Chapter 18

Chapter 18Chapter 18

The Knee ComplexThe Knee Complex

OverviewOverview

The knee joint complex is extremely The knee joint complex is extremely elaborate and includes three articulating elaborate and includes three articulating surfaces, which form two distinct joints surfaces, which form two distinct joints contained within a single joint capsule: contained within a single joint capsule: the patellofemoral and tibiofemoral jointthe patellofemoral and tibiofemoral joint

Given the frequency of knee injuries and Given the frequency of knee injuries and the intricate nature of this joint complex, the intricate nature of this joint complex, clinicians caring for knee injuries must clinicians caring for knee injuries must have an extensive knowledge basehave an extensive knowledge base

AnatomyAnatomy

The tibiofemoral joint The tibiofemoral joint – The tibiofemoral joint consists of the The tibiofemoral joint consists of the

distal end of the femur and the distal end of the femur and the proximal end of the tibiaproximal end of the tibia

– The The distal aspect of the femur is distal aspect of the femur is composed of two femoral condyles that composed of two femoral condyles that are separated by an intercondylar are separated by an intercondylar notchnotch

The intercondylar notch serves to accept The intercondylar notch serves to accept the anterior cruciate ligament (ACL) and the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL)the posterior cruciate ligament (PCL)

AnatomyAnatomy

Distal femurDistal femur– The femoral condyles project posteriorly from The femoral condyles project posteriorly from

the femoral shaftthe femoral shaft– The smaller lateral femoral condyle is ball-The smaller lateral femoral condyle is ball-

shaped and faces outward, while the elliptical-shaped and faces outward, while the elliptical-shaped medial femoral condyle faces inward shaped medial femoral condyle faces inward

– The lateral epicondyle serves as the origin for The lateral epicondyle serves as the origin for the lateral head of the gastrocnemius, and the the lateral head of the gastrocnemius, and the lateral collateral ligament (LCL)lateral collateral ligament (LCL)

– The medial condyle serves as the insertion The medial condyle serves as the insertion site for the adductor magnus, and the medial site for the adductor magnus, and the medial collateral ligament (MCL)collateral ligament (MCL)

AnatomyAnatomy

Femoral condylesFemoral condyles– The anterior-posterior length of the The anterior-posterior length of the

medial femoral condyle is greater medial femoral condyle is greater than its lateral counterpart by about than its lateral counterpart by about 1.7 cm1.7 cm

– The length of the articular surface of The length of the articular surface of the medial femoral condyle is longer the medial femoral condyle is longer than the length of the lateral than the length of the lateral femoral condylefemoral condyle

AnatomyAnatomy

Proximal tibiaProximal tibia– The proximal tibia is composed of two plateaus The proximal tibia is composed of two plateaus

separated by the intercondylar eminence, separated by the intercondylar eminence, including the medial and lateral tibial spines including the medial and lateral tibial spines

– The tibial plateaus are concave in a medial-lateral The tibial plateaus are concave in a medial-lateral directiondirection

– In the anterior-posterior direction, the medial In the anterior-posterior direction, the medial tibial plateau is also concave, while the lateral is tibial plateau is also concave, while the lateral is convex, producing more asymmetry, and an convex, producing more asymmetry, and an increase in lateral mobilityincrease in lateral mobility

– The medial plateau has an approximately 50% The medial plateau has an approximately 50% greater surface area than the lateral plateau, and greater surface area than the lateral plateau, and its articular surface is 3 times thickerits articular surface is 3 times thicker

AnatomyAnatomy

Patellofemoral JointPatellofemoral Joint– The patellofemoral joint is a complex The patellofemoral joint is a complex

articulation, dependent on both dynamic and articulation, dependent on both dynamic and static restraints for its function and stabilitystatic restraints for its function and stability

– The patella is a very hard triangular-shaped The patella is a very hard triangular-shaped bone, situated in the intercondylar notch, and bone, situated in the intercondylar notch, and embedded in the tendon of the quadriceps embedded in the tendon of the quadriceps femoris muscle above, and the patella femoris muscle above, and the patella tendon belowtendon below

– The posterior surface of the patella can The posterior surface of the patella can include up to seven facets, with three on the include up to seven facets, with three on the medial and lateral surfaces medial and lateral surfaces

