PT 500 Knee and Popliteal Fossa PDF

Popliteal Fossa and Knee 1 PT 500: Human Anatomy Popliteal Fossa and Knee 1. Surface Anatomy of the Knee a. Anteriorly i. Patella (pat...

Popliteal Fossa and Knee 1 PT 500: Human Anatomy Popliteal Fossa and Knee 1. Surface Anatomy of the Knee a. Anteriorly i. Patella (patellar position, alignment, size, shape) ii. Patellar tendon/ligament and Joint line b. Laterally i. Lateral epicondyle of femur, tibial condyle, and LCL ii. Tendon of biceps femoris iii. Identify the path of the IT band as it inserts into the tibia c. Medially i. Medial epicondyle of femur, tibial condyle, and MCL ii. Tendon of gracilis Review the pes anseriunus d. Posteriorly i. Notice the boundaries of the diamond shaped popliteal fossa 2. Popliteal Fossa a. Boundaries i. Superomedially: semitendinosus and semimembranosus ii. Superolaterally: biceps femoris iii. Inferiorly: Medial and Lateral heads of Gastrocnemeus iv. Roof: Fascia and skin v. Floor: popliteal surface of femur, the popliteus fascia and oblique popliteal ligament, and the posterior aspect of the proximal tibia Section 1 Popliteal Fossa and Knee 2 b. Contents i. Fat ii. Sciatic n and its bifurcation into: 1. the tibial n 2. the common fibular n iii. The sural nerve iv. The popliteal artery and vein (and genicular branches) v. The anterior and posterior tibial arteries and veins vi. The lesser saphenous vein (joins popliteal vein here) vii. Lymph nodes viii. The popliteal bursa Section 1 Popliteal Fossa and Knee 3 Section 1 Popliteal Fossa and Knee 4 3. Patellofemoral Joint a. PFJ Joint Structure i. Planar Gliding Joint ii. Joint Surfaces 1. Articular facets of patella a. Inferior, middle and superior facets b. Medial facet = “odd facet” c. Number of facets can vary d. Base of the patella is the superior aspect; Apex is the rough inferior aspect 2. Patellar Surface of Femur Section 2 Popliteal Fossa and Knee 5 iii. Patellofemoral Contact 1. In full extension there is very little contact b/t patella and femur 2. At 10°-20° of flexion, the inferior facets contact 3. Middle facets contact with partial flexion 4. Superior facets contact around 90° of flexion 5. Medial/Odd facet contacts at 135° (full) flexion iv. PFJ Joint Function 1. Patella increases quads mechanical advantage by serving as a pulley Section 2 Popliteal Fossa and Knee 6 b. PFJ Joint Reinforcements i. Bony Congruency of articular surfaces ii. Patellar tendon and ligament iii. Medial and lateral retinacula 1. Composed of fibers from the vasti medialis and lateralis, fascia lata and capsule. 2. Lateral retinaculum may have strong attachments to the ITB Section 2 Popliteal Fossa and Knee 7 4. Knee Joint (Tibiofemoral Joint) a. Osteology/ Joint Surfaces i. Joint Structure/Classification 1. Modified hinge type or bicondyloid joint. 2. During development, two synovial membranes are formed, but later fuse into one ii. Osseus Surfaces 1. Femoral: a. Medial femoral surface is larger and oval b. Lateral surface is circular. c. The intercondylar fossa has a groove for the patella. d. The medial condyle is more distal than the lateral. 2. Tibial: a. Lateral surface is circular and smaller than the medial; b. Medial surface is oval and longer along the A-P axis. c. Grooves for the attachment of the semimembranosus and another more inferiorly for the popliteus are located on the posterior surface. Section 3 Popliteal Fossa and Knee 8 Section 3 Popliteal Fossa and Knee 9 b. Capsule, Synovium and Fat Pads i. Capsule: External Fibrous Layer 1. Encloses condyles of femur and articular surfaces of the tibia 2. Reinforced medially and laterally by the retinacula (see above) 3. The capsule is deficient anteriorly, deep to the patella and attaches to the menisci. a. The suprapatellar bursa is part of the capsule. ii. Synovium 1. Lines all surfaces of the joint capsule, but reflects over the intercondylar area almost dividing the joint in two cavities 2. The cruciate ligaments and infrapatellar fat pad are thus intracapsular but extrasynovial (outside of the synvial cavity) Section 3 Popliteal Fossa and Knee 10 Section 3 Popliteal Fossa and Knee 11 iii. Bursa 1. Anteriorly: Prepatellar, infrapatellar (deep and subcutaneous) and suprapatellar bursa 2. Bursae between many of the tendons around the knee as well including: a. Between LCL and biceps femoris tendon b. Between MCL and pes anserinus tendons 3. Suprapatellar, popliteus, anserine, and gastrocnemius brusae communicate with the knee joint synovial cavity a. Why is this important clinically? iv. Fat Pads 1. Infrapatellar, suprapatellar and others Section 3 Popliteal Fossa and Knee 12 c. Ligaments i. Anterior Cruciate Ligament (ACL) 1. Attachments of the ACL a. Anterior intercondylar area of tibia i. Has a slip connecting to anterior aspect of lateral meniscus b. Posterior aspect of medial surface of lateral femoral condyle c. Within the joint capsule but outside the synovial cavity (intracapsular, extrasynovial) 2. Function of the ACL a. Restrains posterior rolling of the femoral condyles on the tibia (converts the roll to a spin) b. Limits anterior translation of the tibia on the femur c. Limits extension of the knee d. Limits abduction of the tibia (valgum at the knee) Section 4 Popliteal Fossa and Knee 13 ii. Posterior Cruciate Ligament (PCL) 1. Attachments of the PCL