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13 Hip Osteoarthritis andArthroplasty
345
strand. This logic applies to cross-linked polyethylene. The wear rate is reduced by tenfold and the
debris produced is of much smaller particles
(Fig.13.19).
In order to reduce particle wear seen with
polyethylene liners, two other alternatives were
developed. These, however, have fallen out of
favor given the excellent wear properties of
newer highly-cross-linked polyethylene. These
are referred to as hard-on-hard interfaces, metalon- metal and ceramic-on-ceramic. By using
much harder materials for the articulation, the
wear rate and debris production can be reduced
by up to 1000-fold. These articulations, however,
a
b
Fig. 13.19 (a) Anteroposterior radiograph of the left hip
of a patient immediately post-operatively after a noncemented total hip arthroplasty compared to (b
operatively demonstrates a markedly eccentric position of
the femoral head within the acetabular component. The
blue line demonstrates the original center of the femoral
neck in relation to the acetabulum from post-op compared
to 2years. (From Knox, D., Hamilton, S.W., Wardlaw, D.
etal. Early catastrophic acetabular failure in Furlong total
hip replacements. J Orthopaed Traumatol 10, 39–42 (2009).
https://doi.org/10.1007/s10195- 008- 0045- z. Reprinted
with permission)
) 2-year post-
also have some limitations. Metal on metal
involves the use of a cobalt–chromium femoral
head on a cobalt–chromium acetabular liner. This
articulation has been in clinical use for approximately 30years. Early designs failed early due to
design problems. The early heads were made of
equal dimension to the acetabular opening, which
would result in binding of the head within the
acetabulum and the component would loosen.
Current designs have slightly reduced the size of
the head relative to the acetabulum. This allows
for lubrication of the interface and less friction.
However, metal debris is produced in the form of
small metal ions which are detectable in the
blood, lymphatics, and urine of patients with
metal-on-metal hip articulations. The long-term
effects of this are unknown, but there is a concern
since the ions continue to be produced over the
entire life of the joint replacement. These
implants are contraindicated for women of childbearing age and patients with renal failure for this
reason. The metal-on-metal bearing surface also
has the advantage of using very large femoral
head designs which can improve stability and
range of motion by increasing the head to neck
ratio and maximizing the jump distance necessary for the head to dislocate. Many surgeons
allow patients to participate in higher impact
activities with hard-on-hard bearing surface
implants. However, recent problems have begun
to appear with patients developing painful hips
and no evidence of gross loosening. Patients can
also develop a pseudotumor in response to metal
particles or issues with their abductors. A pseudotumor is a large, solid, or semi-liquid mass of
soft tissue that grows around the hip joint. It is
thought that some patients develop hypersensitivity to metal debris particles, leading to pain and,
in some cases, signicant synovitis. Early investigation suggests that a vertical placement of the
acetabular component can lead to edge loading
and subsequent increase of wear debris. Further
studies are needed to help clarify the situation.
Ceramic-on-ceramic is the other hard on hard
interface and results in the least amount of wear
debris of all the currently used articulations for
total hip arthroplasty. However, it is limited by
the strength of the ceramic material. Ceramic
346
G. Perraut et al.
implants can be prone to fracture and when a
ceramic implant fails, it results in a catastrophic
failure. The ceramic fragments are very hard and
abrasive, resulting in rapid extensive wear of the
metallic implants that are attached to the bones.
Frequently, the metal components attached to the
bones and the ceramic articulation all need to be
removed after a fracture. The remaining particles
in the soft tissue surrounding the joint lessen the
success rates of revision surgery after ceramic
fracture. A phenomenon of “squeaking” has also
been reported in which patients develop audible
squeaking when actively moving their hip
replacement. It is thought that improper placement of the components increases the likelihood
this problem and can require revision surgery.
Wear and loosening are worrisome complications, which are being addressed by improvements in materials and designs. However, the
current devices have such high success rates that
determining if new technologies are truly an
improvement will need at least 10years of clinical follow-up. All the new devices need to be
evaluated not only for their benets but also for
the real and potential limitations.
