Ch 4 - MSK: Knee Anatomy & Clinical Tests Flashcards
Describe normal ROM of the knee.
- Flexion: 135°
- Extension: 0°
- IR: 10°
- ER: 10°
Describe muscles and innervation of knee extension.
• Quadriceps (femoral n: L2, L3, L4): – Rectus femoris – Vastus lateralis – Vastus intermedius – Vastus medialis obliquus
Describe muscles and innervation of knee flexion.
• Hamstrings – Semimembranosus – Semitendinosus – Biceps femoris ■ Long head ■Short head • Sartorius • Gracilis • Gastrocnemius
Describe muscles and innervation of knee medial rotators.
- Semitendinosus
- Semimembranosus
- Sartorius
- Gracilis
Describe muscles and innervation of knee lateral rotators.
Biceps femoris
■ Long head
■Short head
Describe muscles and innervation of unlocking knee.
Popliteus
What are the compartments of the knee?
Medial femoral–tibial
Lateral femoral–tibial
Patellofemoral
What is the Q angle?
Formed by the long axes of the femur and the tibia and reflects the natural valgus attitude of the knee
– Males: 13°
– Females: 18°
What is Knock-kneed?
Genu valgum
Excessive valgum of the knees
What is bow-legged?
Genu varum
Excessive varum of the knees
What is back-kneed?
Genu recurovatum
Hyperextension at the knees
Describe the origin and insertion of the ACL.
Origin: medial aspect of the lateral femoral condyle
Travels: anteromedially in intercondylar notch
Insertion: medial tibial eminence
What is the function of the ACL?
- Primary function is to limit anterior tibial translation
- Prevents posterior translation of the femur and hyperextension
- Limits IR of femur when the foot is fixed and knee is locked
The ACL tightens with __ and loosens in __.
The ACL tightens with full extension/femoral ER and loosens in flexion/IR.
In flexion, the ACL draws the femoral condyles ____>
Anteriorly
What does an ACL deficient knee cause?
Inc pressure on posterior menisci
Describe the origin and insertion of the PCL.
Origin: anterolateral aspect of the medial femoral condyle
Travels: intercondylar notch
Inserts: posterior aspect of tibial plateau
What is the function of the PCL?
Restrain posterior tibial translation
PCL is looser in ___ and tighter in ___.
PCL is looser in extension and tighter in flexion.
In extension, the PCL pulls the femur __.
Posteriorly
What does a PCL deficient knee cause?
More force on the patellofemoral joint
What causes tension on the MCL?
Full extension
Abduction stress in flexion
When is there peak stress on the LCL?
Adduction when the knee is at 70° flexion
What does the posterior capsule restrict?
Knee hyperextension
What is the origin and insertion of the oblique popliteal ligament?
Origin: semimembranosus tendon
Insertion: capsule and lateral meniscus
What is the function of the oblique popliteal ligament?
Strengthens the fibrous posterior capsule and resists knee extension
What is the function of the arcuate popliteal ligament complex (APLC)?
- Provides attachment for the posterior horn of the lateral meniscus
- Reinforces the lateral aspect of the knee and gives posterior lateral rotary stability
- Restrains posterior tibial translation
What can the acuate popliteal ligament complex (APLC) be mistaken for?
Rear of the posterior horn of the lateral meniscus on MRI
What is the function of the medial and lateral meniscus?
Deepen the articular surface area of the tibia to provide more stability for the femoral condyles and increased force dispersion to the tibial plateau
Describe the vascularization zones of the menisci.
- Outer 1/3 of the menisci is well vascularized
* Inner 2/3 is poorly vascularized and usually cannot be surgically repaired
Describe the medial meniscus.
- Longer than the lateral meniscus
- “C” shaped
- Peripheral border is attached to a portion of the MCL
Describe the lateral meniscus.
- “O” shaped
- Larger area than the medial meniscus
- Joined to the medial femoral condyle by the posterior meniscofemoral ligament
What are the anterior bursas of the knee?
Prepatellar
Suprapatellar
Deep infrapatellar
Superficial or subcutaneous infrapatellar
What is the most commonly damaged anterior bursa of the knee?
Prepatellar
Which anterior bursa of the knee communicates with the joint capsule?
Suprapatellar
What are the tendons of the Pes anserinus bursa?
Sartorius
Gracilis
Semitendonosus
Where can a Baker’s cyst be found?
Posterior bursa b/w medial gastroc and semimembranosus tendons
Describe the McMurray’s test setup.
– Dx posterior meniscal tears
– The patient lies supine with the knee flexed
– The examiner palpates the medial and lateral joint
Describe the McMurray’s test for medial meniscus.
- Tibia ER, valgus stress, slowly extend the knee
* (+) torn medial meniscus with audible or palpable click and pain at the medial joint line
Describe the McMurray’s test for lateral meniscus.
- Tibia IR, varus stress, slowly extend the knee
* (+) torn lateral meniscus with audible or palpable click and pain at the lateral joint line
Describe an Apley’s grind test.
- Dx meniscus tear
- Prone, knee flexed to 90°
- Force downward on the heel, compressing the menisci between the femur and tibia, then rotate tibia
- (+) pain in medial or lateral compartment
Describe an Apley’s distraction test.
- Dx MCL or LCL damage
- Prone, knee flexed
- Traction force while IR and ER tibia
- Pressure on the menisci is reduced
- (+) pain indicates ligamentous damage
Describe the Bounce home test.
- Dx dec knee extension
- Supine, flex knee while holding the heel then passively extend knee
- (+) full extension not attained, and rubbery resistance is felt
Describe the patellofemoral grind test.
- Dx patella articulating surfaces quality
- Supine, legs neutral
- Push patella distally and contract the quadriceps against the resistance on the patella
- (+) pain and crepitation on patella movement
Describe the anterior drawer test.
- Dx integrity of ACL
- Supine, knees flexed to 90°, foot stabilized, grasp knee and draw tibia forward
- (+) tibia slides from under the femur with no distinct endpoint
Why is the anterior drawer test not very sensitive?
Hemarthrosis, hamstring spasm, and posterior capsule can limit forward movement of the tibia
Describe the Lachman’s test.
- Dx ACL and anterior knee integrity
- Supine, knee flexed 15° to 30°
- Stabilize distal femur and apply anterior force to proximal tibia
- (+) anterior movement with no distinct endpoint
- Partial ACL tear: soft endpoint
What can cause a false negative in anterior drawer test?
Hamstring activity
Torn meniscus blocking tibial motion
Describe a Pivot shift test.
- Dx anterolateral rotary instability and ACL injury
- Tibia IR, valgus stress and axial load applied
- Begin in full knee extension and gently flex the knee
- (+) Anterolateral subluxation of the lateral tibial plateau
Describe the posterior drawer test.
- Dx PCL integrity
- Supine, knees flexed to 90°, foot stabilized, grasp knee and push tibia backward
- (+) tibia slides backward on the femur
Describe the Sag test.
- Dx PCL integrity
- Supine, knee flexed 90°, foot on exam table
- (+) tibia is displaced posteriorly