AnatomyAnatomy

The patellofemoral joint functions to:The patellofemoral joint functions to:– Provide an articulation with low frictionProvide an articulation with low friction– Protect the distal aspect of the femur from Protect the distal aspect of the femur from

trauma, and the quadriceps from attritional trauma, and the quadriceps from attritional wearwear

– Improve the cosmetic appearance of the kneeImprove the cosmetic appearance of the knee– Improve the moment arm of the quadriceps Improve the moment arm of the quadriceps – Decrease the amount of anterior-posterior Decrease the amount of anterior-posterior

tibiofemoral shear stress placed on the knee tibiofemoral shear stress placed on the knee joint joint

AnatomyAnatomy

The knee joint capsuleThe knee joint capsule– is composed of a thin, strong fibrous is composed of a thin, strong fibrous

membranemembrane– is the largest synovial capsule in the bodyis the largest synovial capsule in the body– A synovial membrane lines the inner A synovial membrane lines the inner

portion of the knee joint capsule. By lining portion of the knee joint capsule. By lining the joint capsule, the synovial membrane the joint capsule, the synovial membrane excludes the cruciate ligaments from the excludes the cruciate ligaments from the interior portion of the knee joint, making interior portion of the knee joint, making them extrasynovial yet intra-articularthem extrasynovial yet intra-articular

AnatomyAnatomy

The proximal tibiofibular joint The proximal tibiofibular joint – An almost plane joint with a slight An almost plane joint with a slight

convexity on the oval tibial facet and convexity on the oval tibial facet and a slight concavity of the fibular heada slight concavity of the fibular head

– Has more motion than its distal Has more motion than its distal partner partner

AnatomyAnatomy

LigamentsLigaments– The static stability of the knee joint The static stability of the knee joint

complex depends on four major complex depends on four major knee ligaments, which provide a knee ligaments, which provide a primary restraint to abnormal knee primary restraint to abnormal knee motionmotion Anterior cruciateAnterior cruciate Posterior cruciatePosterior cruciate Medial collateralMedial collateral Lateral collateralLateral collateral

AnatomyAnatomy

The cruciate ligamentsThe cruciate ligaments– Are intra-articular/extra synovial Are intra-articular/extra synovial

because of the posterior because of the posterior invagination of the synovial invagination of the synovial membranemembrane

– Are different from those of other Are different from those of other joints, in that, they restrict normal joints, in that, they restrict normal motion, rather than restrict motion, rather than restrict abnormal motionabnormal motion

AnatomyAnatomy

Both the anterior cruciate Both the anterior cruciate ligament (ACL) and the posterior ligament (ACL) and the posterior cruciate ligament (PCL) are each cruciate ligament (PCL) are each named according to their named according to their attachment sites on the tibiaattachment sites on the tibia

AnatomyAnatomy

The anterior cruciate ligamentThe anterior cruciate ligament– One of the most important ligaments One of the most important ligaments

to knee stabilityto knee stability– Serves as a primary restraint to Serves as a primary restraint to

anterior translation of the tibia anterior translation of the tibia relative to the femur, and a relative to the femur, and a secondary restraint to both internal secondary restraint to both internal and external rotation in the non-and external rotation in the non-weight bearing knee weight bearing knee

AnatomyAnatomy

The posterior cruciate ligamentThe posterior cruciate ligament– Provides 90-95% of the total Provides 90-95% of the total

restraint to posterior translation of restraint to posterior translation of the tibia on the femur, with the the tibia on the femur, with the remainder being provided by the remainder being provided by the collateral ligaments, posterior collateral ligaments, posterior portion of the medial and lateral portion of the medial and lateral capsules, and the popliteus tendoncapsules, and the popliteus tendon

AnatomyAnatomy

The medial collateral ligament The medial collateral ligament (MCL)(MCL)– The anterior fibers of this ligament The anterior fibers of this ligament

are taut in flexion, and can be are taut in flexion, and can be palpated easily in this positionpalpated easily in this position

– The posterior fibers, which are taut The posterior fibers, which are taut in extension, blend intimately with in extension, blend intimately with the capsule and with the medial the capsule and with the medial border of the medial meniscus, border of the medial meniscus, making them difficult to palpatemaking them difficult to palpate

