Articular Cartilage
avascular, receives nutrients via diffusion
Meniscus
- C-shaped wedges of fibrocartilage between tibial plateaus and femoral condyles
- 70% type I cartilage
- Peripheral 1/3 has rich blood supply–> tears in this area (longitudinal tears) have increased change for healing
*Inside 2/3 have no blood supply–> cannot heal
Collateral ligaments
ACL- prevents tibia from moving forward
PCL- prevents tibia from moving backward
LCL- extremely stable
MCL
What to look for on inspection?
- effusion
- inflammation
- varus deformity
- valgus deformity
- patellar alignment
- thigh atrophy
- Q angle
When does an effusion appear with ACL and meniscal injury?
- ACL results in effusion <24 hours
- Meniscal injury results in effusion 24-48 hours
Varus deformity a/w what?
Osteoarthritis (bow-legged)
Valgus deformity a/w what?
Inflammatory arthritis
Patellar alignment–> which direction does it deviate?
- femoral torsion/anteversion (MCC of in-toeing in children from ages 3-10)
- knee dislocation results in lateral deviation of the patella
Normal Q angle?
- normal is ~15 degrees
- Increased Q angle increased risk of patellar subluxation and patellofemoral syndrome
- Increased Q angle with femoral anteversion/tibial external torsion (toe in) and tight lateral retinaculum
What is the Q angle?
- line from ASIS to patella
- line from tibial tuberosity to the patella
Measure the angle between those 2 lines.
What should you think of with joint line tenderness?
- medial meniscus tear
- osteoarthritis
What is the pes anserine bursa?
-25 mm area near the medial tibial plateau
What tendons insert at the pes anserine bursa?
-SGT (Sartorius, Gracilis, and semiTendinosus)
How to test for pes anserine bursitis?
-Resisted adduction–> think of the function of the muscles that attach there
Palpation
- Superior pole of patella–> quad tendonitis
- Inferior pole of patella–> patellar tendonitis (jumper’s knee)
- Popliteal fossa–> baker’s cyst, usually results from knee effusion d/t posterior meniscal tear
- Pre-patellar bursa on anterior patella–> “housemaid’s knee”
Plica Syndrome
- Plica is an embryological remnant
- Plica snaps over medial epicondyle
Where do knee effusions collect?
-large effusions collect in the suprapatellar fossa (25-30ml)
Tests/signs for effusion?
- “Milking” techinique/wave sign: tap lateral compartment and look for fluid wave on medial side
- Ballottement sign: compress all fluid to center of knee, force down patella with index finger, + test with clicking or tapping sensation (10-15ml)
- Abnormal “heel to buttock” measurement
What is the normal ROM of the knee?
What is the function ROM of the knee?
- Normal: 0-145 degrees
- Function knee flexion is 110 degrees
- 65 degrees KF needed for ambulation at normal pace
- 90 degrees KF needed to ascend stairs “step over step”
- 110 degrees KN needed to arise from seated position
Gait exam for knee pathology
- Typically antalgic gait in knee OA- i.e. shortened stance time on affected leg
- Heel/toe walking
- “duck-walking” effectively excluded significant intra-articular knee pathology
How to assess MCL?
- Valgus stress test- hand on lateral knee and medial tibia; apply stress to lateral knee
- check with knee flexed 25-30 degrees and in full extension
- compare to opposite side
- Increased laxity with knee flexed indicated MCL injury
- Increased laxity with knee in full extension usually indicated other ligaments are injured as well (i.e. ACL)
How to assess LCL?
- Varus stress test- hand on medial knee and lateral leg; apply stress on medial knee to open up lateral joint space
- Check with knee in full extension and 25-30 degrees of extension
- Increased laxity with knee flexed indicated LCL injury
- Increased laxity with knee in full extension usually indicated other ligaments are injured as well (i.e. ACL)
If a patient reports a “pop” and knee effusion within 24 hours, what should you suspect?
-ACL injury
- Usually non-contact injury
- May also result in knee instability and “giving out” episodes
Do ACL injuries need to be repaired?
No, but it may contribute to early arthritis.
