Knee Flashcards
Medial Collateral Ligament Function
- resists valgus force
- resists knee extension
- resists extremes of axial rotation, especially knee external rotation.
Common MOI for MCL
- valgus producing force with foot planted
- severe hyperextension of the knee
Lateral Collateral Ligament Function
- resists varus
- resists knee extension
- resists extremes of axial rotation
Common MOI for LCL
- varus producing force with foot planted
- severe hyperextension of the knee
Posterior Capsule Function
- resists knee extension
- oblique popliteal ligament resists knee ER
- posterior lateral capsule resists varus
Common MOI for posterior capsule
-hyperextension OR combined hyperextension with knee ER of knee
ACL function
- resist extension
- resists extremes of varus, valgus, and axial rotation
Common MOI for ACL
- large valgus producing force with foot firmly planted
- large axial rotational torque applied to the knee with foot firmly planted
- any combo of valgus force with axial rotation, especially with strong quadricep contraction with the knee in full or near full extension
- severe hyperextension of the knee
Function of PCL
- resist knee flexion
- resists extremes of varus, valgus, and axial rotation
Common MOI for PCL
- falling on a fully flexed knee with ankle plantar flexed so tibia hits ground first.
- forceful posterior translation of the tibia
- large axial rotation or valgus-varus applied torque to the knee with foot firmly planted
- severe hyperextension of the knee causing a large gapping of posterior joint
ACL incidence of re-tear
- 8% tear ipsilatarel ACL
- 7% tear contralateral ACL
When do non-contact ACL injuries happen
- happen during deceleration and acceleration motions with excessive quadriceps contraction, and reduced hamstring contraction at or near full extension
- risk increases when combined with knee internal rotation, or excessive valgus load during weight bearing deceleration activities.
Common ways of PCL injury
- dashboard (posterior force to tibia) 38.5%
- fall on flexed knee with foot plantarflexed 24.6%
- sudden hyperextension of knee 11.9%
ACL incidence of re-tear
- 8% to ipsilateral ACL
- 7% to contralateral ACL
- Higher in pts <25 years of age
When do non contact ACL injuries happen
During deceleration and acceleration motions with excessive quadriceps contraction and reduced hamstring contraction at or near full extension.
Likelihood of returning to sport post ACLR
- 81% return to some level of sport
- 65% return to preinjury level of sport
- 55% return to competitive level of sport
Risk factors for developing ACL tear
- dry weather conditions and artificial turf
- female
- narrow intercondylar femoral notch
- lesser concavity depth of the medial tibial plateau
- Greater anterior/posterior tibiofemoral joint laxity
- prior ACLr
- familial predisposition
Diagnosis of ACL tear can be made with reasonable certainty with the following criteria…
- MOI consistent with a deceleration and acceleration motions with non contact valgus load at or near full extension. -
- hearing or feeling a “pop” at time of injury
- hemarthrosis 0-12 hours after injury
- hx of giving way
- (+) lachman test
- (+) pivot shift test
Diagnosis of PCL tear can be made with reasonable certainty with the following criteria…
- posterior directed forece on the proximal tibia, a fall on a flexed knee with plantarflexed foot, or a sudden violent hyperextension of the knee joint
- localized posterior knee pain with kneeling or deceleration
- (+) posterior drawer test at 90 degrees
- posterior sag of proximal tibia
Diagnosis of MCL tear can be made with reasonable certainty with the following criteria…
- trauma buy a force applied to the lateral knee or LE
- rotational trauma
- medial knee pain with valgus stress test
- increased separation between femur and tibia with valgus stress test
- TTP over MCL
Diagnosis of LCL tear can be made with reasonable certainty with the following criteria…
- varus trauma
- localized swelling over the LCL
- TTP over the LCL
- lateral knee pain with varus stress test
- increased separation between femur and tibia with varus stress test
Expected symmetry in single limb hop tests
- 76%-90% 6 months post ACLr
- 88%-95% 12 months post ACLr
- 92%-99% 24 months post ACLr
Single leg hop tests
- hop for distance
- crossover hop for distance
- 6 meter timed hop
Meniscus lesion statistics
- women have greater incidence than men
- lateral tears are more likely to occur in younger pts and medial tears are more likely in older pts.
- increased prevalence of meniscus tears with ACL tears
- > 45 y/o likely to have menisectomy, <35 years old likely to have meniscus repair
Methods of operation for articular cartilage damage
- arthroscopic lavage and debridement
- microfracture (used in younger patients)
- autologus chondrocyte implantation (ACI)
- osteochondral autograft transplantation (OAT)
Arthroscopic lavage and debridement
- typically for knee OA
- clean out joint space
Microfracture
- cartilage is cleaned up
- small microfractures made 3-4mm apart
- 75-80% of patient report significant pain relief
Autologus chondrocyte implantation
- surgeon harvests some articular cartilage then isolates the chondrocytes in the lab
- 6-8 weeks later chondrocytes are implanted over the articular cartilage defect
Osteochondral autograft transplantation
- small chunk of bone and damage cartilage removed
- new piece of bone and healthy cartilage is re-implanted, can be autograft or allograft
- self reported better outcomes in athletes compared to ACI and microfractures
Risk factors for articular cartilage damage
- athletes in cutting and pivoting sports are at increased risk
- women, older age, increased BMI, decreased physical activity, and delayed ACLr are risk factors for medial meniscus tears.