Complications
The most frequent complication after THR is
thromboembolic disease (TED). This includes
deep venous thrombosis (DVT) and pulmonary
embolism. Early in the history of THR, the rate of
fatal pulmonary embolism was 1–2%. However,
at that time patients were kept on bed rest for as
long as 2–3weeks and kept up to 6weeks in the
hospital. Early mobilization of patients has
undoubtedly contributed to the signicant reduction in the rate of fatal pulmonary embolism.
However, signicant reduction has also occurred
through the use of anticoagulant prophylaxis,
regional anesthesia, shorter operating times, and
lower blood loss. In the USA, THR is considered
a signicant risk factor for TED and therefore the
routine use of medical and/or mechanical prophylaxis has been recommended. At present, the
rate of TED ranges between 5% and 20%. The
rate of fatal pulmonary embolism is low, approxi-
mately 0.01%. The principal methods of prophylaxis are low-dose Coumadin (warfarin), aspirin,
low-molecular weight heparin, and pneumatic
compression stockings.
Aspirin has been used for DVT prophylaxis
historically and has gained popularity for use
after joint replacement. Aspirin irreversibly
inhibits platelet function and theoretically will
reduce the rate of formation of DVT. Multiple
studies have examined the effectiveness of aspirin for DVT prophylaxis after total joint replacement. Aspirin has been demonstrated to be
equally as effective as multiple other pharmacologic anti-coagulants, including low-molecular
weight heparin, rivaroxaban, and enoxaparin.
Hypotensive epidural anesthesia (HEA) is an
excellent anesthesia technique for THR; however, it requires careful patient monitoring and a
dedicated anesthesia team. This form of anesthesia results in reduced blood loss while maintaining blood ow in the lower extremities. This
reduces the need for transfusion post-operatively,
which has been shown to increase the risk of
DVT. In addition, the reduction in blood loss
results in less activation of the coagulation cascade, again minimizing the risk of DVT. While
this technique has been shown to be very effective, it has not been widely applied due to concerns about the reduction of mean arterial
pressure in elderly patients, which may result in
stroke, renal failure, or myocardial infarction.
Dislocation of the prosthetic femoral head
from the acetabular component occurs in 1–3%
of patients after THR. Post-operatively patients
are instructed to not bend their replaced hip
beyond 90°, to keep their legs abducted and in
neutral rotation. These restrictions should be followed closely for the rst 6weeks following surgery. After this time, the patient should have
formed a sufcient pseudocapsule to protect
against dislocation. However, a replaced hip is
always at greater risk for dislocation compared to
a native hip joint. The majority of patients who
dislocate their hip in the early post-operative
period can be reduced without additional surgery
and protected with a hip abduction brace or knee
immobilizer for 6weeks to allow healing of the
pseudocapsule. In addition to patient compliance,
13 Hip Osteoarthritis andArthroplasty
347
the other etiologies for dislocation are component malposition, excessive soft tissue laxity, and
impingement of the prosthetic or osseous structures resulting in levering of the femoral head out
of the acetabulum. If a patient recurrently dislocates, revision surgery may be indicated.
The most devastating complication after THR
is prosthetic joint infection. Early post-operative
infection occurs in approximately 0.3–0.5% of
cases after primary THR.Late infection resulting
from hematogenous spread can occur in 1–2% of
patients. If detected within the rst 6weeks postoperatively, aggressive open debridement and
modular component exchange combined with
intravenous antibiotics may be successful.