AnatomyAnatomy

The lateral collateral ligament The lateral collateral ligament (LCL) (LCL) – The main function of the LCL is to The main function of the LCL is to

resist varus forcesresist varus forces It offers the majority of the varus It offers the majority of the varus

restraint at 25° of knee flexion, and in restraint at 25° of knee flexion, and in full extension full extension

AnatomyAnatomy

Secondary restraints include:Secondary restraints include:– The structures in the posterior-The structures in the posterior-

lateral and posterior-medial corners lateral and posterior-medial corners of the kneeof the knee

– The hamstrings and quadricepsThe hamstrings and quadriceps– The patellar ligament, oblique The patellar ligament, oblique

popliteal ligaments, and the fabella popliteal ligaments, and the fabella

AnatomyAnatomy

MenisciMenisci– The crescent-shaped lateral and The crescent-shaped lateral and

medial menisci, attached on top of medial menisci, attached on top of the tibial plateaus, are pieces of the tibial plateaus, are pieces of fibrocartilage material that lie fibrocartilage material that lie between the articular cartilage of between the articular cartilage of the femur and the tibia the femur and the tibia

AnatomyAnatomy

Medial meniscusMedial meniscus– Semi-lunar or C-shapedSemi-lunar or C-shaped– Larger and thicker than its lateral Larger and thicker than its lateral

counterpartcounterpart– Sits in the concave medial tibial Sits in the concave medial tibial

plateauplateau– Wider posteriorly than anteriorly Wider posteriorly than anteriorly

AnatomyAnatomy

Lateral meniscusLateral meniscus– Rounder O-shapedRounder O-shaped– Sits atop the convex lateral tibial plateauSits atop the convex lateral tibial plateau– Smaller and thinner, than its medial Smaller and thinner, than its medial

counterpartcounterpart– More mobile than its medial counterpartMore mobile than its medial counterpart– Two mensicofemoral ligaments, the Two mensicofemoral ligaments, the

ligaments of Humphrey and Wrisberg ligaments of Humphrey and Wrisberg attach to the lateral meniscus attach to the lateral meniscus

AnatomyAnatomy

Menisci FunctionMenisci Function– The menisci assist in a number of The menisci assist in a number of

functions including load functions including load transmission, shock absorption, joint transmission, shock absorption, joint lubrication, joint stability and the lubrication, joint stability and the guiding of movementsguiding of movements

AnatomyAnatomy

BursaeBursae– There are a number of bursae There are a number of bursae

situated in the soft tissues around situated in the soft tissues around the knee joint the knee joint

– The bursae serve to reduce friction, The bursae serve to reduce friction, and to cushion the movement of one and to cushion the movement of one body part over anotherbody part over another

AnatomyAnatomy

PlicaPlica– Synovial plica represents a remnant Synovial plica represents a remnant

of the three separate cavities in the of the three separate cavities in the synovial mesenchyme of the synovial mesenchyme of the developing kneedeveloping knee

AnatomyAnatomy

RetinaculaRetinacula– Formed from structures in the first Formed from structures in the first

and second layers of the knee jointand second layers of the knee joint– The retinacula can be subdivided The retinacula can be subdivided

into the medial and the lateral into the medial and the lateral retinacula for clinical examination retinacula for clinical examination and intervention purposesand intervention purposes

AnatomyAnatomy

MusclesMuscles– The major muscles that act on the The major muscles that act on the

knee joint complex are the knee joint complex are the quadriceps, the hamstrings quadriceps, the hamstrings (semimembranosus, (semimembranosus, semitendinosus, and the biceps semitendinosus, and the biceps femoris), the gastrocnemius, the femoris), the gastrocnemius, the popliteus, and the hip adductors popliteus, and the hip adductors

AnatomyAnatomy

Vascular supplyVascular supply– The major blood supply to this area The major blood supply to this area

comes from the femoral, popliteal, comes from the femoral, popliteal, and genicular arteriesand genicular arteries

AnatomyAnatomy

NeurologyNeurology– Femoral nerveFemoral nerve

Saphenous nerveSaphenous nerve

– Sciatic nerveSciatic nerve Common peronealCommon peroneal TibialTibial

BiomechanicsBiomechanics

The tibiofemoral joint The tibiofemoral joint – The tibiofemoral joint, or knee joint, is a The tibiofemoral joint, or knee joint, is a

ginglymoid, or modified hinge joint, which ginglymoid, or modified hinge joint, which has six degrees of freedomhas six degrees of freedom