- women, older age, increased BMI, longer symptom duration, previous procedures and surgeries, and lower self reported knee function are associated with higher failure rates with articular cartilage repair procedures
Diagnosis of meniscus tear can be made with fair certainty with the following findings…
- twisting injury
- tearing sensation at time of injury
- delayed effusion (6-24 hours post injury)
- hx of “catching” or “locking”
- pain with forced hyperextension
- pain with maximum passive knee flexion
- pain or audible click with McMurray’s test
- joint line tenderness
Diagnosis of articular cartilage defect can be made with low level certainty with the following findings…
- acute trauma with hemarthrosis (0-2 hours) associated with osteochondral fx.
- insidious onset aggravated by repetitive impact
- intermittent pain and swelling
- hx of “catching” and “locking”
- joint line tenderness
Early intervention strategies for meniscus injury
- progressive AROM and PROM
Early to late rehab strategies for meniscus injury
- progressive weight bearing
- progressive return to sport
- supervised rehab
- ther-ex
- NMR
Early rehab strategies for articular cartilage damage
- progressive AROM and PROM
Early to late rehab strategies for articular cartilage damage
- progressive weight bearing (reach full weight bearing by 6-8 weeks)
- progressive return to activity (dependent on type of surgery)
- ther ex
- NMR
Functional limitations with patellofemoral pain
-pain with squatting, sports, stairs, prolonged sitting, and walking
Risk factors for patellofemoral pain
- poor knee extension strength
- decreased quad flexibility
- shorter reflex response time of VMO
- decreased vertical jump height
- higher than normal medial patellar mobility
- weakness in hip ABD’s, trunk extensors, and ankle plantar flexors in women
- decreased rate of time to peal rear foot eversion and greater rear foot eversion at initial heel contact during walking.
Psychological factors for patellofemoral pain
- mental health (anxiety and depression)
- cognitive factors (pain catastrophization)
- behavioral factors (fear of movement)
Who will have poorer outcomes with patellofemoral pain recovery?
- pain >4 months
- increased age
- higher baseline severity of pain
- lower patient function
Cluster tests for PFP
- presence of retropatellar or peripatellar pain
- reproduction of pain with squatting, stair climbing, prolonged sitting, or other function activities that load PFJ in a flexed position
- exclusion of all other conditions that may cause anterior knee pain, including tibiofemoral pathologies.
Overuse/overload without other impairment for anterior knee pain
- too much load magnitude, too much load frequency, and/or at too great a rate of increase
- those at risk for overuse include athletes and military population
- load magnitude: amount of PFJ loading resulting from physical activity
- load frequency: amount of repetition of an activity
Muscle performance deficits with regards to anterior knee pain
- hip strength deficits, especially weakness with hip ABD’s, extensors, and external rotators
Movement coordination deficits with regards to anterior knee pain
- increased hip ADD, hip IR, and knee abduction during dynamic activities can increase dynamic Q angle, knee ABD, and ER.