However, if the infection recurs after debridement or is detected beyond 6weeks of symptoms,
treatment typically consists of a two-stage procedure. This involves the removal of the prosthetic
components and all cement if present. An antibiotic impregnated spacer is placed at the time of
explant, which provides a local depot of antibiotics at the site of the infection and improves
mobility and maintains soft tissue tension during
the treatment period. Appropriate intravenous
antibiotics are administered for 6–8 weeks and
the patient is monitored for clinical signs of
infection. If lab values normalize (white blood
cell [WBC], erythrocyte sedimentation rate
[ESR], C-reactive protein), the joint can be aspirated after antibiotics have been stopped for at
least 2weeks. If this is negative, the second-stage
reimplantation can be done. The success rate for
this technique is often greater than 90%. If the
pathologic organisms are highly virulent and
resistant to antibiotic therapy, reimplantation can
be delayed for more than 12months.
Heterotopic ossication (HO) can form
around a THR in 5–25% of cases. Heterotopic
bone is histologically bone tissue. It forms within
the muscle around the hip after arthroplasty.
There is a metaplasia that occurs, forming a bone
matrix that becomes calcied over the rst
6–12months after the surgery. Most commonly
the presence of HO will not compromise the clinical result. Associated risk factors are patients
with hypertrophic osteoarthritis, males, greater
than age 65, HO formation after previous surgery, and ankylosing spondylitis.
Heterotopic ossication is graded according
to the Brooker classication. Grade one consists
of isolated islands of bone within the soft tissue
between the femur and pelvis. Grade two is bone
protruding from the proximal femur or pelvis
with greater than 1cm of separation. Grade three
consists of bone protruding from the femur and/
or pelvis with less than 1cm between the bones.
Grade four is radiographic ankylosis, with no visible space between the bone protruding from the
femur and pelvis. Grades one and two are rarely
symptomatic. Grade three patients usually have
stiffness and mild pain. Patients with grade four
usually have marked stiffness and can be very
symptomatic (Fig.13.20).
abcde
Fig. 13.20 The Brooker classication. (a) Immediate
post-operative images. (b, c, d, e)—Grade 1 (b) through
Grade 4 (e) progression. (From Hayashi D, Gould ES, Ho
C, Caruana DL, Komatsu DE, Yang J, Zhu C, Mufti M,
Nicholson J. Severity of heterotopic ossication in
patients following surgery for hip fracture: a retrospective
observational study. BMC Musculoskelet Disord. 2019
Jul 27;20(1):348. doi: 10.1186/s12891-019-2725-7.
PMID: 31351447; PMCID: PMC6661104)
348
G. Perraut et al.
Patients who are at high risk for this complication can receive prophylaxis using indomethacin
or low-dose radiation therapy. Once HO forms,
the patients should be encouraged to maintain
range of motion and activity, but passive stretching and passive range of motion should be
avoided. Surgical intervention, in which the HO
is excised, is indicated in patients with signicant
restriction of motion and pain. This occurs most
commonly in patients with grade three and four
HO.Surgery should be delayed until the HO is
mature. Attempts to remove the bone prior to
maturity have an increased rate of recurrence.
After the bone is excised, the patient should
receive prophylaxis to prevent recurrence with
either indomethacin or radiation therapy.
Radiation therapy is preferred in most patients as
it is usually a one-dose regimen of 700–800cGy
and can be administered either immediately preoperatively or within the rst 2 or 3days postoperatively. The rate of recurrence after excision
and prophylaxis is approximately 5–20%.
The limitations to the long-term xation of a
total hip arthroplasty are loosening and wear. As
the implant, particularly the polyethylene liner,
wears, the debris that is produced is released into
the local tissues. The body has no mechanism to
digest or eliminate the polyethylene debris.
However, the local macrophages in the area recognize the material as a foreign substance and try
to eliminate the debris. The macrophages ingest
the material and try to digest it with catabolic
enzymes and super-oxides, which fails to alter
the material. As the debris accumulates within
the cell, it breaks down, releasing the polyethylene, enzymes, and oxides into the local environment. This results in a local bone lysis that creates
cysts in the bone and dissects along the xation
of the implant or cement and bone. If allowed to
continue, the lysis leads to loosening.
Loosening can also result from mechanical
failure of the implant bone or cement interface.
