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Knee Joint
| Question | Answer |
|---|---|
| How many bones make up the knee joint? | 3 Femur, patella, tibia |
| How many degrees of freedom are in the knee joint? | 2 |
| What are teh articulating surfaces? | Medial tibio-femoral, Lateral tibio-femoral, patella-femoral |
| What is the function of the knee | Withstanding large forces, providing great stability, and enabling a large ROM |
| Mobility in the knee is given primarily by what structure? | Knee bony structure → shape of articular surface |
| Stability is provided by what structure in the knee? | Soft tissues: ligaments, muscles, and cartilage |
| How does the mobility and stability of the knee compare to the hip? | They are opposite. |
| Where are the femoral condyles separated? | Anteriorly - intercondylar notch |
| Why does the popliteus muscle add complexity to the joint capsule? | Origin is inside the joint Pierces the capsule to attach on the lateral femoral condyle |
| Why does the semimembranosus add complexity to the joint capsule? | Forms part of oblique popliteal ligament and gives off fibers to MCL, as well as its bony large attachment |
| Is the arcuate ligament an example of an intrinsic or extrinsic ligament? | Intrinsic, over popliteal muscle |
| What ligaments are responsibility for the trasnverse stability of knee during extension? | Collateral ligaments |
| Where does the medial collateral ligament run from? | Medial femoral condyle to tibia, posterior to pes anserinus tendon Runs inferiorly and anteriorly |
| Where does the lateral collateral ligament run from? | Lateral condyle to head of fibula |
| What are the collateral ligaments like during extension and flexion? | Taut - extension Slackened - flexion |
| Which ligaments are contained within the intercondylar notch and fossa? | Cruciate ligaments |
| What are the ACL attachments? | Anterior intercondylar area of tibia to lateral condyle of femur Runs superiorly, posteriorly, and laterally |
| What are the PCL attachments | Posterior intercondylar area of tibia to medial condyle of femur |
| What is the function of the cruciate ligaments? | Stabilize knee in antero-posterior direction Allows joint to work as a hinge while keeping the articular surface in contact |
| What does the acronym APEX stand for? | ACL attaches to anterior intercondylar area (tibia) runs posteriorly and attaches to external femoral condyle |
| What does the acronym PAIN stand for? | PCL attaches to posterior intercondylar area (tibia) and runs anteriorly and attaches to internal femoral condyle |
| What is the function of ACL? | Prevents anterior displace of tibia on femur |
| What is the function of PCL? | Prevents posterior displacement of tibia on femur |
| How is the lack of congruency in the articular surfaces in the knee joint corrected? | Menisci |
| What is the menisci? | Semi-lunar fibrocartilages. Incomplete rings in the intercondylar tubercles of tibia. Have anterior and posterior horns |
| How do two menisci compare to each other? | Medial - more C shapes. Horns don't come together. Lateral - more O shaped. Horns come closer together |
| What links the two anterior horns of the menisci? | Transverse ligament of the knee |
| What forms the meniscopatellar ligament? | Fibrous bands running from lateral edges of the patella to lateral borders of each meniscus |
| Which collateral ligament is attached to the medial meniscus? | MCL |
| Why isn't the LCL directly attached to the lateral meniscus? | Tendon of popliteus - sends fibrous expansion to posterior border of lateral meniscus |
| What muscle sends a fibrous expansion to posterior edge of the medial meniscus? | Semimembranosus |
| What forms the meniscofemoral ligament? | PCL fibers in the posterior horn of lateral meniscus |
| What is the attachment for both meniscus? | Tibial condyle |
| Why is the medial meniscus more fixed than the lateral meniscus? | Attaches to one more structure |
| What is the implication of medial meniscus being more fixed? | More prone to damage |
| What is the terrible triad? | ACL, MCL, and medial meniscus |
| What is the geometric center? | Joint line passing horizontally through femoral condyles |
| What is the instant center of rotation of Reuleaux? | Axis coinciding with center of cruciate ligaments in sagittal plane - for flexion/extension |
| What would happen if the femur rolled on tibia without sliding? | After a certain measure of flexion, femoral condyle would tip over behind tibial condyle |
| What is the assumption we can make of the knee based on the fact that the circumference of the femur is greater than the tibia? | There is no possibility of simple rolling of femur |
| What would happen if the femur slides without rolling on knee joint? | Femur on posterior border of tibia condyle would prevent further flexion |
| Where does axial rotation occur in? | Transverse plane when knee is flexed |
| What happens to the knee in extension for axial rotation? | Collateral ligaments are tense and contribute to joint stability so no movement |
