Knee Anatomy PDF

KNEE ANATOMY PT7001  Learning Outcomes After this lecture you should be able to:  Describe the bony anatomy of the knee joint, including the shape of the articular surfaces 1  Know that the femoral and obturator nerves may refer knee pa...

KNEE ANATOMY PT7001  Learning Outcomes After this lecture you should be able to:  Describe the bony anatomy of the knee joint, including the shape of the articular surfaces 1  Know that the femoral and obturator nerves may refer knee pain to the hip and vice-versa  Describe the patello-femoral joint and list its common clinical problems 2  Define the terms “genu valgum” and “genu varum”  Know the position, shape and functions of the menisci, and give an account of their common injuries 3  Give an account of the movements of the tibiofemoral joints  Describe the ligaments of the knee joint and give their functions 4  Describe the capsule and synovium of the joint, and list the bursae associated with it. Know the symptoms and signs of  Part 1 Knee Joint Part 1: Overview and Knee Dislocation  The Knee Joint Overview  Hinge joint (modified)  Stable due to intra & extra- capsular ligaments  Articulation points: - patellofemoral joint - med & lat tibiofemoral joints  Not ideally congruent - potential for femoral condyles to slip off the plateaus  The Knee Menisci  Intra-synovial articular discs  Joint surfaces are made more stable by presence of menisci  Wedge-shaped - help to deepen socket for more congruency, support  Shock absorbency … more later  Muscles Crossing the Knee Joint  Produce movement across knee  Enhance joint stability  Anterior - quadriceps group crosses knee via patella - extends knee  Posterior - hamstring & gastrocnemius, popliteus, (plantaris)  Muscles Crossing the Knee Joint VL RF BF ST VL VM (L) BF Gr SM (L) BF ITB (S) VL VM Gr ST ITB S PL S SM G Pop G G G ANTERIOR LATERAL POSTERIOR MEDIAL  Normal Range of Movements of the Knee 30-40o 10o Flexion / extension 0 - 135o Pain, oedema, muscle bulk can restrict MODIFIED HINGE JOINT  Vasculature of the Knee Joint  Blood supply is from: Popliteal artery - anastomoses (branches) of the popliteal artery - descending branches of genicular arteries (5) from hip & thigh (genu = Latin for knee) (posterior) - popliteal artery branches from femoral a.  Neurovasculature of the Knee Joint  Capsule is innervated by 4 nerves Anterior - femoral nerve Posterior - obturator nerve - tibial nerve - common fibular nerves  FEMORAL & OBTURATOR nerves also supply the hip joint so can often get referred pain from one joint to the other  Retinaculae of the Knee Joint  Fibrous bands of thick fascia  Externally to the capsule the knee is supported by collateral ligaments  Patellar tendon acts like a ligament supporting the front of the joint (often ligamentum patellae)  Fat pad behind the patellar T. prevents the synovium from escaping anteriorly - also fills gap  Additional support by the quadriceps tendon continuations crossing downwards over the joint - these are the medial & lateral retinaculae - keep fat pad & synovium in place.  Capsule of the Knee Joint  Posteriorly strong capsule  - supported by oblique popliteal lig. & arcuate lig. …more ligaments later Oblique popliteal ligament Arcuat e ligame nt  Knee Dislocation Posterior tibiofemoral dislocation  rupture of 3 or 4 ligaments  popliteal artery at risk  The Patello-Femoral Joints  Patella = sesamoid bone, upside-down triangle (base at top superiorly, apex at bottom)  Quads T. attaches to the base (top)  Patella T. attaches to apex (bottom)  Patella only articulates between the femoral condyles - groove (trochlea). Not at all with tibia.  