Extract
Many patients inquire if they will be able to kneel after total knee
arthroplasty. We have cautioned patients regarding issues related to the
patella that are associated with kneeling, yet, despite discomfort, many
continue to kneel during various activities around the home or for religious
reasons. While new high-flexion knee implant designs allow patients to get
lower to the ground, the acts of cleaning a floor, gardening, exercising, and
kneeling in prayer require bending down on both knees, and patients often
state that they cannot kneel after total knee arthroplasty because of pain or
that they do not attempt to kneel because the position feels awkward. Kneeling
is part of daily life in certain cultures and, as elderly patients are more
active, it is becoming an activity of increasing interest. Kneeling can be
divided into three positions: kneeling at <90° (for example, while
praying on a riser in a place of worship), kneeling at 90° (for example,
while gardening or scrubbing a floor), and kneeling at full flexion (for
example, while praying on the floor).
Many patients inquire if they will be able to kneel after total knee
arthroplasty. We have cautioned patients regarding issues related to the
patella that are associated with kneeling, yet, despite discomfort, many
continue to kneel during various activities around the home or for religious
reasons. While new high-flexion knee implant designs allow patients to get
lower to the ground, the acts of cleaning a floor, gardening, exercising, and
kneeling in prayer require bending down on both knees, and patients often
state that they cannot kneel after total knee arthroplasty because of pain or
that they do not attempt to kneel because the position feels awkward. Kneeling
is part of daily life in certain cultures and, as elderly patients are more
active, it is becoming an activity of increasing interest. Kneeling can be
divided into three positions: kneeling at <90° (for example, while
praying on a riser in a place of worship), kneeling at 90° (for example,
while gardening or scrubbing a floor), and kneeling at full flexion (for
example, while praying on the floor).
Several
studies1,2
have evaluated mechanical foot stresses to improve footwear design and
comfort. The Apex Harris Mat (Aetrex, Teaneck, New Jersey) captures a dynamic
pressure print of the foot, with areas of highest pressure clearly identified.
When a load is applied to the mat, ink will be deposited at the locations of
highest pressure because all layers of the mat are compressed by the applied
load. This information can be used to prevent harmful in-shoe conditions and
can allow clinicians to provide better health care for patients with
peripheral
neuropathies1. We
applied this technology to healthy volunteers and patients to determine
high-stress areas during kneeling and created a pressure imprint of the knee
that we called a kneelprint. We hypothesized that the location of the
total knee arthroplasty incision might be a major contributor to discomfort
during kneeling, so we modified the incision to avoid areas of kneeling stress
and determined if this location resulted in more comfort for patients who
desire to kneel.
Initially, a negative image was created by applying a wet stain to the knee
of a healthy volunteer prior to kneeling. This image demonstrated the exact
areas that would require mapping (Fig.
1). Ten healthy volunteers and one patient who had had a total
knee arthroplasty one year previously were asked to kneel down on an Apex
Harris Mat (Aetrex)3
with simultaneous pressure applied to both knees
(Fig. 2). This imprinter
produced a weight-bearing image of the anterior aspect of the knee
(kneelprint), thereby demonstrating pressure-disbursement points.
An additional institutional review board-approved study included a
prospective sample of twenty-five healthy volunteers (fifty knees) (nine of
whom also had the Harris mapping), four patients who had undergone total knee
arthroplasty one to three years previously, and one patient who was evaluated
both before and after total knee arthroplasty, all of whom were asked to kneel
down with assistance on Pressurex Ultra Low (28-85 PSI) tactile
pressure-indicating film (Sensor Products, Madison, New Jersey) that was
placed on a consistent hard-floor surface
(Fig. 3). Each participant was
asked to face forward and upright without using hand support for nine seconds.
One knee at a time was measured at each trial. Temperature, time, and humidity
were recorded for each trial and were entered into the Topaq Pressure Analysis
System flatbed scanner (Sensor Products) for analysis.
Nine of the healthy volunteers who were evaluated with the Apex Harris Mat
were also evaluated with Pressurex Ultra Low (28-85 PSI) tactile
pressure-indicating film (Fig.
4).
Radiographs of the knees of one male patient were made three months after
bilateral total knee arthroplasty to evaluate kneeling
(Fig. 5).
