Acute Knee Flashcards
What is the difference between structural instability and functional instability?
Structural: jt instability based on TESTING ONLY, not pt function
Functional: jt instability that affects FUNCTION
For a patient with a suspected single ligament injury to the knee, would you expect them to have SINGLE plane instabilities or MULTIPLANAR instabilities?
Single plane Instabilites: excessive ant/post glide or varus/valgus rotations
*Result of single lig injury
For a patient with suspected multiple ligament injuries to the knee, would you expect them to have SINGLE plane instabilities or MULTIPLANAR instabilities?
Multiplanar instabilities (rotary instability)
What is a common combination of injuries to the knee? (3 structures)
- ACL
- MCL
- Lateral meniscus
What is the involved lig for anterior instability?
ACL
What is the involved lig for post instability?
PCL
What is the involved lig for medial instability?
MCL
What is the involved lig for lateral instability?
LCL
What are 3 clinical tests for ANTERIOR instability? (ACL = involved lig)
- Lachman’s
- Anterior Drawer sign
- Lever sign
What are 3 clinical tests for POSTERIOR instability? (PCL = involved lig)
- Posterior drawer
- Posterior sag sign
- Quad active
What is a clinical test for MEDIAL instability (MCL = involved lig)
Valgus stress test
*Test in full ext 1st, and then 25 deg flex
What is a clinical test for LATERAL instability (LCL = involved lig)
Varus stress test
*Test in full ext 1st, then 25 deg flex
Which of the ACL clinical tests has the highest diagnostic accuracy?
Lachman’s
Which 2 of the PCL clinical test have the highest diagnostic accurary?
- Posterior sag sign
- Posterior drawer
When performing a valgus stress test to test the integrity of the MCL, you find that at 0 deg, there is medial joint line gapping, suggesting a positive test. You therefore suspect a combined lig injury. What lig(s) do you suspect are injured?
- MCL
- LCL
When performing a valgus stress test to test the integrity of the MCL, you find that at 0 deg, there is no medial joint line gapping, indicating a neg test. You go on to test at 25 deg and there is medial joint line gapping, indicating a positive test. What lig(s) do you suspect are injured?
- MCL
When performing a varus stress test to test the integrity of the LCL, you find that at 0 deg, there is medial joint line gapping, suggesting a positive test. What lig(s) do you suspect are injured?
- LCL
- ACL
When performing a varus stress test to test the integrity of the LCL, you find that at 0 deg, there is no medial joint line gapping, indicating a neg test. You go on to test at 25 deg and there is medial joint line gapping, indicating a positive test. What lig(s) do you suspect are injured?
- LCL
Rotatory instability involves ___ rotation around an abnormal ___ axis.
- Tibial
- vertical
What are the 5 possible injured structures involved with ANTEROLATERAL instability?
- ACL
- ALL
- Lateral capsule
- LCL
- Posterolateral complex (PLC)
What abnormal movement is demonstrated with anterolateral instability?
Lateral tibial plateau moves in an ANTERIOR and INTERNALLY ROTATED direction w/ respect to femur
What 4 clinical tests could you do for anterolateral instability?
- Lachman’s
- Lateral pivot shift test
- Varus stress test
- Anterior drawer w/ tibia INTERNALLY rot
What are the possible injured structures involved with anteromedial rotary instability?
- ACL
- Medial capsule
- MCL
- OPL (oblique popliteal lig)
- POL (Posterior oblique lig) - post to MCL
What abnormal movement is demonstrated with ANTEROMEDIAL instability of the knee?
The MEDIAL tibial plateau moves in an ANT and EXT ROT direction w/ respect to femur
What are 3 clinical tests for ANTEROMEDIAL instability of the knee?
- Lachman’s
- Valgus stress
- Anterior drawer w/ tibia ext rot
What are the 4 possible injured structures involved with Posterolateral rotary instability?
- PCL
- LCL
- Post Capsule
- PLC (Posterolateral corner)
What are 3 clinical tests you can perform for POSTEROLATERAL instability of the knee?
- Posterior drawer test
- Posterior sag sign
- Varus stress test
What abnormal movement is demonstrated with POSTEROLATERAL instability of the knee?
Lat tibial plateau moves in a POST and EXT ROT direction w/ respect to femur
What are the 5 possible injured structures involved with POSTEROMEDIAL rotary instability?