The cement mantle can fragment or fracture,
leaving the implant loose. In non-cemented xation, the implant can also loosen. This can occur
due to failed bony ingrowth resulting in a brous
xation. This brous tissue may not be sufcient
to maintain stable xation of the implant. The
implant will then migrate slowly, best appreciated on serial radiographs. This will require revision to provide a stable implant.
Similar to the indications for primary arthroplasty, these are elective surgeries. However, in
the revision setting, it is important to follow the
patient closely with plain radiographs. If an
accelerated pattern of bone loss is noted, revision
surgery should be performed prior to the loss of
an extensive amount of bone. The greater the loss
of bone at the time of revision, the greater the difculty in obtaining stable xation for the revision
components. This may also lead to a higher rate
of repeated revision for aseptic loosening.
Summary
As noted initially, disorders involving the hip and
femur are manifested by alteration in a patient’s
ability to ambulate. These can be diagnosed and
treated by obtaining a careful history, thorough
physical examination, and the appropriate use of
radiographic studies. When proper diagnosis is
made for most non-traumatic disorders, it is usually best to begin with non-operative treatment
options. If the non-operative treatment alternatives are not successful, then operative intervention is considered and can result in an excellent
outcome in the majority of patients.
Further Reading
Bauer TW, Parvizi J, Kobayashi N, Krebs V. Diagnosis
of periprosthetic infection. J Bone Joint Surg Am.
2006;88:869–82.
Brooker AF, Bowerman JW, Robinson RA, Riley LH Jr.
Ectopic ossication following total hip replacement.
Incidence and a method of classication. J Bone Joint
Surg Am. 1973;55(8):1629–32.
Byrd JW. Hip arthroscopy. J Am Acad Orthop Surg.
2006;14(7):433–44.
Callaghan JJ, Templeton JE, Liu SS, et al. Results of
Charnley total hip arthroplasty at a minimum of 30
years. A concise follow-up of a previous report. J Bone
Joint Surg Am. 2004;86-A(4):690–5.
Collier JP, Sutula LC, Currier BH, et al. Overview of
polyethylene as a bearing material: comparison
of sterilization methods. Clin Orthop Relat Res.
1996;333:76–86.
13 Hip Osteoarthritis andArthroplasty
349
Evans BG.Late complications and their management. In:
Callaghan JJ, Rosenberg AG, Rubash HE, editors. The
adult hip. New York, NY: Lippincott-Raven; 1998.
p.1149–61.
Garvin KL, Evans BG, Salvati EA, Brause BD.Palacos
gentamicin for the treatment of deep periprosthetic hip
infections. Clin Orthop Relat Res. 1994;298:97–105.
Healy WL, Lo TC, DeSimone AA, Rask B, Pfeifer
BA. Single-dose irradiation for the prevention of
heterotopic ossication after total hip arthroplasty.
A comparison of doses of ve hundred and fty and
seven hundred centigray. J Bone Joint Surg Am.
1995;77(4):590–5.
Hoaglund FT, Steinbach LS.Primary osteoarthritis of the
hip: etiology and epidemiology. J Am Acad Orthop
Surg. 2001;9(5):320–7.
Jazrawi LM, Kummer FJ, DiCesare PE.Alternative bear-
ing surfaces for total joint arthroplasty. J Am Acad
Orthop Surg. 1998;6(4):198–203.
Meehan J, Jamali AA, Nguygen H.Prophylactic antibiot-
ics in hip and knee arthroplasty. J Bone Joint Surg Am.
2009;91(10):2480–90.
Steinberg ME.Early diagnosis, evaluation, and staging
of osteonecrosis. Instr Course Lect. 1994;43:513–8.
Trousdale RT, Ekkernkamp A, Ganz R, Wallrichs
SL. Periacetabular and intertrochanteric osteotomy
for the treatment of osteoarthrosis in dysplastic hips.
J Bone Joint Surg Am. 1995;77(1):73–85.