– The bony configuration of the knee joint The bony configuration of the knee joint complex is geometrically incongruous and complex is geometrically incongruous and lends little inherent stability to the jointlends little inherent stability to the joint

– Joint stability is therefore dependent upon Joint stability is therefore dependent upon the static restraints of the joint capsule, the static restraints of the joint capsule, ligaments, and menisci, and the dynamic ligaments, and menisci, and the dynamic restraints of the quadriceps, hamstrings, restraints of the quadriceps, hamstrings, and gastrocnemiusand gastrocnemius


Patellofemoral jointPatellofemoral joint – To assist in the control of the forces To assist in the control of the forces

around the patellofemoral joint, around the patellofemoral joint, there are a number of static and there are a number of static and dynamic restraintsdynamic restraints


The Quadriceps (‘Q’) angleThe Quadriceps (‘Q’) angle– Can be described as the angle formed by Can be described as the angle formed by

the bisection of two lines, one line drawn the bisection of two lines, one line drawn from the anterior superior iliac spine (ASIS) from the anterior superior iliac spine (ASIS) to the center of the patella, and the other to the center of the patella, and the other line drawn from the center of the patella to line drawn from the center of the patella to the tibial tubercle the tibial tubercle

– The most common ranges cited are 8-14° The most common ranges cited are 8-14° for males and 15-17° for femalesfor males and 15-17° for females

– Angles of greater than 20° are considered Angles of greater than 20° are considered abnormal and may be indicative of potential abnormal and may be indicative of potential displacement of the patelladisplacement of the patella


Patella-Femur Contact and Patella-Femur Contact and LoadingLoading– The amount of contact between the The amount of contact between the

patella and the femur appears to patella and the femur appears to vary according to a number of vary according to a number of factors including:factors including: The angle of knee flexionThe angle of knee flexion The location of contactThe location of contact The surface area of contactThe surface area of contact The patellofemoral joint reaction forceThe patellofemoral joint reaction force


Patella StabilityPatella Stability– Patella stability is dependent on 2 Patella stability is dependent on 2

factors:factors: Static restraintsStatic restraints Dynamic restraintsDynamic restraints


Patellar TrackingPatellar Tracking– In the normal knee, the patella glides in a In the normal knee, the patella glides in a

sinuous path inferiorly and superiorly during sinuous path inferiorly and superiorly during flexion and extension respectively, covering flexion and extension respectively, covering a distance of 5-7 cm with respect to the a distance of 5-7 cm with respect to the femurfemur

– One proposed mechanism for abnormal One proposed mechanism for abnormal patellar tracking is an imbalance in the patellar tracking is an imbalance in the activity of the of the vastus medialis activity of the of the vastus medialis obliquus (VMO) relative to the vastus obliquus (VMO) relative to the vastus lateralis (VLlateralis (VL))


Open and Closed Kinetic Chain ActivitiesOpen and Closed Kinetic Chain Activities – An understanding of the forces generated and An understanding of the forces generated and

the muscle activity employed by different the muscle activity employed by different exercises is essential for determining how to exercises is essential for determining how to achieve optimal balance of muscle force, achieve optimal balance of muscle force, ligament tension, and joint compressionligament tension, and joint compression

– Whether the motion occurring at the knee joint Whether the motion occurring at the knee joint complex occurs as a closed or open kinetic complex occurs as a closed or open kinetic chain has implications on the biomechanics chain has implications on the biomechanics and the joint compressive forces induced and the joint compressive forces induced

ExaminationExamination

HistoryHistory– The diagnosis of tibiofemoral and The diagnosis of tibiofemoral and

patellofemoral joint disorders can patellofemoral joint disorders can often be made on the history and often be made on the history and physical examination alonephysical examination alone With the larger number of specific tests With the larger number of specific tests

available for the knee joint complex, it available for the knee joint complex, it is tempting to overlook the important is tempting to overlook the important role of the history, which can detail both role of the history, which can detail both the chronology, and mechanism, of the chronology, and mechanism, of eventsevents


HistoryHistory– The mechanism of the injury is one of the The mechanism of the injury is one of the

most important aids in making a diagnosismost important aids in making a diagnosis– The position of the joint at the time of the The position of the joint at the time of the

traumatic force dictates which anatomic traumatic force dictates which anatomic structures are at risk for injurystructures are at risk for injury