- PCL
- MCL
- Post Capsule
- OPL (oblique popliteal lig)
- POL (post oblique lig)
What abnormal movement is demonstrated with POSTEROMEDIAL instability of the knee?
The medial tibia plateau moves in a POST and INT ROT direction w/ respect to the femur
What are 3 clinical tests you can perform for POSTEROMEDIAL instability of the knee?
- Posterior drawer
- Posterior sag sign
- Valgus stress test
Assign a grade classification to the lig/capsule injury described below:
Microtears in lig w/ no apparent change in laxity compared to opposite knee. Still painful!
Grade I (mild)
Assign a grade classification to the lig/capsule injury described below:
- 33-66% of the lig is torn and capsular damage
- 0-5 mm greater jt gapping than opp limb w/ FIRM end-feel
Grade II (moderate)
Assign a grade classification to the lig/capsule injury described below:
- 66-99% of lig is torn and capsular damage
- 5-10 mm greater jt gapping than opp side w/ SOFTENED end-feel
Grade II+ (severe)
Assign a grade classification to the lig/capsule injury described below:
- 100% lig torn and damage to capsule
- > 10mm gapping compared to opp side, w/ NO end-point
Grade III
What are 5 non-surgical indications for knee ligament injuries?
Basically, what are reasons that would indicate that surgery is not a good option?
- Little exposure to high risk activities (cutting, pivoting, jumping)
- > 40 yo
- Severe OA
- Unwillingness to comply w/ surgical rehab
- Being a “potential coper”
What are 3 indications that you WOULD perform surgery on someone w/ ligamentous injury to the knee?
- Functional instability: repeated episodes of giving way (non-coper)
- Desire to return to high ACL demand activity
- Multiple structures involved in injury
What is a potential problem of pursuing the non-surgical route for knee ligament injuries?
Recurrent episodes of knee instability/ “giving way” can lead to progressive OA and damage to menisci and articular cartilage
What is the general rule of the key question: “to do surgery or not to do surgery?”
The younger the pt & the higher level of demand on knee jt, the greater risk for future joint damage w/o surgery.
What is the difference between arthroscopic surgery and arthotomy?
Arthoscopic surgery is completed w/ a scope into the joint
Arthrotomy surgery is completed through open incision
What are potential tissue options for an AUTOgraft ligament reconstruction of the knee?
patellar tendon, HS tendon, quad tendon (from SELF)
What are potential tissue options for an ALLOgraft ligament reconstruction of the knee?
Freeze-dried material obtained from cadaver: patellar/HS/quad/achilles tenodn, fascia lata
T or F: Current evidence (2016, 2017, 2018) shows that autografts are superior to allografts w/ respect to graft failure, pt reported outcomes, and return to sport in YOUNG, ACTIVE, HS/COLLEGE STUDENTS.
True.
T or F: evidence indicates that allograft failure rates are higher in pts < 40 yo
True.
What is the GOLD STANDARD for ACL reconstruction AUTOgrafts?
Patellar tendon (central 1/3)
Compare the advantages and disadvantages for using a patellar tendon as an autograft for ACL reconstruction.
Advantages:
- high tensile strength & stiffness
- can obtain a rigid graft fixation on both graft ends
- bone plugs heal w/in 8 weeks
- clinical studies indicate GOOD, not excellent short & long-term results
Disadvantages:
- higher incidence of ant knee pn post-surgery
- higher rate of arthrofibrosis (build-up of scar tissue)
Compare the advantages and disadvantages for using a hamstring tendon autograft for an ACL reconstruction.
Advantages:
- No disruption to extensor mechanism of the knee, like with patellar tendon
- decreased surgical time
Disadvantages:
- BIGGEST issue is less graft fixation strength on the femoral graft end (QUIZ Q)
- Soft tissue healing in bone tunnel: up to 12-16 wks
- Pn/weakness of hamstrings (recall that hamstrings are ACL agonists)
Compare the advantages and disadvantages for using a QUADRICEPS tendon autograft for an ACL reconstruction.
ADVANTAGES:
- less disruption to knee extensor mechanism
- less harvest site morbidity
- larger graft cross-sectional area
DISADVANTAGES:
- possible suprapatellar pouch injury
- requires proper tensioning
- pain/weakness of quads
T or F: When a patellar tendon is used as an autograft for ACL reconstruction, it is ~ 37% stronger than native ACL when implanted
True.
