Soft Tissue Knee Injuries Flashcards
Function of menisci?
Distribute load from the convex femoral condyles to the relatively flat tibial articular surfaces
Differences between medial and lateral menisci?
Medial plateau is more concave and the medial meniscus is fixed whilst LATERAL MENISCUS is MORE MOBILE
Briefly describe movement of the knee joint
Due to shape and soft tissues, knee pivots on medial compartment, through flexion and extension
Tibia internally rotates on flexion and externally rotates on extension
Which meniscus is under the greatest amount of shear stress?
Medial meniscus
Ligaments of the knee and their functions?
Medial collateral ligament (MCL) - resists valgus stress
Lateral collateral ligament (LCL - resists varus stress
Anterior cruciate ligament (ACL ) - resists anterior subluxation of the tibia and INTERNAL ROTATION OF THE TIBIA IN EXTENSION
Posterior cruciate ligament (PCL) - resists posterior subluxation of the tibia, i.e: anterior sublixation of the femur and hyperextension of the knee
Describe the posterolateral corner of the knee
PCL and LCL with popliteus and other smaller ligaments resist external rotation of the tibia in flexion
Consequences of rupturing the different ligaments of the knee?
MCL rupture - valgus instability
ACL rupture - rotatory instability
PCL rupture - recurrent hyperextension or instability descending stairs
Posterolateral corner rupture - varus and rotatory instability
Multi-ligament injury - gross instability
Meniscal tears scenarios?
Younger patient - sporting injury or getting up from a squatting position; also, half of ACL ruptures are accom. by a meniscal tear
Older patients (>40 years) - can get atraumatic spontaneous degenerate tears
Ix for meniscal tear?
MRI - menisci should be uniform black triangle (look like a bow-tie); there should be no lines within the triangles
Which meniscus tears most commonly?
Medial meniscal tears are 10X more common
Why do meniscal tears have limited healing potential?
Only the peripheral third of the menisci have a blood supply, i.e: radial tears will not heal
Management options of meniscal tears?
Acute peripheral tears in younger patients - arthroscopic repair can be considered with extensive rehab (40% failure rate)
For mechanical symptoms (painful catching/locking) in irreparable tears or failed meniscal repair - arthroscopic menisectomy
Patterns of different meniscal tears?
Longitudinal tear (if near the edge, it may heal)
Bucket handle meniscal tear
Radial tear (will not heal)
Parrot beak tear
ADD IMAGE MENISCAL TEARS
Describe the presentation of a bucket handle meniscal tear
ACUTE LOCKED KNEE signifies a displaced bucket handle meniscal tear; patient will also have a 15 degree springy block to extension (unable to straighten leg)
If the knee remains locked, they may develop a fixed flexion deformity (AKA flexion contracture - unable to straigthen leg)
Management of a bucket handle meniscal tear?
Urgent surgery required as, if the knee remains locked, they may develop a fixed flexion deformity
If irreparable, the patient needs a partial menisectomy to unlock the knee and prevent further damage
In a bucket handle meniscal tear, what causes the locked knee sign?
Central fragment displaces into the intercondylar notch, causing mechanical locking of the knee joint
Describe degenerative meniscal tears
Common, although many are asymptomatic; may represent the 1st stage of OA
Management of degenerative meniscal tears?
Inflammation from initial onset may settle and many people improve within 3 months
Surgery is less successful, esp. if there is evidence of existing OA on X-ray; arthrosopic menisectomy tends to be unsuccesful and is only for an unstable tear with mechanical symptoms, not for pain only
Steroid injections may help
Grading of knee ligament injuries?
Grade 1 (sprain) - some fibres torn but macroscopic structure is intact
Grade 2 (partial tear) - disruption of some fascicles
Grade 3 (complete tear)
Variation in ligament healing capabilities?
Some heal more than other and some stabilise over time:
• MCL tends to heal well, even if there is a complete tear, unless combo with ACL/PCL rupture; can use bracing, early motion and physiotherapy (surgery is rare) although pain takes several months to settle
Scenario of ACL rupture?
Usually, a sporting twist injury, accompanied by a POP
Within a few hours, the knee swells with a haemarthrosis, as the ACL contains a blood vessel
Management of ACL ruptures?
