Table of contents
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Anatomy
- Complex joint:
- No rotary motion in full extension.
- Rotation enabled on flexion: up to 40 degree of rotation at 90° flexion (relaxes tendons)
- Above Knee:
- Vastus medialis - pulls patella medially (prevents lateral dislocation)
- Vastus intermedius
- Vastus lateralis
- Medial: (Aka Pes anserinus)
- Sartorius
- Gracilis
- Semitendinosus
- Tendon inserts on the oblique popliteal ligament. Adding posterior mobility to the ligament and medial meniscus during flexion.
- Lateral:
- Iliotibial tract
- Tendon of biceps femoris.
- Static Stabilizers (Ligaments).
- MCL
- Most commonly injured ligament.
- Ligament is taught only in extension.
- Limit forward glide of tibia on femur and limit rotation + abduction.
- Collaterals are twice as effective in limiting rotational laxity as cruciate ligaments.
- LCL
- Posterior Capsule (prevents against anteromedial or anterolateral rotatory instability).
- Cruciate ligaments:
- Extend from intercondylar fossa of femur to intercondylar eminence of tibia.
- Named on basis of their tibial attachment.
- ACL
- Prevents anterior displacement of tibia and excessive lateral mobility in flexion or extension.
- Prevents hyperextension of knee.
- ACL tears are rarely isolated, often associted with MCL tears.
- Plentiful vascular supply.
- When ruptures, hemarthrosis is almost always present!
- PCL
- Primary static knee stabilizer against rotation.
- if ruptured, anteposterior and mediolateral instability can occur.
- If ruptured, rarely isolated, usually associated with serious knee injuries.
- MCL
- Dynamic Stabilizers (Tendons/muscles)
- Quadriceps tendon - dynamic stabilizer
- Combination of tendons: vastus medialis, intermedialis, lateralis, and rectus femoris.
- Primary dynamic stabilizer of knee.
- Attaches to patella and continues distally to tibial tubercle as patellar tendon.
- Pes anserinus (medial)
- Conjoined tendons:
- Gracilis, sartorius, and semitendinosus.
- Stabilize against excessive rotary and valgus motion.
- Conjoined tendons:
- Semimembranosis (lateral)
- Tendon has three extensions:
- To posterior capsule (posterior oblique ligament), and tightens the capsule when stressed.
- Posterior horn of medial meniscus (pulls posteriorly during flexion)
- Medial tibial condyle - serving to flex and internally rotate the knee.
- Tendon has three extensions:
- Other Lateral Stabilizers
- 1. Iliotibial band - inserts lateral tibial condyle.
- 2. Biceps femoris - lateral stability, knee flexion + external rotation.
- 3. Popliteus muscle (posterir muscle inserting with a Y-shaped tendon called arcuate ligament, another limp inserts into posterior portion of lateral meniscus providing posterior mobility of lateral meniscus during flexion).
- Quadriceps tendon - dynamic stabilizer
- Imaging:
- AP
- Lateral
- Oblique (for tibial plateau and spines).
- Otherviews:
- Skyline (patellar view of supine patient with knees slightly flexed - beam down to feet).
- See Patella relationship to femoral condyles.
- Tunnel view (patient lying prone, knee flexed to 40° from vertical)
- See intercondylar notch.
- Skyline (patellar view of supine patient with knees slightly flexed - beam down to feet).
Ottawa Knee Rules
Knee Xray series for knee injury plus any of these findings:
1. Age >55y
2. Isolated tenderness of patella. (no bone tenderness other than patella)
3. Tenderness at head of fibula.
4. Inability to flex to 90°
5. Inability to bear weight both immediately and in ER (4 steps) (Transfer weight twice on each leg - limping allowed) |
Proximal Tibia Fractures
- Fractures can be classified:
- Intra-articular - "Condylar" (tibial plateau)
- Extra-articular
- Tibial spine
- Tubercle
- Subcondylar Regions
- Classification:
- Schatzker classification:
- NOTE: tibial plateau fracture defined as >4mm of inferior displacement.
- Types I to III result of low energy trauma
- Types IV to VI is high energy.
- Type 1 - lateral condyle (aka splint fracture)
- typically young patients because bone resists depression.
- Suggests lateral menistal injury
- Type II - lateral condyle + depression (aka split-depression)
- Usually people >30yo bc subchondral bone is weaker.
- Type III - Depression of lateral condyle.
- Likely joint is unstable.
- Type IV - Medial condyle (need higher force to fracture medial condyle)
- High energy - high incidence of cruciate ligaments and popliteal artery injuries.
- May be associated with # of intercondylar eminence.
- Type V - Bicondylar
- Possess varying articular depression and displacement.
- Medial is usually split, and lateral is often depression (can be split)
- Type VI - Bicondylar + fracture between diaphysis-metaphysis
- High energy, often comminuted.
- Schatzker classification:
- Mechanism:
- Fall from height (20%)
- Automobile-pedestrian where car bumper strikes over proximal tibia. (50%)
- Lateral Tibial plateau #'s: abduction force on the leg.
- Medial plateau: adduction
- Imaging:
- If clincally suspected but negative xrays: do CT!
- Can do tibial plateau view (tibial plateau slopes down anatomically)
- Look for avulsion fractures:
- fibular head
- femoral condyles
- intercondylar eminence
- Look for widened joint space (fracture of opposite condyle)
- Look for knee effusion (occult fracture, peripheral meniscus, ACL/PCL, patellar dislocation)
- Knee effusion appears as distance between two fat pads just superior to patella on lateral view
- Tx
- Immobilize with long-leg posterior mold
- Need operative fixation.
- (CAN treat non-operatively, but very high degree of complications)
- Complications:
- Loss of ROM (prolongued immobilization)
- Degenrative arthritis
- Angular deformity
Tibial Spine Fractures
- Isolated uncommon: usually 8-14yo.
Patellofemoral
- Atraumatic
- Mid-ROM pain 45-90° flexion.
- Sitting long periods.
- Pain with walking down stairs.
- Mechanism: Young people that grow rapidly, associated with patellar maltracking.
- Exam:
- Can squat, but mid-ROM pain.
- J-sign: sitting on bench - extend knee and it goes laterally.
- Lean on Patella pushing it laterally --> pain.
- "Clarke's Test" put hand on quad tendon.. push down against quads and ask patient to contract quad --> pain.
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