| Describe the movement of the condyles in axial rotation | Lateral condyle rotates around the medial condyle |
| Why does the lateral condyle rotate around the medial condyle? | Axis for rotation is longitudinal and located medial to intercondylar eminence of tibia |
| What limits the motion in axial rotation? | Capsular and ligamentous structure: collateral, cruciate, oblique popliteal, retinacula, and IT band |
| What is the Screw-Home Mechanism? | Type of automatic axial rotation linked to movements of flexion and extention |
| Can axial rotation take place when the knee is extended? | No, only in flexion |
| Describe the movement of the lateral femoral condyle during lateral rotation of tibia on femur | Lateral femoral condyle moves anteriorly over and while lateral tibial condyle moves posteriorly |
| Describe the movement of the medial femoral condyle during lateral rotation of tibia on femur | Medial femoral condyle moves posteriorly over and while medial tibial condyle moves anteriorly |
| Describe the movement of lateral femoral condyle during medial rotation of tibia on femur | Lateral femoral condyle moves posteriorly over and while lateral tibial condyle moves anteriorly |
| Describe the movement of medial femoral condyle during medial rotation of tibia on femur | Medial femoral condyle moves anteriorly over and while medial tibia condyle moves posteriorly |
| Which condyle moves more during axial rotation of the knee? | Lateral condyle moves 2X more than medial |
| What direction does the tibial condyle move during extension? | Anteriorly |
| What direction does the tibial condyle move during flexion? | Posteriorly |
| During rotation, meniscus follows movement of which condyle? | Femoral |
| During flexion/extension, meniscus follows movement of which condyle? | Tibial |
| What role does vastus medialis play in knee joint extension? | Prevents displacement of patella because it moves laterally during extension |
| Which muscle stabilizes the patella? | Quads |
| How is the Q-angle formed? | Between longitudinal axis of femur (tendon of quads) and patellar ligament |
| What is the Q-angle in med and women? | Men - 10. Women - 15 |
| What is the implication of genu valgum? | Patellofemoral joint abnormalities: chondromalacia patella and patellofemoral tracking problems |
| What stabilizes the stresses applied during walking and running of the knee, transversly? | Collateral ligaments, sartorius, semitendinosus, and gracilis |
| What is a valgus stress? | MCL torn |
| What prevents further flexion of knee? | Quads (maintains erect posture) |
| What stabilizes the knee anteriorly and posteriorly? | Joint capsules, arcuate ligaments, OPL, Semimembranosus, LCL, MCL, PCL, pes anserine, biceps femoris, gastrocnemius |
| Why is axial rotation impossible in extension? | Tension of cruciate and collateral ligaments |
| Describe the tension of cruciate and collateral ligaments during lateral rotation? | Slack cruciate. Tight collateral. |
| Describe the tension of cruciate and collateral ligaments during medial rotation. | Tight cruciate. Slack collateral. |
| What are the extensor muscles of the knee? | Vastus intermedius/lateralis/medialis, Rectus femoris |
| What are the flexor muscles of the knee? | Hamstrings, biceps femoris, gracilis, sartorius, gastrocnemius |
| What are the medial rotators of the knee? | Semitendinosus, semimembranosus, popliteus, gracilis, sartorius |
| What are the lateral rotators of the knee? | Biceps femoris, TFL, glute max |
| Which muscle produces highest torque for extension of the leg when the hip is in an extended position? | Rectus femoris |
| What are the prime movers of flexion? | Biceps femoris, semitendinosus, semimembranosus |
| What are the prime movers of extension? | Rectus femoris, vastus intermedius/medialis/lateralis |
| What is the prime mover of lateral rotation? | Biceps femoris |
| What are the prime movers of medial rotation? | Semimembranosus, semitendinosus, popliteus |
| What are synergists to flexion? | Gastrocnemius, plantaris, sartorius, gracilis |
| What are the symptoms of genu recurvatum (quads paralysis)? | Can't extend leg against resistance - hyperextension |
| What are the symptoms of chonodromalacia patellae? | Soreness and aching around patella from muscular imbalance of quads. Usually weak vastus medialis |
| Which side does the patella usually move to during a dislocation? | Lateral |
| What kind of joints are the 3 knee joints? | Synovial condylar - medial/lateral tibio-femoral joint; Synovial planar - patellar femoral joint |
| Compare the size of the condyles of the femur | Medial is bigger than lateral but lateral is more elongated and project more anteriorly |
| What is the implication of the size difference of the condyles? | Amount of movement on tibial condyles against femoral condyle could be different because lateral is longer |
| Describe the articular surface of the femur for the knee joint | Articular surface represents a segment of a pulley which recalls the twin undercarriage of an airplane. The two femoral condyles, convex in both planes and form the lips of the pulley and are extended anteriorly by the pulley-shaped patellar surface |
