Week 5 - Knee Flashcards
Anatomy of ACL and discuss biomechanics + MOI of injury
2 main strains - AMB (anteriomedial band) and PLB (posteriolateral band)
Posterior medial femoral condyle to anterior intercondyloid eminence of tibia in intercondylar notch
Resists anterior tibial displacement on femur and rotational loads
Secondarily prevents hyperextension, varus and valgus stresses
Most injuries occur in closed kinetic chain (where distal aspect of extremity is fixed)
Least stress on ACL between 30-60 degree of flexion
Anteromedial bundle tight in flexion (and extension)
Posterior lateral bundle tight only in extension
(Markatos et al 2013, Levangie & Norkin 2011)
Therefore:
Most common mechanisms are when values force with twisting motion or hypertension knee
Non-Contact (Most common):
* Most common
* Due to sudden deceleration
* Sudden landing, cutting, or pivoting
Contact:
* CKC with foot ER w/ valgus stress
* Hyperextension
* direct hit on the posterior tibia
Signs/symptoms of ACL injury incl examination
Patient will c/o “buckling” or “giving away”, typically will hear and/or feel a “pop”.
Immediate swelling/hemarthrosis/effusion
Reduction of extension and signs of ACL laxity. Following signs may be positive:
- Brush Stroke Bulge
- Lachman test
- Anterior drawer test
- Pivot shift test
Recurrent episodes of instability increases risk of accelerated OA
Surgery in ACL?
Depends on circumstances eg sport, level of competition, partial/full tear
Repair indicated if:
Associated meniscal or MCL damage
High level athletes
Lower level athletes who wish to pursue sports which involve pivoting
Children/adolescents
Knee remains unstable following rehab
Occupational factors
50% return to competitive sport after ACL reconstruction, majority RTS in professional football
60% of non-professional athetes RTS,
1 year RTS after surgery
How do manage ACL tear in paediatrics?
o Increasd change of returning to pre-injured level of function after surgery, some evidence that early ACL reconstruction is more beneficial than delayed, with less incidence of instability and fewer meniscal tears.
o But did non op patients return to sport too soon vs surgical management who would have waited 9/12 to return? (Dunn et al 2016)
ACL is reconstruction merited in over 60?
o Evidence to suggest ACL reconstruction sensible in non arthrtic knee, but not in an arthritic knee
o Again limited evidence (small sample size, not many studies). (Toanen et al 2017)
Early stage rehab for ACL
- Non stressful load applied through injured structure - helps as a muscle pump to encourage flow around the knee
- Early dynamic stabilization/proprioception ( narrow center of gravity, adjust center of gravity, close eyes)
- Early activation of quads/hammys/glutes/gastroc
- Ensure return of kinetic chain ROM at hip and ankle
- Avoid open chain for 6/52
- Management of swelling
Mid stage rehab ACL knee
- Kinetic chain rehab
- Regain full AROM
- Maintain flexibility
- Acceptance of load through the joint
- Progressively increase the load
- Introduce dynamic component and increase CV (pool, aqua jog, xtrainer)
End stage rehab knee
- Gym based strength
- High level proprioception
- Graduated, phased, return to running
- Work towards full functional activities
- If dynamic sport then must include gradual introduction of ballistic and explosive activities/plyometrics
- Graduated RTS
RTS after and ACL reconstruction
- Time!
- Address any psychological factors
- Full strength (isokinetic – hams/quad ratio, L vs R, through range, leg press, comparison to pre injury levels)
- ROM
- High level of neuromuscular control
- Performance & skill execution
- Optimal loading – load progression is key
- Research evidence on RTS is scarce
(Kyritsis et al 2016, Ardern et al 2016)
RTS after and ACL reconstruction
- Time!