T or F: A quadrupled HS tendon graft is ~91% stronger than native ACL and ~ 39% stronger than patellar tendon autograft
True.
HS graft is multistrand (3-4 strands braided together)
Quad tendon graft has larger cross-sectional area and higher ultimate load to failure than patellar tendon graft
Identify 4 functions of the meniscus
- Attenuate joint reaction forces between femur and tibia by inc SA (pressure = force/area)
- Increase joint congruence, thus inc joint stability
- Lubrication
- Guide knee motion
T or F: Removing meniscus increases contact forces by 230%
True.
Meniscus removal can lead to OA.
Describe the vascular supply to the meniscus
Outer 1/3 (Red zone): richest blood supply via coronary ligs
Central 1/3 (Intermediate zone): limited blood supply
Inner 1/3 (white zone): NO blood supply
Decreases w/ age!
What is the MOI for a meniscus injury?
Rotation of flexed knee over a planted foot
*Often combined with lig injury
What are the 6 types of meniscus tears?
- Radial: most common
- Horizontal: typically not repairable
- Flap: tx depends on location & size
- Parrot beak: typically unstable, requires surgery
- Longitudinal: can heal if in outer 1/3, if large enough than surgery is required to repair or remove since it can become bucket-handle
- Bucket-handle: results in knee locking
What is the most common type of meniscus tear?
Radial
**Usually NOT repairable
What are the KEY FINDINGS during the time of possible MENISCUS injury?
- “Pop” (may)
- Pn localized to jt line
- “Catching” or “locking”, cannot fully straighten/bend
- Some swelling, but NOT rapid onset
- After few days, pts will often be able to perform ADLS w/o pn, BUT will have pn esp w/ ROT over fixed foot
What would you include in your physical exam if you suspect a meniscus injury?
- Joint line tenderness
- McMurray’s
- Thessaly
- Meniscus Cluster Exam:
- Joint locking
- Joint line tenderness
- McMurray’s
- Pn w/ flex
- Pn w/ hyperextension
T or F: suturing following a meniscus tear is most likely to heal if tear is in RED or INTERMEDIATE zone
True.
What are 2 reasons that a pt would need a meniscetomy?
- tear is too long
- tear is in region of poor vascularity
When would a meniscus allograft transplantation be indicated?
Total meniscectomy
What direction is post common for a patellar dislocation?
Lateral
What age range and sex are patellar dislocations most common?
10-17 yo
Females
What are the MOIs for patellar dislocations?
- Contact OR Non-contact
- Often assoc w/ medial rot/add of femur over fixed foot
*May be related to trochlear dysplasia (shallow or absent trochlear groove)
What are clinical sxs of a patellar dislocation?
- Acutely, patella will likely be LATERAL to lateral femoral condyle and knee flexed
- Patella will often self-relocate w/ ext (causes “pop”)
- Rapid onset of hemarthrosis (bleeding into jt) following relocation
- Pain
What knee structures could be injured as a result of patellar dislocation?
- Medial patellofemoral lig (MPFL)
- Medial retinaculum
- Osteochondral injury (need proper imaging: merchant view)
What should tx consist of for a pt with acute patellar dislocation?
- Typically immobilized initially (2-4 wks) in knee immobilizer brace
- WBAT on crutches
- Early ROM = important in maintaining articular cartilage health
- Progression to patella-stabilizer bracing as soon as comfort permits
- Progression to strengthening exercises based on impairments
- Movement retraining
What are surgical intervention options following patellar dislocation?
Soft tissue procedures:
- MPFL reconstruction (often gracilis or semitendinosis)
Bony procedures:
- Trochleoplasty: deepening on trochlea (if trochlear dysplasia)
- Distal realignment
- Medializing tibial tubercle (Elmsie-Trillat)
- Elevating tibial tubercle (macquet)
- Medializing and elevating tibial tubercle (fulkerson)
What are the 5 criteria included in the CPG for determining when to order radiographs following an acute knee injury?
ONE or > of the following:
1. > 55 yo
2. Isolated patellar tenderness w/o other bone tenderness
3. Fibular head tenderness
4. Cannot flex to 90 deg
5. Unable to WB immediately and in ED for 4 steps
