The Knee Complex

1
Chapter 18

• The Knee Complex

2
Overview

• The knee joint complex is extremely elaborate and
  includes three articulating surfaces, which form
  two distinct joints contained within a single
  joint capsule the patellofemoral and
  tibiofemoral joint
• Given the frequency of knee injuries and the
  intricate nature of this joint complex,
  clinicians caring for knee injuries must have an
  extensive knowledge base

3
Anatomy

• The tibiofemoral joint
• The tibiofemoral joint consists of the distal end
  of the femur and the proximal end of the tibia
• The distal aspect of the femur is composed of two
  femoral condyles that are separated by an
  intercondylar notch
• The intercondylar notch serves to accept the
  anterior cruciate ligament (ACL) and the
  posterior cruciate ligament (PCL)

4
Anatomy

• Distal femur
• The femoral condyles project posteriorly from the
  femoral shaft
• The smaller lateral femoral condyle is
  ball-shaped and faces outward, while the
  elliptical-shaped medial femoral condyle faces
  inward
• The lateral epicondyle serves as the origin for
  the lateral head of the gastrocnemius, and the
  lateral collateral ligament (LCL)
• The medial condyle serves as the insertion site
  for the adductor magnus, and the medial
  collateral ligament (MCL)

5
Anatomy

• Femoral condyles
• The anterior-posterior length of the medial
  femoral condyle is greater than its lateral
  counterpart by about 1.7 cm
• The length of the articular surface of the medial
  femoral condyle is longer than the length of the
  lateral femoral condyle

6
Anatomy

• Proximal tibia
• The proximal tibia is composed of two plateaus
  separated by the intercondylar eminence,
  including the medial and lateral tibial spines
• The tibial plateaus are concave in a
  medial-lateral direction
• In the anterior-posterior direction, the medial
  tibial plateau is also concave, while the lateral
  is convex, producing more asymmetry, and an
  increase in lateral mobility
• The medial plateau has an approximately 50
  greater surface area than the lateral plateau,
  and its articular surface is 3 times thicker

7
Anatomy

• Patellofemoral Joint
• The patellofemoral joint is a complex
  articulation, dependent on both dynamic and
  static restraints for its function and stability
• The patella is a very hard triangular-shaped
  bone, situated in the intercondylar notch, and
  embedded in the tendon of the quadriceps femoris
  muscle above, and the patella tendon below
• The posterior surface of the patella can include
  up to seven facets, with three on the medial and
  lateral surfaces

8
Anatomy

• The patellofemoral joint functions to
• Provide an articulation with low friction
• Protect the distal aspect of the femur from
  trauma, and the quadriceps from attritional wear
• Improve the cosmetic appearance of the knee
• Improve the moment arm of the quadriceps
• Decrease the amount of anterior-posterior
  tibiofemoral shear stress placed on the knee
  joint

9
Anatomy

• The knee joint capsule
• is composed of a thin, strong fibrous membrane
• is the largest synovial capsule in the body
• A synovial membrane lines the inner portion of
  the knee joint capsule. By lining the joint
  capsule, the synovial membrane excludes the
  cruciate ligaments from the interior portion of
  the knee joint, making them extrasynovial yet
  intra-articular

10
Anatomy

• The proximal tibiofibular joint
• An almost plane joint with a slight convexity on
  the oval tibial facet and a slight concavity of
  the fibular head
• Has more motion than its distal partner

11
Anatomy

• Ligaments
• The static stability of the knee joint complex
  depends on four major knee ligaments, which
  provide a primary restraint to abnormal knee
  motion
• Anterior cruciate
• Posterior cruciate
• Medial collateral
• Lateral collateral

12
Anatomy

• The cruciate ligaments
• Are intra-articular/extra synovial because of the
  posterior invagination of the synovial membrane
• Are different from those of other joints, in
  that, they restrict normal motion, rather than
  restrict abnormal motion

13
Anatomy

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

14
Anatomy

• The anterior cruciate ligament
• One of the most important ligaments to knee
  stability
• Serves as a primary restraint to anterior
  translation of the tibia relative to the femur,
  and a secondary restraint to both internal and
  external rotation in the non-weight bearing knee

