperatively after a blow to the knee mechanism or difficulty in achieving proper gap
with deep infection secondary to posttraumatic kinematics in this subgroup of patients.
hemarthrosis ultimately requiring removal of the Many previous authors have looked at identify-
TKA components with subsequent TKA revision at ing predictive factors for arthrofibrosis after TKA.
11 months postoperatively. All remaining compli- Ritter et al [4] identified preoperative flexion as
cations resolved uneventfully. the principal predictive factor of postoperative
Three (6.7%) of 45 TKAs in the SG required ROM. This finding has also been confirmed by
revision, including 1 TKA revision for stiffness numerous other authors [2,3,5]. The more limited
23 months postoperatively and 2 TKAs for aseptic the preoperative ROM, the greater the likelihood
failure at 22 and 29 months post–primary TKA. that the associated stiffness of the extensor mech-
Likewise, there were 3 (6.7%) reoperations in anism may contribute to limited flexion after
the CG including 2 TKA revisions for aseptic surgery. Further studies have also identified intra-
failure at 9 and 25 months, respectively, and 1 for operative ROM [19], preoperative varus/valgus
infection at 9 months post–primary TKA as tibiofemoral angle [9], preoperative diagnosis
indicated previously. [20], body weight [8], surgical closure [21], and
Multiple linear regression analysis revealed that type of implant [22] as predictive factors for a stiff
preoperative flexion and flexion at time of surgical TKA. We found that preoperative, intraoperative,
closure and 6 weeks and 6 months postoperatively 6-week, and 6-month flexions are all predictive of
were predictive of stiff TKA at 1 year. Likewise, a stiff knee at 1 year postoperatively.
patellar height as determined at 1 year by the IS The issue of patella infra limiting flexion in TKA
ratio was also predictive of a stiff TKA ( P = .001). has been well established particularly with TKA
after closing wedge high tibial osteotomy [23]. The
patella can be relatively low lying secondary to
Discussion joint line elevation or from scarring and subsequent
shortening of the infrapatellar tendon [24]. Figgie
Knee flexion after TKA correlates closely with et al [7] found that joint line elevation greater than
patient satisfaction and function [16]. The inci- 10 mm in a posterior stabilized knee limits flexion,
dence of stiffness after TKA varies based on the whereas Shoji et al [8] showed the same result with
definitions used. Scranton [17] defined stiffness as 16 mm of joint line elevation. Schurman et al [25],
flexion less than 858; Christensen et al [6] defined it however, looked at the distance from the patella to
as an arc of motion less than 708; and Nicholls and the joint line and found no correlation between
Dorr [18] defined it as flexion contracture greater this value and the flexion outcome at 1 year. Our
than 208 or a total range of motion less than 458. study found a significantly lower patellar height
Kim et al [10] reported an incidence of 1.3% at a between the SG and CG preoperatively and post-
mean follow-up of 32 months where stiffness was operatively. Furthermore, the SG experienced a
defined as flexion contracture less than 158 and/or significant decrease in the IS ratio postoperatively,

5. 50 The Journal of Arthroplasty Vol. 21 No. 1 January 2006
whereas the CG displayed an increase in the IS flexion over the next 6 months. Based on these
ratio postoperatively. There was a significantly findings, patients with preoperative stiffness need to
greater number of patients with true patellar infra be counseled that postoperative range of motion
(IS b0.8) in the SG compared to the CG postoper- may not significantly improve post-TKA. Further-
atively (18/45 in the SG vs 1/45 in the CG). We feel more, range of motion at 6 months post-TKA may
that the increased difficulty in exposure associated represent the maximum flexion arc one can expect
with a stiff knee may require a more aggressive despite further nonoperative measures.
resection of the fat pad and greater traction on the The options for management of the stiff total knee
already relative short patellar tendon resulting in include aggressive physiotherapy, closed manipula-
the potential for increased scarring and shortening tion F arthroscopic lysis of adhesions, posterior
of the patellar tendon postoperatively. Conse- cruciate ligament recession or resection, open
quently, scarring of the infrapatellar tendon from debridement, or revision surgery [5,6,10,11]. There
aggressive resection of the fat pad or elevation of is no consensus in the literature as to the optimal
the joint line may contribute to stiffness post-TKA. timing for closed manipulation of a stiff total knee.