Med & lat patellofemoral joints at reverse of patella…  The Patello-Femoral Articular Surfaces  Med & lat articular surface of the patella for each femoral condyle with a vertical ridge in between M L  Lat femoral condyle projects more anteriorly and is larger - therefore patella articular surface is larger The Sunrise View Left leg  Patello-Femoral Dislocation  Most patella dislocs are lateral as medially the patella is very stable  MOI - sudden medial rotation  In normal knee, quads muscle pulls the patella upwards via the quads tendon - this is in exactly the same direction as the rec fem fibres  - but, vastus lat & intermedius pull the patella laterally  patella potentially deviates & causes disloc  this is prevented by 2 factors…  Patello-Femoral Dislocation … this is prevented by 2 factors:… 1. lat femoral condyle is larger 2. vastus medialis fibres insert almost horizontally to the medial border of the patella to correct the pull of the other muscles  In some sports (e.g. cycling) this medial pull can be too much Signs of Patello-Femoral Dislocation  Q-Angle  The femur is angled so the quads muscle pulls along the mechanical axis  Creates an angle across the knee joint - Q-angle (quadriceps angle)  Can also be affected by - excessively wide hips - abnormally placed knees (knee valgus, tibial torsion) - mal-positioned patella (high-riding (patella alta) or displaced)  Measuring Q-Angle  Line through the center of the patella to the ASIS and another line from the tibial tuberosity through the center of the patella.  The intersection of these two lines is the Q-angle  Normative value is 13° to 18°  Females have wider hips, so angle is greater  High Q-angle puts enormous strain on the patella (fulcrum, force) = prone to dislocation  Knee Angles  Genu = Latin for knee  Genu valgum / knee valgus / knock knees  Increased Q-angle  Stresses MCL  Increase pressure on bone & cartilage on lateral side genu valgum  Knee Angles  Genu varum / knee varus / bow legs  Stresses LCL  Can lead to tearing of the meniscus genu varum The Knee Joint Self-Assessment Questions Pt 1 1. What exactly is the patella, and why is it there? 2. Name two factors which help prevent patello- femoral dislocation. 3. What do the terms ‘genu valgum’ and ‘genu varus’ mean?  Part 2 Knee Joint Part 2: Tibiofemoral Joints  Tibiofemoral Joints  Hinge - 2 articulations - med & lat. Femoral condyles with tibial condyles. Condyles = Greek for knuckle. Tibial condyles misnamed because they are flat plateaus  The Menisci  Fibrocartilaginous pads  Compensate for the incongruence of the articular surfaces of the TFJ.  Post & ant horns attach to the sides of the tibial intercondylar eminence  Thicker around periphery - wedge shape  Med meniscus C-shaped, lat is O-shaped  Med meniscus additionally attached to deep part of MCL (why can often injure both structures)  2 anterior horns attached to each other by transverse genicular ligament  Between the anterior horns - attachment of ACL  Between posterior horns - PCL  Functions of the Menisci  Increase congruency - stability  Shock-absorbers  Aid lubrication - synovial fluid  Tears of the Menisci  Common, as menisci are subject to great forces placed upon them  Many diff types of tear - can be along longitudinal, horizontal or radial axis  Lat meniscus is freer to move than med (not bound by lig.) so is less likely to be torn as can adapt to excessive forces. (Med attached to deep MCL)  Bucket-handle Tear  Most common tear = bucket handle tear - leaves a medial segment which can flip over - gets in the way of articulations & knee may not fully extend.  Red Zones of the Menisci  Direct relationship between vascularisation & capacity to heal.  Red zone more vascularised so heals better.  Tibio-Femoral Joint L L A P P A M M  Joint is fully flexed and pulled apart  The most anterior part of the fem condyle is reserved for the patella  Tibio-Femoral Joint  During walking, to move from flexion to extension there is a combination of rolling and gliding within this joint  the lateral side (orange) uses up its articular surface quicker than the medial (green) side  the medial continues into extension until its surface is used up  this causes medial rotation of the femur on the tibia in the final 15° of extension  the rotation causes tightening of all the ligaments  joint becomes solid and stable = close- packed position  Popliteus Muscle  Once the joint is locked in full extension, it needs to be rotated the other way in order to be unlocked  the popliteus muscle does this - it laterally rotates the femur  Triangular muscle at back of tibia, inserts into lat femoral condyle and actually pierces the capsule here and attaches inside  at this point is a thickening of the capsule = arcuate ligament, part of the posterolateral ligament complex  Popliteus is supplied by the tibial nerve The Knee Joint Self-Assessment Questions Pt 2 1. What are the main differences between the medial and lateral femoral condyles? 