Knee Flashcards
With excessive genu varum, what compartment (medial or lateral) will have increased loading?
Medial compartment
With excessive genu valgum, that compartment (medial or lateral) will have increased loading?
Lateral compartment
What are the anterior knee joint capsule reinforcements?
- Medial & Lateral patellar retinacular fibers
- Quadriceps tendon
- Patellar tendon
The tendons of what muscles insert at the pes anserine? What nerve are they each innervated by?
S artorius F emoral N
G racilis O bturator N
T (semiTendinosis) T ibial N
What are the lateral knee joint capsule reinforcements?
- LCL (not a part of capsule)
- Lateral patellar retinaculum
- IT band
- Lateral coronary ligaments (small fibers that run vertically from lat meniscus –> tibia)
- Biceps femoris
- Popliteus
What bony landmark does the IT band and tibialis anterior insert?
Gerdy’s tubercle (lateral condyle of tibia)
What knee joint capsule reinforcements make up the posterolateral complex (PLC)?
- LCL
- Arcuate lig
- Popliteofibular lig (head of fibular –> tendon of popliteus)
- Popliteus tendon
What are the posterior knee joint capsule reinforcements?
- Oblique popliteal lig (lat femoral condyle –> medial tibia)
- Arcuate popliteal lig (fibular head –> lat femoral condyle)
- Gastroc
- HS
- Popliteus
What are the medial knee joint capsule reinforcements?
- Medial patellar retinaculum
- MCL (part of capsule - NOT outside like LCL)
- Medial coronary ligs (medial meniscus –> tibia)
- Pes anserine group (Sartorius, gracilis, semitendinosus
T of F: the cruciate ligaments are inside the fibrous capsule but outside the synovial capsule
True
What are the names of the 4 synovial capsule outpouching (bursae) of the knee?
- Suprapatellar
- Popliteal
- Gastrocnemius (lat and med)
- Semimembranosus
What are 3 bursae of the knee that are NOT connected to the synovial capsule?
- Prepatellar bursa (in front of knee)
- Deep infrapatellar (behind patellar tendon)
- Pes anserine
When these are filled with fluid, its called extraarticular swelling since it’s outside the joint.
What are 2 purposes of fat pads of the knee (“Hoffa’s fat pad”)
- Protection
- Lubrication
What are plicae of the knee?
Synovial folds
What are the 4 specific plicae of the knee?
- Suprapatellar
- Mediopatellar
- Infrapatellar (ligamentum mucosum)
- Lateral
What is the clinical implication/”so what” of plicae?
They can become inflamed/fibrotic and be painful (plicae syndrome)
Which of the 4 plicae of the knee is the most problematic?
A. suprapatellar
B. mediopatellar
C. infrapatellar
D. lateral
B. Mediopatellar plica
What kind of joint is the tibiofemoral joint?
Bicondyloid –>
- med femoral condyle & med tibial plateau
- lat femoral condyle & lat tibial plateau
condyloid jts = 2 degrees of freedom –> for knee: sagittal plane - flex/ext, transverse plane - med/lat rot
What are menisci composed of?
Fibrocartilage
What purpose/functions do menisci serve?
-Convert relatively flat tibial plateaus to concave sockets for femoral condyles –> guides knee motion & contributes to jt stability
-Absorb shock
-Distribute force
-Lubrication of tib-fem articulation
How are menisci anchored to the tibia?
- Ant/post meniscal horns
- coronary ligs (meniscotibial)
Describe the vascularity of menisci
Outer 1/3: LOTS
Middle 1/3: Some
Inner 1/3: Little
Describe the innervation of menisci
Aneural except at the meniscal horns
What are the clinical implications of meniscal vascularity and innervation?
Where the tear occurs matters - does it have the vascular supply to heal? Or is surgery required? Age also matters!
Compare and contrast the medial and lateral menisci in shape, attachments, and mobility
Medial:
- Shape: C
- Attachments: MCL, Semimembranosus, quadriceps
- Mobility: less
Lateral:
- Shape: O
- Attachments: popliteus, semimembranosus, quadriceps
- Mobility: greater
Which menisci is more commonly injured?
Medial meniscus is more commonly injured.
Why does the lateral meniscus have greater mobility than the medial?
-LCL doesn’t attach to lateral meniscus but the MCL does attach to medial meniscus
-Coronary ligs on lateral side are less dense then medial side
Removing an entire meniscus increases peak contact pressure by ___%
A. 50%
B. 100%
C. 150%
D. 230%
D. 230%
What is the MOI for meniscus?