| Describe the articular surface of the tibia | Reciprocally curved and comprise 2 curved & concaved parallel gutters separated by blunt eminence. The eminence lodges the two intercondylar tubercles and if we prolong this eminence, it coincidies with vertical ridge on deep surface of the patella |
| What must happen to the articular surfaces of the knee to allow axial rotation? | Tibial surface must be so modified as to shorten the intercondylar eminence that's achieved y planning the two ends of the eminence and leaving its middle part to act as a pivot which by lodging the intercondylar notch, allows tibial rotation |
| Describe the knee joint capsule | Composed of complex passive and active connections among the minisci, ligaments, retinacula, bones, muscle, and capsule itself - forms sleeve around joints, attaching just above femoral condyles and below tibial condyles |
| What reinforces the joint capsule? | Retinacula and ligaments which become integral parts of capsule |
| What does the retinacula retain and against what? | Retains patella against the femur |
| What is the range of motion for flexion of the knee joint? | 135-150 degrees - depending on muscle mass in calf and posterior thigh |
| What is the range of motion for knee hyperextension | 5-15 degrees |
| What position does the knee have to be in for considerable amount of rotation to occur? | Knee flexion to 90 degrees |
| Describe the axis for rotation for the knee joint | Longitudinal and located medial to intercondylar eminence of tibia |
| What can be said about the axis of rotation since it is located medial to intercondylar eminence of tibia? | That lateral condyle rotates around the medial condyle |
| What limits the motion of rotation of the knee joint? | Capsule and ligamentous structures: collateral, cruciate, oblique popliteal ligaments, retinacula, and IT band |
| What is the automatic (screw-home mechanism)? | Inevitable and involuntary axial rotation linked to movements of flexion and extension |
| What kind rotation happens during knee extension? | Lateral rotation at end of extension |
| What kind of rotation happens during knee flexion? | Medial rotation at start of flexion |
| What is the range of motion for active lateral rotation? | 30-40 degrees |
| What is the range of motion for active medial rotation? | 20-30 degrees |
| During lateral rotation, what direction is the lateral meniscus pulled towards? | Anteriorly |
| During lateral rotation, what direction is the medial meniscus pulled towards? | Posteriorly |
| During medial rotation, what direction is the lateral meniscus pulled towards? | Posteriorly |
| During medial rotation, what direction is the medial meniscus pulled towards? | Anteriorly |
| What can happen if there was violent extension of the knee especially if it is accompanied with lateral/medial rotation of tibia? | May result in longitudinal splitting, complete detachment, complex tear, transverse tear |
| What kind of bone is a patella? | Sesamoid bone |
| What does the patella articulate with? | anterior and distal saddle-shaped surface of femoral condyles |
| How can the patella increase the leverage or torque of the quadriceps muscles? | By increasing its distance from axis of rotation |
| When can the patella provide bony protection to the distal femoral condyles? | When knee is flexed |
| What effect does the patella have on the femur? | Can decrease pressure and distribute forces on the femur |
| How can the patella help protect quadriceps from damage? | Prevents damage from compression during full range resisted knee flexion/extension since the tendon wasn't designed to withstand compression forces but large tension forces |
| Where is the patella during knee flexion? | Compressed against patellar groove |
| Where is the patella during knee extension? | Detaches from femur |
| Why does the patella have the tendency to dislocate laterally? | Because of obtuse angle between quadriceps tendon and patellar ligament |
| What prevents lateral displacement of the patella? | Vastus medialis and lateral lip of the patellar groove which is higher than medial lip |
| What anchors the patella to the tibial tuberosity? | Strong patellar ligament |
| How does the vastus medialis prevent lateral displacement of the patella? | Keeps patella on track in gliding on the femoral condyles by counteracting the laterally displaced forces of vastus lateralis |
| What is the role of gluteus maximus, in respect to genu recurvatum? | Can be used as a strong extensor of the hip and to maintain the knee in the extended position during walking |
| What is a transverse patellar fracture? | Fracture of patella in two pieces from a powerful quadriceps contraction - proximal piece pulled superiorly while distal piece remains with patellar ligament |
| What is the implication of removing the patella? | Quadriceps having to exert about 30% more force to extend the leg |
Created by:
nnguyen44
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