a. Posterior aspect of intercondylar area of tibia b. Anterior aspect of lateral side of medial femoral condyle c. Passes medially to the ACL at their crossover d. Posterior Meniscofemorial Ligament i. Slip from posterior horn of the lateral meniscus to PCL 2. Function of the PCL a. Limits posterior displacement of the tibia on the femur b. Different portions of the ligament are taught in flexion or extension Section 4 Popliteal Fossa and Knee 14 iii. Combined Function of the Cruciate Ligaments 1. Some portion of ACL or PCL is under tension at all times  maintains contact of tibial and femoral surfaces 2. The crossover point of the ACL and PCL creates the axis of rotation for the tibia iv. Lateral Collateral Ligament (LCL) 1. Attachments of the LCL a. Lateral epicondyle of femur b. Lateral surface of fibular head 2. Structure of the LCL a. Cord-like b. Extra capsular (though has attachment to capsule at superior attachment) c. Superficial to popliteus tendon, lateral genicular artieries and nerves d. Deep to biceps femoris tendon (blend at insertion) 3. Function of the LCL a. Limits adduction of tibia (varus stresses) b. Limits tibial rotation (in knee flexion) Section 4 Popliteal Fossa and Knee 15 Section 4 Popliteal Fossa and Knee 16 v. Medial Collateral Ligament (MCL) 1. Attachments of the MCL a. Medial epicondyle of femur b. Medial condyle of tibia (superficial fibers) c. Superior part of medial surface of tibia (at pes anserinus) (deep fibers) 2. Structure of the MCL a. Flat band b. Weaker than LCL c. Intrinsic to capsule (part of the fibrous capsule) d. Deep fibers have attachment to medial meniscus i. What are the implications of this in the case of injury? 3. Function of the MCL a. Limits abduction of tibia (valgus forces at knee) b. Lax at 90° of flexion c. Limits tibial rotation (in knee flexion) vi. Other Ligaments 1. Oblique Popliteal Ligament a. Reflection of tendon of semimembranosus b. Additional reinforcement for posterior capsule 2. Arcuate Ligament a. Passes over popliteus tendon b. Arises from posterior aspect of fibular head  blends with posterior capsule c. Reinforces posterior joint capsule Section 4 Popliteal Fossa and Knee 17 d. Menisci i. Medial Mensicus 1. Attachments a. Anterior intercondylar area of tibia and posterior intercondylar area of tibia b. Has attachment to MCL c. Semimembranosus has attachment to posterior aspect of meniscus 2. Semilunar in shape and less mobile than lateral meniscus ii. Lateral Meniscus 1. Attachments a. Anterior intercondylar area of tibia (some fibers blend with ACL) b. Posterior intercondylar area of tibia (anterior to attachment of medial meniscus) c. Popliteus has attachment to the posterior aspect 2. Circular in shape and more mobile than medial meniscus Section 4 Popliteal Fossa and Knee 18 iii. Functions of the Menisci 1. Improve distribution of weight bearing forces in the joint ( point stress) 2. Increase stability of the joint 3. Absorb shock 4. Reduce friction 5. Mensici migrate posteriorly during knee flexion (as weight bearing surface of femur shifts posteriorly on tibia) iv. Ligaments associated with the Mensci 1. Coronary Ligaments a. Attach menisci to tibia 2. Transverse Meniscal Ligament a. Joins the anterior horns of the medial and lateral mensici Section 4 Popliteal Fossa and Knee 19 e. Movements of the Knee Joint i. Arthrokinematics of the knee joint 1. In open chain flexion, the tibia rolls and glides posteriorly on the femoral condyles 2. In closed chain flexion, the femoral condyles roll posteriorly and glide anteriorly (due to tension in ACL) on the tibia 3. Stay tuned for way more on arthrokinematics in your movement science class! ii. Locking the Knee (screw home mechanism) 1. In terminal extension (last 30° of extension) tibia rotates laterally (in open chain) 2. Occurs due to the asymmetry of the medial and lateral condyles a. Lateral condyle spins, medial condyle continues to roll 3. In full extension tibial tubercles fit in intercondylar groove, ligaments are taut and menisci interposed between tibial and femoral condyles = closed packed position a. Closed packed = position of greatest joint congruence and ligamentous tightness  typically most stable position f. Blood Supply to the Knee Joint i. Genicular anastomoses 1. Genicular arteries (branches of Popliteal artery): a. Superior lateral b. Superior medial c. Inferior lateral d. Inferior medial e. Middle 2. Anastamoses (connect/ network) with a. Descending genicular artery (off femoral) b. Descending branch of lateral circumflex femoral c. Anterior tibial recurrent Section 5 Popliteal Fossa and Knee 20 Section 5 Popliteal Fossa and Knee 21 g. Clinical Considerations for the Knee Joint i. Torn cruciate ligaments- common injuries. You will learn how to test for ligamentous laxaity in your clinical courses. ii. Torn menisci- usually the medial meniscus is torn (with the medial collateral ligament). Floating pieces of cartilage may then be found in the knee joint and require removal as they impinge on joint movement. iii. Torn collateral ligaments- more commonly the medial collateral is torn. iv. Impingement/irritation of the common peroneal nerve as it passes around the fibular head. v. Patellofemoral syndrome vi. Patellar tendonitis (and Osgood Schlotters) vii. DJD/osteoarthritis of the knee Section 5