In May 2006, the senior author (W.M.G.) modified his traditional midline
total knee arthroplasty incision by moving it medially to avoid pressure areas
identified during the kneeling process. By the end of 2006, this surgeon had
performed this incision during the treatment of 281 consecutive knees in
non-obese patients. The incision started 2 to 3 cm medial to the tip of the
tibial tubercle, lined up just medial to the medial edge of the patella. At
the top of the patella, the incision was gradually angled laterally toward the
quadriceps tendon. The incision was lengthened along the midline if excessive
tension was observed in the skin. The capsular incision was made along this
same path. At the top of the patella, a 5-mm cuff of quadriceps tendon was
created and the incision was extended 1 to 2 cm and then into the vastus
medialis. The patella was everted, and the knee was flexed
(Fig. 6).
Both the Apex Harris Mat and the pressure-indicating film usually
identified two distinct areas of high stress on the kneelprint. One was
located over the tibial tuberosity, and the other was located over the middle
of the patella. The intensity of the stress most often varied over the
tuberosity, where the presence of more body fat or rotation of the leg changed
its location or intensity (Fig.
7).
Postoperative assessment of the total knee replacements revealed that all
implants were within an acceptable range of alignment, with the femoral
component in 5° to 7° of valgus and the tibial component at 90° to
the long axis of the tibia.
Pressure-film evaluation revealed the two distinct areas of stress in most
knees, but some knees had no pressure points; this lack of pressure points
appeared to be caused by fat distribution throughout the kneeling areas,
particularly in obese patients who tended to have large fat deposits medially
or a bulging intra-articular fat pad. In thin patients, the tibial tuberosity
and the proximal crest of the tibia were consistently most prominent. As the
patient or healthy volunteer leaned forward, distinct areas of pressure over
the patella developed. When the total knee arthroplasty incision was located
more medially (Fig. 8), most
patients found little discomfort when kneeling one year after surgery.
Published studies have indicated that many patients cannot attempt or do
not feel comfortable attempting to kneel because they are worried that
kneeling will cause
injury3-7.
Palmer et al. studied seventy-five patients (100 knees) at least six months
after surgery4. The
investigators asked patients to comment on and demonstrate kneeling.
Sixty-four knees were in patients who were able to kneel without discomfort or
with mild discomfort, and twelve of the remaining knees were in patients who
were unable to kneel because of problems not related to the knee. Twenty-four
knees were in patients who were unable to kneel because of discomfort in the
knee. There was no difference between the two groups with regard to overall
knee scores, range of movement, and the presence of patellar resurfacing.
Schai et al. questioned patients about their ability to kneel and their
perception of factors affecting this ability after total knee
arthroplasty8.
Seventy patients (100 knees) were asked to comment on their ability to kneel.
The investigators found that the patients' perceived ability to kneel after
total knee arthroplasty was less than their observed ability. In patients who
had observed difficulty in kneeling, scar pain and back-related problems
seemed to be the major limitations.
Hassaballa et al. studied 253 knees that were treated with total,
unicompartmental, or patellofemoral knee replacement and analyzed kneeling
preoperatively and at one and two years postoperatively with the use of a
kneeling
score9,10.
In all three groups, kneeling ability was poor before surgery and improved
after surgery. Kneeling ability was best in the unicompartmental group and
worst in the patellofemoral replacement group. The investigators concluded
that kneeling ability in osteoarthritic patients is poor but improves after
knee arthroplasty; however, the majority of these patients will still have
difficulty
kneeling9. In a
separate study, Hassaballa et al. also found that patient-centered
questionnaires do not accurately document a patient's ability to kneel after
surgery10.
Prior to the use of the new medial incision, our patients who demonstrated
kneeling stated that the anterior scar was either painful or "felt
funny." The sensation of "feeling funny" may be attributed
to the numbness that remains following an injury to the recurrent branch of
the saphenous
nerve11. The knees
were usually tender to palpation over the tuberosity. With the medial
incision, most patients did not complain of pain on kneeling and did not have
tenderness over the tibial tuberosity.
Pain with kneeling may also be attributed to factors other than the
incision. If there is flexion instability with posterior subluxation, kneeling
may cause pain as the tibia is forced posteriorly and the femur moves
anteriorly. This was unlikely in our patients because of the congruency of the
components and the substantial lip of the tibial component
(Fig. 5). Pain may also be
caused by the host patella flexing over the component. This happens if the
resection has been too aggressive, leaving a thin, flexible host patella.
Danger to the patellar prosthesis during kneeling requires additional
study. There are potential issues related to patellar loosening or host-bone
fracture that have not yet been elucidated. Because kneeling is likely to be
an intermittent activity, we will continue to accommodate the desires of our
patients and perform the medial midline incision, placing it medial to the
highest stress points documented in the kneeling pressure studies. ?
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