– The primary mechanisms of injury in the The primary mechanisms of injury in the knee are direct trauma, a varus or valgus knee are direct trauma, a varus or valgus force (with or without rotation), force (with or without rotation), hyperextension, flexion with posterior hyperextension, flexion with posterior translation, a twisting force, and overuse translation, a twisting force, and overuse


HistoryHistory– There is a significant temptation to cut There is a significant temptation to cut

corners with a patient who presents with corners with a patient who presents with anterior knee pain, and to proceed directly anterior knee pain, and to proceed directly to the diagnosis of patellofemoral painto the diagnosis of patellofemoral pain

– Particular activities can help with Particular activities can help with differential diagnosisdifferential diagnosis

Complaints of pain that occur when a patient Complaints of pain that occur when a patient arises from a seated position, negotiates stairs, arises from a seated position, negotiates stairs, or squats, are associated with patellofemoral or squats, are associated with patellofemoral dysfunction dysfunction


Systems ReviewSystems Review– Knee pain can be referred to the Knee pain can be referred to the

knee from the lumbosacral region (L knee from the lumbosacral region (L 3 to S 2 segments), or from the hip3 to S 2 segments), or from the hip


ObservationObservation– The observation component of the The observation component of the

examination begins as the clinician examination begins as the clinician meets the patient and ends as the meets the patient and ends as the patient is leavingpatient is leaving

– This informal observation should This informal observation should occur at every visitoccur at every visit


Active Range of Motion with Passive Over Active Range of Motion with Passive Over pressurepressure– Normal knee motion has been described as 0° Normal knee motion has been described as 0°

of extension to 135° of flexion, although of extension to 135° of flexion, although hyperextension is frequently present to varying hyperextension is frequently present to varying degreesdegrees

– Passive movements, as elsewhere, can Passive movements, as elsewhere, can determine the amount of motion and the end-determine the amount of motion and the end-feelfeel

– Resisted testing is performed to provide the Resisted testing is performed to provide the clinician with information about the integrity of clinician with information about the integrity of the neuromuscular unit, and to highlight the the neuromuscular unit, and to highlight the presence of muscle strainspresence of muscle strains


PalpationPalpation– For palpation to be reliable, the For palpation to be reliable, the

clinician must have a sound clinician must have a sound knowledge of surface anatomy, and knowledge of surface anatomy, and the results from the palpation exam the results from the palpation exam should be correlated with other should be correlated with other findingsfindings


Functional TestsFunctional Tests– Functional outcome following knee Functional outcome following knee

injury must consider the patient’s injury must consider the patient’s perspective, and not just objective perspective, and not just objective measurements of instabilitymeasurements of instability

– Functional motion requirements of the Functional motion requirements of the knee vary according to the specific taskknee vary according to the specific task

– A number of commonly used rating A number of commonly used rating scales can be used to assess knee scales can be used to assess knee functionfunction


Special TestsSpecial Tests– Special tests are merely confirmatory Special tests are merely confirmatory

tests and should not be used alone to tests and should not be used alone to form a diagnosisform a diagnosis

– The results from these tests are used The results from these tests are used in conjunction with the other clinical in conjunction with the other clinical findings to help guide the clinicianfindings to help guide the clinician

– To assure accuracy with these tests, To assure accuracy with these tests, both sides should be tested for both sides should be tested for comparisoncomparison

InterventionIntervention

Acute PhaseAcute Phase– The goals during the acute phase are:The goals during the acute phase are:

Reduce pain and swellingReduce pain and swelling Control inflammationControl inflammation Regain range of motionRegain range of motion Minimize muscle atrophy/weaknessMinimize muscle atrophy/weakness Attain early neuromuscular controlAttain early neuromuscular control Maintain general fitnessMaintain general fitness

InterventionIntervention

Functional PhaseFunctional Phase– The goals for this phase include:The goals for this phase include:

Attain full range of pain free motionAttain full range of pain free motion Restore normal joint kinematicsRestore normal joint kinematics Improve muscle strengthImprove muscle strength Improve neuromuscular controlImprove neuromuscular control Restore normal muscle force couple Restore normal muscle force couple

relationshipsrelationships

Chapter 18

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