Wiklund I, Romanus B.A comparison of quality of life
before and after arthroplasty in patients who had
arthrosis of the hip joint. J Bone Joint Surg Am.
1991;73(5):765–9.
Willert HG, Bertram H, Buchhorn GH.Osteolysis in allo-
arthroplasty of the hip. The role of ultra-high molecu-
lar weight polyethylene wear particles. Clin Orthop
Relat Res. 1990;258:95–107.
Woo RYG, Morrey BF.Dislocations after total hip arthro-
plasty. J Bone Joint Surg Am. 1982;64(9):1295–306.
Fernandez MA, Achten J, Parsons N, Grifn XL, Png
ME, Gould J, McGibbon A, Costa ML, WHiTE 5
Investigators. Cemented or uncemented hemiarthro-
plasty for intracapsular hip fracture. N Engl J Med.
2022;386(6):521–30.
Parilla FW, Youngman TR, Layon DR, Ince DC, Pashos
GE, Maloney WJ, Clohisy JC.Excellent 20-year results
of Total hip arthroplasty with highly cross-linked
polyethylene on cobalt-chromium femoral heads in
patients ≤50 years. J Arthroplast. 2024;39(2):409–15.
Knee Osteoarthritis
andArthroplasty
EvanJacquez, BrianG.Evans, andKennethM.Vaz
14
Introduction
This chapter will discuss the anatomy, biomechanics, and pathology of the knee as well as the
pathophysiology and treatment of one of its most
common ailments: osteoarthritis. The function of
the knee is provided primarily by the soft tissue.
Therefore, injury to these soft tissue structures
will have a signicant impact upon the stability
of the knee.
Anatomy
The osseous anatomy of the knee consists of the
proximal tibia, the distal femur, and the patella
(Fig. 14.1). The distal femur consists of the
medial and lateral condyles, the medial and lateral epicondyles, femoral trochlear groove, and
the intercondylar notch. The medial condyle is
larger and extends slightly distal compared to the
lateral condyle. Both condyles are covered with
articular cartilage. The trochlear groove lies on
the anterior aspect of the distal femur between
E. Jacquez (*) · B. G. Evans · K. M. Vaz
MedStar Georgetown Orthopedic Institute,
Georgetown University School of Medicine,
Washington, DC, USA
Department of Orthopedics, MedStar Georgetown
University Hospital, Washington, DC, USA
e-mail: Evan.A.Jacquez@medstar.net;
Kenneth.M.Vaz@medstar.net
the medial and lateral femoral condyles. This surface is also covered by the articular cartilage and
serves as the site of articulation of the patella.
The lateral rim of the trochlear groove is frequently more prominent than the medial side to
allow for proper patellar tracking along the femur.
The epicondyles serve as the site of insertion
of several important structures. The deep and
supercial medial collateral ligaments (MCL)
attach to the medial epicondyle. The proximal
margin of the medial epicondyle is enlarged and
serves as the site of insertion of the adductor
magnus (the adductor tubercle). The lateral or
bular collateral ligament (LCL) attaches to the
lateral epicondyle. Inferior to the attachment of
the LCL is the insertion of the popliteus muscle
at the junction of the lateral condyle and epicondyle. The medial and lateral heads of the gastrocnemius muscle originate from the medial and
lateral posterior femoral condyles. The intercondylar notch is the site of the femoral attachment
of the cruciate ligaments. The anterior cruciate
ligament (ACL) attaches in the posterior lateral
aspect of the notch and the posterior cruciate ligament (PCL) attaches in the anterior medial
aspect of the notch.