These findings suggest that the SG developed Brassard and Scuderi [30] recommended manipu-
scarring and/or true shortening of the patellar lation if ROM is less than 758 by 6 to 12 weeks and
tendon when compared with the CG. Moreover, Scranton [17] recommended manipulation if flex-
relative patella infra preoperatively was also found ion is less than 908 at 6 weeks, whereas Fox and Poss
to correlate with poor postoperative range of [31] recommended manipulation by 2 weeks if
motion and stiffness at 1 year. Although an IS ratio ROM is less than 908. Given our findings that stiff
of 1.02 in the SG postoperative does not represent TKA patients experience improvement in their
patellar baja by the IS definition, one must keep in average ROM at 6 weeks with a plateau in knee
mind that the normal values after TKA have not flexion reached at 6 months postoperatively, we
been established. As such, we concluded that the suggest that closed manipulation be considered for
relative patellar height difference between the two those patients with flexion less than 808 before
groups was still an important finding. 10 weeks, as there is no advantage to the patient in
Diabetes mellitus has been suggested as a risk delaying this intervention further. The patient with
factor for arthrofibrosis after TKA [11]. Others have less than 908 flexion at 6 months will not benefit
shown increased rates of infections, both superficial from observation alone, but rather warrants consid-
and deep, as well as higher revision rates in those eration for surgical intervention. Babis et al [5]
with diabetes [26-28]. Our study did not identify reviewed the Mayo Clinic experience with arthrol-
any medical comorbidities to be associated with ysis of adhesions and tibial liner exchange to a
limited flexion at 1 year, including diabetes. thinner polyethelene and found no benefit to this
However, it was noted that the SG had a signifi- intervention and do not recommend its use for the
cantly higher number of preoperative comorbidities management of a stiff total knee. Christensen et al
per patient as compared with the CG. This may [6] reported excellent results after full revision of
suggest some form of intrinsic systemic predisposi- stiff TKAs having less than 708 arc of motion at an
tion to scar tissue formation. Further analysis average of 37 months of follow-up.
revealed that this difference was largely attribut- The stiff TKA represents a particularly difficult
able to preexisting cardiac disease. This, in our challenge to the arthroplasty surgeon. Maximizing
opinion, more strongly suggests severe preopera- patient knee ROM preoperatively with physiother-
tive deconditioning, which may in turn compro- apy would be well served based upon our findings
mise the physical ability of the patient to fully and those of other investigators [2-5,19]. However,
participate in the routine postoperative rehabilita- this recommendation should be individualized as
tion protocol, thus negatively impacting ultimate some patients may find that aggressive preoperative
range of motion achieved. physiotherapy may exacerbate their overall level of
Many authors have previously described maxi- symptoms. Furthermore, patients with preoperative
mal flexion being obtained at 1 year [3,29], whereas comorbidities that may affect their ability to partic-
Ritter et al [4] showed that there was only a 2.88 ipate fully in a postoperative rehabilitation program
increase in flexion in their patients from the may benefit from preoperative counseling and an
6-month mark to 3 years. From our study, we appropriately modified rehabilitation program.
found that ROM continued to improve in all However, further study is required to fully address
patients until the 6-month follow-up visit, after this issue. More specifically, patients with preoper-
which time, the SG lost an average of 7.38 of flexion, ative relative patella infra are at an increased risk of
whereas the CG gained an average of only 0.98 of developing stiffness by 1 year postoperatively.

6. Predictive Risk Factors for Stiff TKA ! Gandhi et al 51
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