15
Anatomy

• The posterior cruciate ligament
• Provides 90-95 of the total restraint to
  posterior translation of the tibia on the femur,
  with the remainder being provided by the
  collateral ligaments, posterior portion of the
  medial and lateral capsules, and the popliteus
  tendon

16
Anatomy

• The medial collateral ligament (MCL)
• The anterior fibers of this ligament are taut in
  flexion, and can be palpated easily in this
  position
• The posterior fibers, which are taut in
  extension, blend intimately with the capsule and
  with the medial border of the medial meniscus,
  making them difficult to palpate

17
Anatomy

• The lateral collateral ligament (LCL)
• The main function of the LCL is to resist varus
  forces
• It offers the majority of the varus restraint at
  25 of knee flexion, and in full extension

18
Anatomy

• Secondary restraints include
• The structures in the posterior-lateral and
  posterior-medial corners of the knee
• The hamstrings and quadriceps
• The patellar ligament, oblique popliteal
  ligaments, and the fabella

19
Anatomy

• Menisci
• The crescent-shaped lateral and medial menisci,
  attached on top of the tibial plateaus, are
  pieces of fibrocartilage material that lie
  between the articular cartilage of the femur and
  the tibia

20
Anatomy

• Medial meniscus
• Semi-lunar or C-shaped
• Larger and thicker than its lateral counterpart
• Sits in the concave medial tibial plateau
• Wider posteriorly than anteriorly

21
Anatomy

• Lateral meniscus
• Rounder O-shaped
• Sits atop the convex lateral tibial plateau
• Smaller and thinner, than its medial counterpart
• More mobile than its medial counterpart
• Two mensicofemoral ligaments, the ligaments of
  Humphrey and Wrisberg attach to the lateral
  meniscus

22
Anatomy

• Menisci Function
• The menisci assist in a number of functions
  including load transmission, shock absorption,
  joint lubrication, joint stability and the
  guiding of movements

23
Anatomy

• Bursae
• There are a number of bursae situated in the soft
  tissues around the knee joint
• The bursae serve to reduce friction, and to
  cushion the movement of one body part over another

24
Anatomy

• Plica
• Synovial plica represents a remnant of the three
  separate cavities in the synovial mesenchyme of
  the developing knee

25
Anatomy

• Retinacula
• Formed from structures in the first and second
  layers of the knee joint
• The retinacula can be subdivided into the medial
  and the lateral retinacula for clinical
  examination and intervention purposes

26
Anatomy

• Muscles
• The major muscles that act on the knee joint
  complex are the quadriceps, the hamstrings
  (semimembranosus, semitendinosus, and the biceps
  femoris), the gastrocnemius, the popliteus, and
  the hip adductors

27
Anatomy

• Vascular supply
• The major blood supply to this area comes from
  the femoral, popliteal, and genicular arteries

28
Anatomy

• Neurology
• Femoral nerve
• Saphenous nerve
• Sciatic nerve
• Common peroneal
• Tibial

29
Biomechanics

• The tibiofemoral joint
• The tibiofemoral joint, or knee joint, is a
  ginglymoid, or modified hinge joint, which has
  six degrees of freedom
• The bony configuration of the knee joint complex
  is geometrically incongruous and lends little
  inherent stability to the joint
• Joint stability is therefore dependent upon the
  static restraints of the joint capsule,
  ligaments, and menisci, and the dynamic
  restraints of the quadriceps, hamstrings, and
  gastrocnemius

30
Biomechanics

• Patellofemoral joint
• To assist in the control of the forces around the
  patellofemoral joint, there are a number of
  static and dynamic restraints

31
Biomechanics

• The Quadriceps (Q) angle
• Can be described as the angle formed by the
  bisection of two lines, one line drawn from the
  anterior superior iliac spine (ASIS) to the
  center of the patella, and the other line drawn
  from the center of the patella to the tibial
  tubercle
• The most common ranges cited are 8-14 for males
  and 15-17 for females
• Angles of greater than 20 are considered
  abnormal and may be indicative of potential
  displacement of the patella