The proximal tibial surface is composed of the
medial and lateral plateaus and the intercondylar
eminence. The medial plateau is larger and
extends further posterior compared to the lateral
plateau. The surface of the medial plateau is
slightly concave, whereas the lateral tibial pla-
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024
W. F. Postma et al. (eds.), Essentials of Orthopedic Surgery,
https://doi.org/10.1007/978-3-031-66215-7_14
351
352
Femoral (trochlear)
groove
Lateral condyle
Medial condyle
E. Jacquez et al.
Grant's notch
Intercondylar
notch
Tibial spines
Tibial plateaus
Fig. 14.1 Bony anatomy and major ligamentous structures of the exed knee joint (anterior view)
teau is in fact slightly convex. Both of the tibial
plateaus are covered with articular cartilage. The
intercondylar eminence is the site of attachment
of the menisci and the cruciate ligaments.
don of the quadriceps mechanism. There are two
major facets on the patella, the medial and lateral
facets. There is signicant variability in the size
and orientation of these facets. However, normally
the lateral facet is broader and the medial facet is
more acutely oriented to the femoral trochlea.
little to the stability of the knee. Stability and
function are therefore provided by the complex
soft tissue envelope around and in the knee
(Figs.14.2 and 14.3). The soft tissue components
of the knee can be divided into several components: static restraints (ligaments), dynamic
restraints (muscles and tendons), and the menisci.
The static restraints are represented by the medial
collateral ligament (MCL), lateral collateral ligament (LCL), anterior cruciate ligament (ACL),
and posterior cruciate ligament (PCL). These
structures resist valgus and varus stress as well as
anterior and posterior translation of the tibia relative to the femur. The MCL consists of two layers.
Lateral
collateral
ligament
Lateral
meniscus
The patella is a sesamoid bone within the ten-
The osseous anatomy of the knee provides
Posterior cruciate
ligament
Deep medial
collateral ligament
Anterior cruciate
ligament
Medial meniscus
Coronary ligament
Patellar tendon
The deep MCL spans from the medial epicondyle
of the femur to the proximal tibial border, just
below the medial tibial plateau. The supercial
MCL has the same femoral origin; however, the
ligament has a broad tibial insertion extending
6–10cm below the tibial plateau along the posterior medial border of the tibia. The LCL is a more
discrete band along the lateral aspect of the knee.
It spans from its origin on the lateral femoral epicondyle and inserting not on the proximal tibia
but instead on the bular head.
The ACL resists the anterior translation of the
tibia relative to the femur. The ligament runs
from the anterior aspect of the tibial eminence to
the posterior lateral aspect of the femoral notch.
The PCL resists posterior translation of the tibia
relative to the femur and resists hyperextension
of the knee. The ligament extends from the posterior aspect of the intercondylar eminence and
proximal tibia in the midline to the anterior
medial aspect of the femoral intercondylar notch.
The dynamic restraints in the knee are the
muscles and tendons which cross the knee joint.
These are broadly divided into muscles which act
to extend and those which act to ex the knee.
The extensor muscles are the quadriceps femoris
Ligament of Wrisberg
Lat
lig
Transverse ligament
Posterior cruciate
Co
(meniscotibial lig
14 Knee Osteoarthritis andArthroplasty
353
Fig. 14.2 Cross section
of the knee
demonstrating the
menisci and associated
ligaments
Fig. 14.3 Posterior
aspect of the knee joint
eral collateral
ament
Popliteal
tendon
Popliteal
hiatus
(recess)
Coronary
ligament
(meniscotibial)
Lateral meniscus
Posterior cruciate
ligament
Medial meniscus
ronary ligament
Superficial medial
collateral ligament
Ligament of Humphry
ament)
ligament
Anterior cruciate
ligament
Anterior
meniscofemoral ligament
(ligament of Humphry)
Capsule
Deep medial
collateral
ligament
Superficial
medial
collateral
ligament
Medial meniscus
Anterior cruciate
ligament
Posterior
meniscofemoral ligament
(ligament of Wrisberg)
Lateral meniscus
Popliteus tendon
(under arcuate ligament)
Arcuate ligament
Lateral collateral
ligament
Popliteus muscle
Soleal line
and the tensor fascia lata. The quadriceps is a
group of four muscles all inserting onto the
patella and patellar tendon, which in turn inserts
upon the anterior tibial tubercle. The muscles that
make up the quadriceps are the rectus femoris,
vastus lateralis, vastus medialis, and vastus intermedius. These are all innervated by the femoral
nerve. The tensor fascia lata originates upon the
pelvic brim and inserts at Gerdy’s tubercle on the
proximal anterolateral tibia. The tensor fascia
lata is innervated by the superior gluteal nerve.
