Acute Knee Injuries Flashcards
Where does most of the weight bearing in the knee happen?
Medial meniscus/compartment
How is the medial femoral condyle different to the lateral?
Narrower and longer
Where do the cruciate ligaments sit?
In the intercondylar notch
- ACL: Lat/post - med/ant
- PCL: Med/post - lat/ant
What is the anatomy of the meniscus?
- Bi-concave
- C-shaped discs of fibrocartilage
- Viscoelastic material
- 75% water
How does the blood supply differ within the meniscus?
Outer 1/3 vascular, better chance of healing
What are the functions of the meniscus?
- Load sharing/transmission (Increase joint’s weight bearing area)
- Improve joint lubrication
- Shock absorption
- Articular cartilage nutrition
- Stabilise the joint, act as secondary restraints
- Maintain joint congruence by guiding femoral condyles
What are some of the different types of meniscus tears?
- Longitudinal
- Degenerative
- Flap
- Radial
- Bucket handle
- Horizontal cleavage
What type of imaging is used to view the meniscus?
MRI
What are the common mechanisms of injury for acute meniscus injuries?
- Impact blow, deep flexion, rotation insult
- Part of other injuries, e.g. ACL
- Rate of swelling into joint slow from torn meniscus
- May or may not have clicking, locking & giving way
What are the common mechanisms of injury for chronic meniscus injuries?
- Slow onset, no particular event but may be aggravated by an event
- Frequently occupation specific, e.g. long time in flexion
- Chronic knee effusion, small amounts of swelling, slow onset (puffy around joint line)
How does the movement of the femoral condyles and menisci differ in flexion between medial and lateral?
- Medial: Minimal translation of condyle, very stable (increased risk of injury)
- Lateral: Condyle slips off the back of the tibial plateau, meniscus requires lots of mobility to allow this
What are the support, protect, maintain principles for treating meniscus?
- Treat symptomatically, especially joint effusion
- Limit aggravating flexion in full WB
- If locked knee, requires urgent arthroscopy
What are the ‘regain’ treatments for meniscus?
- ROM: Treat/maintain muscle & capsular flexibility, maintain extension, gradually increase flexion ROM
- Strength: As required
- Control: Protect pint by teaching dynamic motor control/stability
- Function: Functional re-training, monitor outcomes 4-6 weeks, surgical options if not resolving
When do ACL injuries commonly occur?
- In sports involving pivoting & sudden deceleration (e.g. planting foot & twisting, usually non-contact)
- Higher incidence in females (2x) competing at similar level
- Isolation or in combination with MCL, medial meniscus or articular cartilage lesions
Why is there a higher incidence of ACL injuries in females?
- Anatomical: Wider pelvis & Q angle, narrow intercondylar notch, narrow ACL
- Hormonal: Increased general joint laxity
- Neuromuscular: Less quads/hamstring strength, different muscle recruitment pattern, landing techniques
- Shoe: surface interface (more common on hard surfaces)
What are the contact and non-contact mechanisms of ACL injuries?
Contact: - Valgus stress to outer aspect of joint - Posterior force while foot is fixed Non-contact: - Landing from a jump in rotated position - Pivoting - Sudden deceleration
What happens in the muscles/joint during a non-contact ACL injury?
Major quadriceps contraction force pulling the tibia anteriorly
What are some of the other injuries that can be associated with ACL injuries?
- Osteochondral lesion
- Bony oedema
- Meniscal injury
How is ACL avulsion treatment different to ACL tears?
- Tears: Let it settle down before repairing
- Avulsion: Repair as quickly as possible
What is a Segond fracture?
- Avulsion fracture of lateral tibial plateau
- Sign of ACL injury
What is the aim of surgical treatment for ACL injuries?
- Replace torn ACL with graft that reproduces normal kinetic function of the ligament
- Most commonly performed arthroscopically
What are some of the grafts used for ACL surgery?
- Bone-patellar tendon-bone
- Hamstring (semitendinosus +/- gracilis)
- Allografts (cadaver tissues): less frequent
What is a BPTB graft associated with?
Higher incidence of knee pain & pain on kneeling
What are one of the limitations of hamstring grafts?
End of range flexion weakness
What is a LARS graft?
- Ligament augmentation & reconstruction system
- Artificial ligament made from polyester
- Associated with faster recover
When can ACLR patients expect to return to some level of activity?
100% by 2 years, but significantly dropping off by 5 years
What amount of ACL laxity post repair is associated with poor outcomes?