ROTATION of femur over FLEXED knee in WBing
What is the primary function of the MCL?
Resist external valgus force
Based off of when the MCL is taut versus relatively slack, what motion would cause increased pain? Flex or ext?
Extension
What is the primary function of the LCL?
Resist varus stress/force
What is the primary purpose of the cruciate ligs: ACL and PCL?
Control of knee arthrokinematics
T or F: Mechanoreceptors are present in ACL and PCL
True.
Where does the ACL attach?
Anterior tibial spine > medial aspect of lateral femoral condyle
T or F: the ACL has 2 portions, one that is tight in flex and one tight in ext
True.
Posterolateral: tightest in ext
Anteromedial: tightest in flex
In what ways does the ACL become taught? aka how can you tear your ACL?
- Ant translation of tibia on femur
- Post translation of femur on tibia
- End range ext
- Extremes of varus, valgus, and tibiofemoral rot
Assign the Quads and Hamstrings as either ACL agonist or antagonist.
Quads: Antagonist (quad contraction –> ant glide of tibia –> tensions ACL)
HS: Agonist (HS contraction –> post glide of tibia –> ACL on slack)
What are the MOI for ACL?
Usu NON-contact (or limited):
- Rot of trunk over planted foot
- Deceleration w/ knee hyperext
Contact:
- Varus/valgus force
- Hyperext force
Where does the PCL attach?
post tibia below plateau to lat aspect of med femoral condyle
Is the ACL or PCL injured more frequently?
ACL
T or F: the PCL has 2 portions, one that is tight in flex, the other in ext
True.
Anterolateral: more taut in flex
Posteromedial: more taut in ext
PCL resists/becomes taut w/:
- Ant translation of femur on tibia
- Post translation of tibia on femur
- End range FLEX
- Extremes of varus, valgus, and rot
Assign the Quads and HS as either PCL agonist or antagonist
Quads: PCL agonists
HS: PCL antagonists
What ligament would you be concerned about for a MOI of falling onto a flexed knee w/ the foot plantar flexed (applies post force to prox tibia)?
PCL
Name to extensors of the knee
- Quadriceps (rec rem, vasti group)
- TFL: weak (20 flex - 0 full ext)
- Gastroc: in closed chain ONLY (mid-late stance in gait)
Name the primary knee flexors
- Semitendinosis
- Semimembranosus
- Biceps femoris (short & long head)
Name knee flexor synergists (not the main knee flexors)
- TFL: weak (>20 deg flex)
- Popliteus
- Gastroc: in OKC
- Sartorius
- Gracilis
Suppose you have an injury to the tibial nerve, how would that affect movement at the knee?
Decreased knee flexion strength (since the 3 primary knee flexors are innerv by the tibial n)
Suppose you have any injury to the femoral nerve, how would that affect movement at the knee?
Decreased knee ext strength (since the quads are innervated by the femoral n and they ext the knee)
How would knee flexor strength be affected by injury to:
- Tibial div of sciatic n?
- Fibular div of sciatic n?
- Femoral n?
- Obturator n?
What are the functional sagittal plane motion requirements for:
- Normal gait
- Stairs
- Sit to stand
- Normal gait: Full ext –> 60-70 flex
- Stairs: Full ext –> 80-85 flex
- Sit to stand: 100-115 flex
At what degree of flex is voluntary axial rotation motion the greatest?
90 deg flex
What is the “screw home” mech of the tibiofemoral joint?
Mechanically involuntary coupled rotation that occurs in final 15 deg of ext –> “locks” knee in full ext
Caused by:
- Asymmetry of femoral articular surfaces
- Tension in ACL and PCL
- Lateral “pull” of quads
In OKC, how does the tibia rotate on the femur during the screw home mech/automatic rotation into ext?
Tibia ext/lat rotates on femur
In CKC, how does the FEMUR rotate on the TIBIA during the screw home mech/automatic rotation into ext?
Femur int/med rotates on tibia
How does popliteus function to “unlock” the knee from a fully extended/locked position? Consider OKC and CKC.
OKC: int/med rot tibia on femur
CKC: ext/lat rot of femur on tibia
What is the closed packed position of the knee?
Full ext
Ext/lat rot of tibia on femur (or med/int rot of femur on tibia in CKC)
What is the loose-packed position of the knee?
25-30 deg flex