What is the best test for ACL injury?
- Lachman Test- knee flexed 25 degrees, grab thigh with one hand and tibia with other hand; apply anterior force on tibia and posterior force on femur–> shucking motion
- Positive test is lack of firm endpoint or increased translation
*Most sensitive test for ACL injuries.
What are 2 other tests for ACL injury?
- Anterior Drawer Sign: knee flexed to 90 degrees, sit on patient’s foot, pull tibia forward with both hands; + test is increased movement compared to opposite leg
- Pivot shift test: Valgus and internal rotation force applied to knee in extension; hold theses forces while flexing the knee; + test reveals subluxation of tibia in anterior and lateral direction (usually done under anesthesia)
What should you think of with “dashboard” injury?
- PCL injury
* isolated injury to PCL is rare
What are the 3 tests for PCL injury?
- Posterior drawer test: same as anterior drawer sign except push tibia in posterior direction with both hands
- Thumb sign: in complete PCL injury the tibia rests posterior and area to place thumbs on tibia plateau decreases; normally ~1 cm
- Posterior sage sign: posterior displacement of tibia
What is a positive test for meniscal injury?
Pain AND clicking!
What are the tests for Meniscal injury?
- McMurray test
- Appley’s compression/grind test
- Bounce Home test
McMurray test?
- Flex the knee with foot externally rotated, extend knee (stresses medial meniscus)
- Flex knee with foot internally rotated, extend knee (stresses lateral meniscus)
+ test is pain AND clicking
Appley’s compression/grind test?
-patient prone, knee flexed to 90, downward force with rotation applied to foot
Bounce Home test?
- patient supine, grasp heel and maximally flex knee, passively let knee fall to full extension
- if pain is reproduced and/or knee does not fully extend (i.e. knee “bounces home” to full extension), this may indicate meniscal injury
Patellofemoral Pain Syndrome
- MCC of knee pain in outpatient setting
- Common in runners
- Patient reports increased pain with stairs, squatting, etc.
*Think young patient with bilateral knee pain
What causes PFPS?
- Imbalance of forces which control patellar tracking during knee flexion/extension
- Need to assess kinetic chain to determine etiology (i.e. IT band, hip abductors, pes planus, etc.)
What are 2 signs for PFPS?
- Theater sign: increased pain and stiffness after prolonged sitting
- Circle sign: patient often have difficulty localizing area of pain and make a circle around anterior knee with their finger
What is the J sign?
- evaluates patellar tracking
- Normally patella moves slightly lateral to medial to lateral position with knee flexion
- Increased arc of movement indicated patellar tracking problem (i.e. patellofemoral syndrome)
- assess with single leg squat and stand.
- may also assess with seated or supine knee flexion/extension
When is one time you make see lateral OA?
-Flat feet
What is the patellar grind test?
- knee in full extension, quad relaxed, apply inferior force on patella and ask patient to contract quad
- positive test is reproduction of pain, compared side to side
What is the medial glide test?
-patella is divided into 4 quadrants; with knee extended force patella medially and assess degree of displacement
- less than 1 quadrant indicated tight lateral structures
- displacement of 3 or more quadrants indicated hypermobility
What is the Patellar tilt test?
- knee extended, grasp patella with thumb and finger, apply downward force on medial aspect
- positive test if lateral patella is fixed and not elevated past zero degrees in horizontal plane–> indicates tightness of lateral structures
Patellar instability Test?
- Patellar apprehension test: patient sitting, extend knee and move patella laterally, then flex knee to 30 degrees while maintaining lateral force on patella
- Positive test is feeling of apprehension or pain and indicates patellar instability/subluxation
Hamstring strain/tear symptoms?
- Hamstring strain/tear can cause posterior knee pain
- Reproduction of pain with resisted knee flexion usually confirms the diagnosis
What does the popliteal angle assess?
- test for hamstring tightness
- test with 90 degrees of hip flexion
- extend the knee as far as possible
- normal is to lack 10-30 degrees from full extension in children, may be more in adults
- greater than 50 degrees lacking is always abnormal