Mobility impairments
- lack of mobility of structures surrounding the knee can potentially increase compressive forces across PFJ
Differential dx’s for knee pain (medical)
- tumors
- dislocation
- septic arthritis
- arthrofibrosis
- DVT
- neurovascular compromise
- fracture
- slipped capital femoral epiphysis
Differential dx’s for knee pain (musculoskeletal)
- lumbar radiculopathy
- peripheral N entrapment
- hip/knee OA
- ligamentous injuries
- meniscal injuries
- articular cartilage injuries
- distal ITB syndrome
- quad/patellar tendonopathies
- plica syndrome
- patellar and tibial apophysitis
- patellar subluxation or instability
Differential dx for anterior knee pain
- PFP
- patellar tendonopathy
- patellar subluxation or dislocation
- tibial apophysitis
- patellar apophysitis
Patellar tendonopathy
- pain localized to inferior pole of patella
- TTP over patellar tendon
- aggravated by activities that require high rates of knee extensor loading, such as jumping or sprinting
Patellar instability
- apprehension with passively applied lateral patellar movement
Tibial and patellar apophysitis
- age and TTP over tibial tubercle and inferior pole of patella
Classification system for PFP
- overuse/overload without other impairments
- PFP with muscle performance deficits
- PFP with movement coordination deficits
- PFP with mobility impairments
Interventions for PFP
- exercise (open and closed chain)
- taping
- foot orthoses
Assessments and treatment used for overuse/overload PFP
- eccentric step down test
- reproduction of anterior knee pain
- taping (B level)
- activity modification/relative rest (level F)
Assessments and treatment used for movement coordination deficits
- dynamic valgus on lateral step down test
- frontal plane valgus during single leg squat
- gait and movement retraining (C level)
Assessments and treatment used for PFP with muscle performance deficits
- HipSIT (resisted clamshell mmt)
- isometric hip muscle strength testing
- thigh strength testing
- hip/gluteal muscle strengthening (A level)
- quadriceps strengthening (A level)
Assessments and treatment used for PFP with mobility impairments
- hypermobility in foot
- hypomobility in LE muscles and hip IR and ER ROM
- hypermobility: foot orthoses (A level), taping (B level)
- hypomobility: patellar retinaculum/soft tissue mobs (F level), muscle stretching (F level)
ACL biomechanics
- prevents hyperextension of the knee, anterior translation
- most commonly injured ligament ini the knee, usually non contact injury
- acts as secondary restraint against varus/valgus force
PCL biomechanics
- often injured with contact injury
- limits posterior translation of the tibia
MCL biomechanics
- primary restraint against valgus and lateral rotation forces
- most taut in full extension
LCL biomechanics
- primary varus restraint
- limits internal tibial rotation
- greatest strain on LCL occurs in full extension and tibial ER
- in an ACL deficient knee, it is a secondary restraint to anterior and internal rotation forces
- least often injured ligament in the knee
Muscles that provide anterior tibial shear
- quadriceps
- gastrocnemius
- Limit with ACL tears initially
Muscles that provide posterior tibial shear
- hamstrings (greater force as knee flexion increases)
- soleus (only when planted on the ground)
- Limit with PCL tears initially
Open vs close chained exercises
- Open chain: quads thought to put greater anterior shear forces on tibia (especially in full extension)
- most stress going through ACL with last 15 degrees of knee extension
Close chain: co-contraction of hamstring and quads is thought to provide more stability to the knee joint and less stress to ACL/PCL
Greatest strain through ACL with specific exercises
- isometric quad contraction at 15 degrees knee flexion
- squatting with sport cord
- active flexion-extension with 45N weight boot
- lachman’s test
- squatting
Least strain through ACL with specific exercises
- isometric quad contraction from 30-90 degrees
- simultaneous quad and hamstring contraction 60-90 degrees
PCL motor control
- agonists: popliteus mm helps limit posterior translation of the tibia. Quads reduce the strain on the PCL between 20-60 degrees.
- antagonists: gastrocnemius puts the most strain on the PCL when knee is flexed >40 degrees. Hamstring provides significant posterior shear.
Exercise/management of meniscus tear
- limit excessive end range knee flexion
- minimize tibial rotation
- regular force on the meniscus is important for healing
- 6 week return to activity program, minimum
Biomechanics of ITB
- ITB is a passive lateral stabilizer pf the knee though has very little movement
- knee flexed: ITB is posterior to lateral femoral condyle
- knee extended: ITB is anterior to lateral femoral condyle
- has a minor attachment to the patella
Lateral knee pain etiology
- most common running injury 1.6-12%
- comprises 15% of all knee injuries in cyclists
- thought to be caused by excessive load on the band over the knee
- ITB alternates from flexor to extensor at about 20 degrees of flexion.
Management of lateral knee pain
- treat inflammation during acute phase
- stretching ITB and related structures
- strengthening of hip ABDs
- manual therapy to soft tissue structures
- improve motor control
- rest and activity modification
Primary purpose of meniscus
- load transmission at the knee
- shock absorption
- joint stability
- joint nutrition
- joint lubrication
- joint proprioception
- absorbs 50-70% of compressive forces in the knee
- only the outer 10-30% is vascularized
Lateral meniscus
- 4/5ths of a circle
- larger than medial meniscus
- more mobile than medial meniscus (10 mm movement)
- muscle attachments: popliteus, which aides in stability
- less commonly injured compared to medial meniscus
Medial meniscus
- C-shaped
- smaller than lateral meniscus
- less mobile (2 mm of movement)
- muscle attachment: semimembranosus, which aides in stability
- Broader posterior than anterior
- Absorbs greater and more frequent forces than lateral side
- More attachments to the joint capsule, which limits translation and movement
Ottawa knee rule
- age 55 or older
- isolated tenderness of the patella
- tenderness of the head of the fibula
- cannot flex to 90 degrees
- unable to weight bear both immediately and in the ER
- used only for injuries <7 days
Why do ACLr?
- restore knee stability
- prevent meniscal damage
- protect articular cartilage
- avoid degenerative changes
Anterior-medial bundle of ACL
most taught in flexion
Posterior-lateral bundle of ACL
most taught in extension
