Athletic Training: Knee Injuries

Explain some basic aspects of knee anatomy

• Femoral condyles & epicondyles: medial & lateral

• Patella: Femoral sulcus, patellar tendon

• Tibial plateau w condyles

• Tibial tubercle, fibula

• Joints:

  • Tibio-femoral

  • patello-femoral

  • proximal tibio-fibular

• Ligaments:

  • Extra-articular: MCL/LCL

  • Intra-articular: ACL/PCL

• Menisci: medial & lateral

Explain knee motion: Arthrokinematics

• Hinge joint

• Flexion & extension (physiologic - voluntary control)

  • Femoral condyles roll on tibial plateaus

• Accessory movement (involuntary)

  • Tibial plateau spins & glides/slides on femoral condyles

Explain how the Q-angle is used as a screening technique

• Computed as the difference btwn:

  • A line drawn from the cener of the patella to the ASIS

  • Compared with: a line drawn from the center of the patella through the tibial tubercle

• Normal = 15-20 degrees

  • > 20: genu valgum (knock knees)

  • < 15: genu varum (bow legs)

• Excessive Q-angle is thought to be a risk factor for knee injury

Explain Patellar Tendon-related injuries that cause anterior knee pain

• Not tendon “itis”, -osis (degenerative changes) or -opathy (symptomatic)

• MOI: jumping/landing activity: eccentric loading

• S/S: point tender over tendon, proximal, mid-substance, distal, quadriceps weakness, pain upon loading quads

• Risk factors: Limited dorsiflexion, muscle weakness (gluteals), tightness of quads, hamstrings and calves

• 4 stages based on duration of symptoms

  • 1: pain after activity, w/o functional limitation

  • 2: pain during & after activity, w/o functional limitation

  • 3: prolonged pain during & after activity, w functional limitations

  • 4: complete tendon tear, requires surgical repair

• Possible Degenerative changes

  • Chronic attenuation

  • Loss of tensile stregth

  • Mucoid (pockets of fluid, gel like

  • Thickens: Fatty infilitratioon, calcification

• Management: Strengthen quadriceps (eccentric loading), Cho-pat strapping

Explain this condition: Osgood-Schlatter's Disease

• Traction apophysitis

• Adolescent condition

• Outgrow of bone from tibial tuberosity

  • Avulsion fracture, separation of TT

• Growth disorder: asymmetric, bone > muscle

Explain this condition: Chondromalacia Patellae

• Degenerative softening or wearing away of the articular cartilage underneath patella

• Compression & shear forces

• Irritation and exposure of free nerve endings

• MOI: excessive Q-angle, abnormal tracking of patella

• S/S: pain during patellar motion (quad activity)

Explain this injury: Patella Dislocation/Subluxation

• Risk factors: excessive q-angle (lateral pull), quad weakness, joint laxity (loose ligaments)

• MOI: direct blow to the knee, quick start or cutting motion when running

• Tear of the medial retinaculum or medial patello-femoral ligament (MPFL)

• S/S: pain and anormal movement about patella, patella may be out of place or spontaneous reduction, extreme pain along pedial aspect of patella, athlete may report that the knee "gave out"

• Management: PRICE, immobilize leg, refer for x-ray and reduction

• May become chronic on acute w recurrent episodes

What are the benefits of Patellar Bracing

• #1 benefit is to prevent abnormal tracking of patella

• Secondary beefits: prevent lateral displacement, control patellar tracking during activity, maintain normal sliding motion

Explain this Injury: MCL tear

• MOI: valgus loading of the knee in extension, contact vs non-contact knee mechanism

• MCL is primary restraint to valgus loading (ACL is secondary)

• Most frequent injured knee ligament

• S/S: point tender and pain over MCL upon palpation or hyperextension, swelling of medial knee, athlete states knee feels "stiff", felt and/or heard a snap or pop

• Immediate and short-term care: PRICE, place athlete on crutches, treat conservateively

• Special test: Valgus stress teast; open up medial compartment of knee, bilateral comparison

Explain this injury: ACL tear

• contact vs non-contact mechanisms

• ACL is watchdog of knee → major static stabilizer

• MOI: valgus loading w tibial rotation; and or/ anterior tibial displacement (driven forward), or hyperextension