The primary exors of the knee are the hamstring muscles—semimembranosus, semitendinosus, and the biceps femoris—and the sartorius
and gracilis. The hamstring muscles originate
on the ischium and insert on the posterior
medial and lateral proximal tibia. They receive
their innervation from the sciatic nerve; all are
innervated by the tibial division of the sciatic
nerve except the short head of the biceps which
is innervated by the peroneal division of the sciatic nerve. The sartorius originates from the
354
E. Jacquez et al.
anterior superior iliac spine and the gracilis
originates from the pubis. Both of these muscles with the semitendinosus insert into the
proximal medial tibia in the pes anserine
(goose’s foot, relating to the appearance of the
three tendons inserting together). The sartorius
is innervated by the femoral nerve and the gracilis by the obturator nerve.
The other muscles that serve to ex the knee
are the gastrocnemius and popliteus which extend
from the posterior aspect of the femoral condyles
to the calcaneus and proximal tibia, respectively.
The menisci are two crescent-shaped brocartilaginous structures attached to the proximal
tibial surface. They increase the surface area for
weight-bearing, therefore, reducing the peak
stress exerted upon the articular cartilage while
also providing shock absorption. Additionally,
they provide a small degree of stability to the
knee by changing the relatively at tibial articular surface to a cupped surface. The menisci are
composed of dense organized cartilage tissue.
Biomechanics oftheKnee
The mechanical axis of the lower extremity
extends from the center of rotation of the hip to
the center of the ankle joint. This normally
crosses the knee joint in the lateral third of the
medial tibial plateau. The normal anatomic
alignment of the knee is 5–7° of valgus. When
the knee is loaded, the medial compartment
receives 60% of the weight-bearing stress and
the lateral compartment receives 40% of the
weight-bearing stress. This difference in the
applied load in the normal knee is why the
medial tibial plateau and medial femoral condyle
are larger than the lateral side. Patients with signicant angular deformity of the knee will have
altered weight-bearing, resulting in increased
stress in the medial (with varus or bow-legged
deformity) or lateral (with valgus or knock-knee
deformity) compartment. The increased stress
will frequently result in early arthritis in the
overused compartment of the knee.
The highest joint forces, however, are found in
the patellofemoral articulation. Forces as high as
three to ve times the body weight across the
patellofemoral articulation can be noted for activities such as stair climbing and jumping. The
function of the patella is to provide a mechanical
advantage to the quadriceps tendon. The patella
moves the line of pull of the quadriceps further
away from the center of rotation, thereby acting
as a lever and reducing the force required to
extend the knee. Patients who have had the patella
removed as a result of arthritis or trauma are
noted to have an approximately 30% reduction in
the force in the quadriceps compared to patients
with a patella.
Evaluation ofthePainful Knee
History
The history should begin with the chief complaint and how long the patient has experienced
the problem: the specic location of pain, any
radiation, the nature of the pain (ache, burning,
stabbing, etc.), and any exacerbating or ameliorating factors. The relationship of the pain with
activity and rest is important to note in particular. Pain in the musculoskeletal system will commonly be relieved with rest. Severe pain that is
present at rest can signal a septic process or
neoplasm.
Frequently, knee problems begin with an
injury. Detailed history describing the injury can
be very helpful in determining the structures that
are injured. The nature of any external force contacting the knee and the position of the knee at
the time of injury should be elicited. Did an audible or palpable pop occur at the time of the
injury? Shifting or abnormal movement of the
knee may also have been noted at the time of
injury. The degree and nature of any swelling
around the knee are important to record. In addition to the description of injury, it is helpful to
inquire about the patient’s ability to use the knee
after the injury: was the patient able to weight
bear, was the onset of pain or swelling immediate
or delayed, and could the patient ex or extend
the knee after injury are important questions to
ask the patient after knee injury.