ACL reconstruction only, using:
• Autograft (with patellar tendon/hamstrings)
• Allograft (Achilles tendon)
• Synthetic graft
Also, ACL can be stuck to the PCL to give some stability, and physiotherapy can stabilise ACL deficient knees
What is the ACL rupture rule of thirds?
1/3rd of people compensate and are able to function well
1/3rd can avoid instability by stopping certain activities
1/3rd do not compensate and have frequent instability or cannot get back to high impact sport
NOTE: older patients are more likely to compensate or avoid high impact sports
Role of surgery in ACL rupture?
For rotatory instability that is not responding to physiotherapy; this allows rapid return to professional sport/high demand job
May be suitable for a adolescent/young adult that enjoys high impact sport
May also be used as part of a multi-ligament reconstruction
Disadvantages of ACL rupture surgery?
Does not treat pain or prevent arthritis
The surgery only stops instability so, if there is none, there is no need to do surgery
Complication of ACL reconstruction?
- 10% failure rate
- Infection
- Stiffness
- Graft vs donor site morbidiity
Complications of ACL ruptures?
Most patients have X-ray changes evident of OA, within 10 years
Describe LCL injuries
Uncommon and are due to varus and hyperextension; often occur in combo with PCL/ACL injury
It does not heal well and can cause varus and rotatory instability
Complications of LCL injury?
High incidence of common peroneal nerve palsy so it causes foot drop
Management of LCL injuries?
Complete rupture requires urgent repair within 2-3 weeks
If later, reconstruction (with hamstrings or other tendon)
Presentation of PCL rupture?
Usually occurs with a direct blow to the anterior tibia, e.g: dashboard/motorbike, OR a hyperextension injury
Causes popliteal knee pain and bruising
Management of PCL rupture?
Isolated PCL rupture (rare) do not require reconstruction
If there is instability (recurrent hyperextension or feeling unstable when going downstairs) OR if it is part of a multi-ligament knee injury, it usually requires reconstruction
Describe knee dislocation
Usually caused by a serious, high energy injury with a high incidence of complications, e.g:
• Popliteal artery injury (tear, intima tera and thrombosis)
• Nerve injury (common peroneal nerve
• Compartment syndrome
Treatment of knee dislocation?
Emergency reduction and checking of neurovasular status; if there are vascular concerns, require vascular surgery
Require temporary stabilisation of the knee and usually multi-ligament reconstruction
Describe patellar dislocation and occurrence
More common than knee dislocation and is usually due to a rapid turn or direct blow
Increased incidence in females and adolescents; risk factors include:
• Ligamentous laxity
• Valgus knee
• Torsional abnormalities
Consequences of patellar dislocation?
10% have recurrent dislocation
It may cause chondral or osteochondral injury
Management of patellar dislocation?
Some may benefit from surgical stabilisation
Describe how extensor mechanism ruptures can occur
Extensor mechanism consists of quadriceps muscle and tendon, the patella and tendon, and the tibial tubercle
Falling onto flexed knees with contraction of the quads
Risk factors for extensor mechanism rupture?
Previosu tendonitis
Steroids
Chronic renal failure
Ciprofloxacin
Signs of extensor mechanism rupture?
Unable to straight leg raise (SLR); if they can do this, EMR is unlikely
If they cannot SLR, check for a palpable gap
Management of extensor mechanism rupture?
Require surgical repair
Main mechanisms of injury for the presentations in this lecture?
MCL - valgus
ACL/meniscal injury - twisting
LCL - varus
PCL - dashboard/hyperextension
Meniscal tear - getting up from squatting
Most common ligament injuries?
MCL is most common, followed by ACL
Classic Hx of an ACL rupture?
Football twist injury \+ POP and haemarthrosis \+ Generalised pain (settles after a few days \+ Rotatory instability
Classic Hx of a meniscal tear?
Getting up from squatting and experiencing a sudden, sharp pain along the medial joint line \+ Effusion \+ Recurrent medial pain \+ Catching +/- locking
Difference between POP and CRACK?
POP - ligament rupture
CRACK - fracture