• Prevalence:

  • 25%: damage is isolated to ACL

  • 60%: meniscal damage (medial and/or lateral)

  • 30%: articular cartilage damage

  • 30%: damage to collateral ligaments, joint capsule, or a combination of injuries

• S/S: heard/felt pop, rapid hemarthrosis: swelling in joint (golden period), stiff, warm and extremely painful

  • Hemarthrosis: joint inflammation followed by muscle guarding (protective spasm)

  • Golden peiod: 15-30 min window

• Surgical reconstruction for athletes: restores stability

• Conservative management: Not very effective → chronic ACL deficiency: knee gives out or buckles during tibial rotation

• Special Test: Lachman Test, knee @ 30 degrees flexion, grasp femur and tibia, displace tibia anteriorly, bilateral comparison, amount of movement?

Explain what is the unhappy or terrible triad

• 3 structures damaged

  • MCL rupture: Valgus loading tibia rotates outward

  • Meniscus (lateral) tear: Compression of postero-lateral tibio-femoral compartment → valgus collapse, femoral plateau contusion

  • ACL rupture: tibial rotaion and anterior displacement on femur

Explain the different theories for the gender or sex bias for ACL tears

• Anatomic: excessive Q-angle

• Hormonal: menstrual cycle release of relaxin, progesterone decrease tensile strength of CT

• Neuromuscular: slower muscle activation patterns (diminished dynamic stability)

• Genetic predisposition (collagen gene malfunction): waker collagen → decreased tensile strength

Explain the functional anatomy of the meniscus

• Structure: semilunar wedges

  • Fibrocartilage

  • Circumferential fibers (outside run longitudinally)

  • Radial fibers (inside to outside)

  • Blood vessels penetrate the outer third

• Functions:

  • Load bearing → absord and distribute loads (contact forces) over the articular surface

  • stability to joint by increasing fit and resisting AP displacements

  • Proprioception (sense position awareness and motion)

• Anatomy:

  • Medial: C-shaped

  • Lateral discoid (more mobile)

  • Stability:

    • Anterior: transverse ligaments

    • Coronary (menisco-tibial ligaments

      • MCL and capsular attachments

      • Horn attachments: root ofr spine

    • Posterior-menisco femoral ligaments

Explain this injury: Meniscal tears

• Meidal meniscus is less mobile and more often torn in ACL deficient knee

  • Location of most tears: posterior horn of meniscus (red circles)

• MOI: tears occur when knee is flexed and rotated

• Forces:

  • Compression: condyles on plateau

  • Shear: AP displacement

  • Tensile: stretch out

• Tears include radial or oblique, longitudinal or cleavage plane (internal)

  • Avulsion from root (spine)

• Healing & repair:

  • Outer 1/3 may repair itself w surgery

  • Hypovascular: no repair (degenerates)

  • Meniscetomy: removes loose fragments, trimmed

  • Repair: sutured

• S/S: joint line tenderness: posterior horn region, slow effusion (delayed swelling) hypovascular, limited ROM, popping, clicking or locking sensation, narrowing of joint space: reduces funciton

• Special Tests: Appley's Compression, McMurray's

Explain this injury: PCL

• PCL is larger and stronger than ACL

• Does not provide rotary stability for knee because it is more vertically aligned

• Prevents posterior displacement of tibia

• MOI: knee flexed, tibia driven posteriorly (dashboard injury), or hyperextension, isolated or combined w damage to postero-lateral corner, joint capsule and arcuate complex

• Special Tests: posterior drawer, displacement of tibia posteriorly, external rotation recurvatum (hyperextension

Explain this injury: Ilio-Tibial band friction syndrome (ITBFS)

• Ilio-tibial band: thick band of CT (fascia)

  • Gerdy's tubercle: attachment point on lateral tibia

• MOI: Overuse (compression & shear forces)

  • Lateral epicondyle of femur

  • Friction @ 20-30 degrees

• S/S: lateral knee pain w running, point tender, swelling

• Risk factors: Excessive Q-angle, tightness, excessive running

• Pathophysiology: friction irritates ITB, lateral synovial recess (bursae), bursitis: inflammation