32
Biomechanics

• Patella-Femur Contact and Loading
• The amount of contact between the patella and the
  femur appears to vary according to a number of
  factors including
• The angle of knee flexion
• The location of contact
• The surface area of contact
• The patellofemoral joint reaction force

33
Biomechanics

• Patella Stability
• Patella stability is dependent on 2 factors
• Static restraints
• Dynamic restraints

34
Biomechanics

• Patellar Tracking
• In the normal knee, the patella glides in a
  sinuous path inferiorly and superiorly during
  flexion and extension respectively, covering a
  distance of 5-7 cm with respect to the femur
• One proposed mechanism for abnormal patellar
  tracking is an imbalance in the activity of the
  of the vastus medialis obliquus (VMO) relative to
  the vastus lateralis (VL)

35
Biomechanics

• Open and Closed Kinetic Chain Activities
• An understanding of the forces generated and the
  muscle activity employed by different exercises
  is essential for determining how to achieve
  optimal balance of muscle force, ligament
  tension, and joint compression
• Whether the motion occurring at the knee joint
  complex occurs as a closed or open kinetic chain
  has implications on the biomechanics and the
  joint compressive forces induced

36
Examination

• History
• The diagnosis of tibiofemoral and patellofemoral
  joint disorders can often be made on the history
  and physical examination alone
• With the larger number of specific tests
  available for the knee joint complex, it is
  tempting to overlook the important role of the
  history, which can detail both the chronology,
  and mechanism, of events

37
Examination

• History
• The mechanism of the injury is one of the most
  important aids in making a diagnosis
• The position of the joint at the time of the
  traumatic force dictates which anatomic
  structures are at risk for injury
• The primary mechanisms of injury in the knee are
  direct trauma, a varus or valgus force (with or
  without rotation), hyperextension, flexion with
  posterior translation, a twisting force, and
  overuse

38
Examination

• History
• There is a significant temptation to cut corners
  with a patient who presents with anterior knee
  pain, and to proceed directly to the diagnosis of
  patellofemoral pain
• Particular activities can help with differential
  diagnosis
• Complaints of pain that occur when a patient
  arises from a seated position, negotiates stairs,
  or squats, are associated with patellofemoral
  dysfunction

39
Examination

• Systems Review
• Knee pain can be referred to the knee from the
  lumbosacral region (L 3 to S 2 segments), or from
  the hip

40
Examination

• Observation
• The observation component of the examination
  begins as the clinician meets the patient and
  ends as the patient is leaving
• This informal observation should occur at every
  visit

41
Examination

• Active Range of Motion with Passive Over pressure
• Normal knee motion has been described as 0 of
  extension to 135 of flexion, although
  hyperextension is frequently present to varying
  degrees
• Passive movements, as elsewhere, can determine
  the amount of motion and the end-feel
• Resisted testing is performed to provide the
  clinician with information about the integrity of
  the neuromuscular unit, and to highlight the
  presence of muscle strains

42
Examination

• Palpation
• For palpation to be reliable, the clinician must
  have a sound knowledge of surface anatomy, and
  the results from the palpation exam should be
  correlated with other findings

43
Examination

• Functional Tests
• Functional outcome following knee injury must
  consider the patients perspective, and not just
  objective measurements of instability
• Functional motion requirements of the knee vary
  according to the specific task
• A number of commonly used rating scales can be
  used to assess knee function

44
Examination

• Special Tests
• Special tests are merely confirmatory tests and
  should not be used alone to form a diagnosis
• The results from these tests are used in
  conjunction with the other clinical findings to
  help guide the clinician
• To assure accuracy with these tests, both sides
  should be tested for comparison

45
Intervention

• Acute Phase
• The goals during the acute phase are
• Reduce pain and swelling
• Control inflammation
• Regain range of motion
• Minimize muscle atrophy/weakness
• Attain early neuromuscular control
• Maintain general fitness

46
Intervention

• Functional Phase
• The goals for this phase include
• Attain full range of pain free motion
• Restore normal joint kinematics
• Improve muscle strength
• Improve neuromuscular control
• Restore normal muscle force couple relationships