14 Knee Osteoarthritis andArthroplasty
355
In addition to pain, patients with knee problems will complain of mechanical problems in
the knee. Patients may note an inability to fully
bend or straighten the knee. This is referred to as
locking of the knee. Locking can be a result of a
loose body in the knee becoming lodged between
the femoral condyle and tibial plateau, similar to
a wedge “door stop.” The patients who note intermittent locking of the knee will usually be able to
relieve the locked knee by gently moving the
knee without weight-bearing. This maneuver
allows the loose fragment to be released from
between the femur and tibia and motion will be
restored. However, inability to fully ex and
extend the knee can also be noted in patients with
large effusions and ligament injuries.
Instability is another frequent complaint of
patients with knee injuries. Patients will observe
that their knee will shift or buckle with particular
activities. Instability can result from two general
etiologies. The rst is ligamentous injuries. As
noted previously, the stability of the knee is a
result of the ligaments which cross from the tibia
to the femur. Disruption of the ligaments will
result in alteration of knee function; the knee may
shift or subluxate with activity. The second common cause of a knee buckling or giving way is
problems in the patellofemoral joint. Instability
of the patella in the trochlear groove will result in
a giving way sensation as the patella subluxates.
Damage to the articular surfaces of the patella or
the trochlear groove will result in pain as the
patella tracks over the trochlea. This can occasionally lead to a sharp acute pain which will lead
to the quadriceps releasing its contraction while
the patient is weight-bearing on the leg as a result
of a primitive reex arc. The patient will note a
giving way or buckling sensation in the knee and
a few patients may actually fall as a result.
The majority of knee complaints are aggravated by activities. The specic problems the
patient has encountered are important to note.
Patients will commonly have difculty ascending
and descending stairs. Frequently descending
stairs will be the most symptomatic as this places
high stress across the patellofemoral joint.
Bicycling can also aggravate the patellofemoral
joint. Activities that involve quadriceps contrac-
tion with the knee in exion may result in subluxation in patients with patellar instability. Patients
with meniscal tears will have difculty squatting
and may notice snapping or pain when rising
from a chair or ascending stairs. Activities that
involve stopping and turning or cutting will result
in the knee shifting or giving way if there is insufciency in the collateral or cruciate ligaments.
Physical Examination
Physical examination of the patient with a knee
complaint begins with inspection. Observation of
the alignment of the lower extremity should demonstrate a normal 5–7° valgus angle at the knee
when a patient is standing. Deformity of the leg
in varus or valgus beyond the normal 5–7° can be
associated with either a ligamentous or osseous
deciency. Any swelling, bruising, or ecchymosis should be recorded. Next, the evaluation
should focus on the patient’s gait. Normal gait
requires the range of motion from 0 to 65° of
exion. The gait should have a smooth cadence
with the length of each step being equal on the
left and right sides. The knee should not demonstrate any sudden shift to either the lateral or
medial side. If abnormal lateral motion is noted,
this is recorded as a medial or lateral thrust,
respectively.
The knee should then be examined with the
patient sitting with their legs over the edge of the
examining table. The position of the patella
should be anterior and symmetric. The patellar
tracking can then be followed by asking the
patient to ex and extend the knee with the examiner palpating the patella. There should be little
lateral movement. Crepitus may also be noted as
a grinding sensation between the patella and the
femoral trochlear groove.
The knee should then be examined with the
patient supine. For all aspects of the examination,
the contralateral knee can be used as a normal control. Effusion or uid within the knee can be
assessed by placing both hands on the knee with
one below the patella and one above the patella.
Any uid in the knee can then be displaced and
palpated proximally and distally. The knee can be