Laxity > 10mm
What are the support, protect, maintain principles for treating ACLR?
- Treat symptomatically, especially joint effusion
- No open chain extension
What are the ‘regain’ treatments for ACLR?
- ROM: Esp. regain full extension early
- Control: Protect joint by teaching dynamic motor control/stability (cocontraction)
- Strength: As required (with cocontraction)
- Function: Re-training
What are the characteristics of a PCL injury?
- Less common, not as debilitating
- Hyperextension, dashboard or fall onto flexed knee
- Combines with P-L corner
- Not commonly reconstructed
How can the positioning of the tibia change with a PCL injury?
- Sags back, so posterior aspect doesn’t align with posterior aspect of condyles
- Noticeable in crook lying
- Can be mistaken as ACL injury (large anterior drawer)
What are the support, protect, maintain principles for treating PCL?
- Treat symptomatically, especially joint effusion
- May not require surgery
What are the ‘regain’ treatments for PCL?
- ROM
- Control: Protect joint by teaching dynamic motor control/stability (cocontraction)
- Strength: As required (with cocontraction)
- Function: Re-training
What is the mechanism of MCL injuries?
- Valgus force in partial flexion (to outside of knee)
- E.g. downhill skiing, contact sports
Why is the MCL tested at 0 and 30 degrees?
- Has connections with meniscus & deep layers of joint capsule (tested at 0 degrees)
- If laxity at 0 degrees, indicates more issues
Why does the MCL heal so well?
High levels of fibroblasts
What is a complication of MCL injuries?
Pellegrini-Steida lesion: Curvilinear calcification at site of previous MCL injury
What are the support, protect, maintain principles for treating MCL?
- Brace to minimise valgus
- Can mobilise fl/ex after 1/52 - limited ROM brace
- Usually good healer (4-6 weeks)
What are the ‘regain’ treatments for MCL?
- ROM: Heel slides, to bike, to function
- Control: Depends on lig healing; dynamic stability training, proprioception as required
- Strength: As required
- Function: Re-training
What is the mechanism of an LCL injury?
Varus force, rarely isolated (think P-L corner)
How is the treatment for LCL different from MCL?
- Make sure P-L corner is intact
- If not, spend more time on education, control, stability & outcome modification - likely to be loose for a long time
What commonly occurs in a patella dislocation?
- Takes of condyle fragments
- Results in osteochondral lesion
- Commonly becomes recurrent
What are the support, protect, maintain principles for treating patella dislocation?
- Brace in extension straight away, but with active isometric quads
- Can mobilise fl/ex when ligament test is satisfactory - limited ROM
What are the ‘regain’ treatments for patella dislocation?
Same as MCL & LCL, but focus on VMO control
Where does the patellofemoral joint obtain stability from?
- Medial & lateral retinaculum
- Large extensor mechanism tendons (quads & patellar)
What do the ACL & PCL prevent?
ACL: Prevents forward movement of the tibia & rotation of the tibia under the femur
PCL: Prevents femur from sliding forward off tibial plateau (e.g. running down stairs)
What is the mechanism of a patellar tendon rupture?
Sudden, severe eccentric quads contraction, e.g. stumbling, powerful take-off
What are the clinical signs of patellar tendon rupture?
- Sudden onset of pain, tearing sensation, undoable to stand
- Loss of fullness at anterior knee
- Patella retracted proximally
- Ext not possible from straight leg position
What is the treatment for a patellar & quads tendon ruptures?
- Surgical repair
- 6-9 months rehabilitation
What is the mechanism of a quads tendon rupture?
- Less common than patellar
- Non-contact, landing from jump/changing direction suddenly, falls
What are the clinical signs of quads tendon rupture?
- Unable to contract extensors
- Defect above patella
What is the mechanism of burial hematoma?
Fall onto knee
What does the posterolateral corner/complex consist of?
- Arcuate complex
- Biceps femoris tendon
- Popliteus tendon – helps to unlock knee
- Posterior capsule of tib fem joint
- LCL
- Lateral head of gastroc
Why is injury to the P/L corner so complex?
- Creates a lot of instability
- Anatomy is very layered & complex so most surgeons don’t want to operate on it
What is the function of the coronary ligaments of the knee?
- Hold the menisci down against the tibial plateau
- Esp medial meniscus - very stably bound
What ligaments bind the menisci to each other?
- Ligament of Wrisberg (posterior meniscofemoral)
- Ligament of Humphrey (anterior meniscofemoral)