- Address any psychological factors
- Full strength (isokinetic – hams/quad ratio, L vs R, through range, leg press, comparison to pre injury levels)
- ROM
- High level of neuromuscular control
- Performance & skill execution
- Optimal loading – load progression is key
- Research evidence on RTS is scarce
(Kyritsis et al 2016, Ardern et al 2016)
Meniscus functions
Primary – load distribution, joint stability, shock absorption
Secondary – joint lubrication, articular cartilage nutrition, proprioceptive feedback
MOI Meniscal injury
Trauma
* Compression
* Rotational Force
* Valgus Force
* Usually Combination of Forces
Degenerative Changes
* Greater than 30 years old
* No PMHX required
* Often due to MOI that “seemed harmless” at time
* Noyes (2002) states 60% of meniscal injuries associated with ACL injury
(problem knee = ACL, MCL, medial meniscus)
Examination meniscus injury
“Duck walk” - screwing in to medial and lateral compartment (pain with swuatting). Buckling/giving way. Medial/lateral joint pain. Effusion (Shelbourne et al 1995, Bernstein 2000)
If able to fully squat, no meniscal injury
* Rule out other structures
* Joint line palpation
* Apley’s test
* McMurrays test
* Thessaly test
Medial collateral ligament primary role
Primary role is to prevent against a valgus force and external rotation of the tibia
MOI/examination of MCL
Most frequently injured ligament in the knee
Typically due to valgus forces in CKC position. Foot in neutral or externally rotated position eg football, rugby, skiing.
MOI = Any forceful movement of the lower leg outward at the knee or a hard blow to the outside of the lower thigh which causes the knee to buckle
Usually no joint effusion unless deep portion affected since primarily located outside the joint capsule (not contained within the joint)
Valgus stress test
Role of LCL
Primary role is to protect from varus forces and external rotation of the tibia, assists in 2° restraint for anterior and posterior tibial translation
Throughout Range of motion:
* taut during extension
* loose during flexion (especially after 30° of flexion)
MOI/examination LCL
Typically due to varus forces, especially in CKC position with leg adducted and tibia internally rotated
Usually during contact sports
Typically has limited joint effusion since it is located outside of the joint capsule
(Brunkner & Kahn 2012)
Varus stress test
Posterolateral complex injury can produce significant impairment (LCL, arcuate ligament, lateral head gastric, biceps femurs tendon and musculotendinous junction of popliteus muscle)
Can be repaired but typically done in association with surgery for the other damaged tissues
Functions of PCL
Functions:
Primary stabilizer of the knee against posterior movement of the tibia on the femur
Prevents flexion, extension, and hyperextension
(Levangie & Norkin 2011)
MOI/examination of PCL
Typically RTA and not sport (due to hyperextension, hyperflexion or tibia being forced posteriorly on femur). Could also occur falling on bent knee/hyperextension of knee
Isolated PCL unusual
Avulsion injuries
Mid-substance tears
Examination:
Posterior draw test +ve test indicates PCL, arcuate complex, possible ?ACL
Rubenstein, et al 1994 found posterior drawer test 90% sensitive for PCL injury (versus 58% for Quadriceps Active Test & 26% for Reverse Pivot Shift Test). Clinical exam on whole was 96% effective in detecting PCL dysfunction
Usually minimal swelling
Posterior sag test
Describe patellar compression and PFJ loading
Patellar compression
* OKC greatest at end range (final 30 degrees)
* increases in CKC after 30 degrees of flexion
(Levangie & Norkin 2011)
PFJ loading varies during OKC and CKC activities
PFJ laoding increases with increased flexion in CKC, and extension in OKC
Squatting is 7x body weight
(Levangie & Norkin 2011)
Causes of patellar malt racking:
Tirghtness of passive restrains (eg ITB), weakness of active restraints (VMO), weakness of glues leading to increase internal rotation at hips, muscle tightness of hamstrings and quads
Signs and symptoms PFJ
- Poorly localized pain
- Little to no swelling
- Point tenderness under lateral patella
- Insidious onset
- (Earl & Hock 2011)
–> Clarkes test
What is typically injured with medial collateral?
Closely associated with medial meniscus, so any forceful rotational element in addition to values strain can rupture MCL, medial meniscus and ACL (O’Donoghue’s Triad)
Why are women more likely to suffer from an ACL injury?
Smaller intercondylar notch and ACL
Lower limb mechanics
Hormonal variations
Joint laxity
Most common ACL involve harvesting:
Semitendinosus and gracilis tendons
Middle third of patellar tendon
Management PCL tear
Typically predominantly quad strengthening rehab programme. Surgery if posterolateral complex damage. These tears are associated with osteoarthritis.
Whats the Q angle
Angle at the junction between two lines drawn from the anterior superior iliac spine to the middle of the patella and a line drawn to the same point from the tibial tubercle