2. Why is the medial meniscus 20 times more likely to be injured than the lateral meniscus? 3. What is the action of the popliteus muscle?  Part 3 Knee Joint Part 3: Ligaments of the Knee Joint  Collateral Ligaments  LCL  MCL  thinner cord-like  flat strap  attached proximally  2 bands to lateral epicondyle  superficial band from and distally to head of fibula med epicondyle of femur & inserts distally onto proximal shaft of tibia  deep band - same but also anchored to medial meniscus  Collateral Ligaments Function  Prevent sideways movement of the joint - against varus or valgus force  Collateral ligaments are taut in full extension & relaxed during flexion  In normal walking it is in LCL MCL extension that body load is applied to the joint so this is when it needs most support  Additional support is provided by… 1. 3. 1. 5. 4. 6. also med 2. Pes Anserinus tendons head of gastroc (goose foot) Valgus Stress Test  When seated (knee flexion) there is little support from muscles or ligaments (relaxed), so must test the ligament in extension  Valgus stress test - stresses MCL  Varus Test Stress  Varus stress test - stresses LCL  Cruciate Ligaments Crux = Latin for cross  ACL - anterior intercondylar ridge of tibia  inserts lateral surface of medial femoral condyle posteriorly HAND IN TROUSER POCKET direction  PCL - posterior intercondylar ridge of tibia  inserts lateral surface of medial femoral condyle anteriorly TRANSVERSE VIEW POSTERIOR VIEW ACL ACL PCL PCL ACL POSTERIOR VIEW PCL MEDIAL VIEW ACL PCL  Anterior Cruciate Ligament  ACL prevents anterior displacement of the tibia in relation to the femur  Is subject to great stress during full extension - taut, and tightened even more by locking mechanism  Posterior Cruciate Ligament  PCL does the opposite - prevents posterior translation of the tibia / excessive fwd movement of femur  PCL approx 3 times thicker than ACL  When walking/running, knee is partially flexed as we begin to transfer body weight onto the limb  at that moment 2 structures are helping to keep the femur from slipping forward… o PCL o tightness of the extensor mechanism - quads is contracting = patellar T. stretched firmly across front of joint  Cruciate Ligament Injury  When knee is extended, ligaments are taut - if sudden additional medial twisting when foot is planted  ligaments are subject to injury  ACL thinner so more prone to injury  The ACL receives its blood supply from branches of the middle genicular artery, which form a vascular synovial envelope around the ligament. These periligamentous vessels penetrate the ligament transversely  Both ligaments have vascular zones (inferior geniculate artery) and if ruptured can leak blood inside the joint capsule = haematoma  swelling, pain, discolouration of joint  The Lachman’s Test  Knee at 30° so hamstring relaxed  Evaluates ACL rupture  The Unhappy Triad  ACL + MCL + medial meniscus  from lateral force or twisting in extension The Knee Joint Self-Assessment Questions Pt 3 1. Name five structures which protect the lateral side of the knee joint? 2. Which ligament is taut during flexion of the knee? 3. Which 3 structures are involved in a classical ‘unhappy triad’?  Part 4 Knee Joint Part 4: Bursae of the Knee  Synovium of the Knee Joint  The cruciate ligaments and popliteal tendon are inside the capsule - but lie OUTSIDE the synovial membrane (intra-capsular but extra-synovial)  cruciate ligaments get access to a blood supply  Infrapatellar Fat Pad  Infrapatellar fat pad (Hoffa’s fat pad) (intracapsular, extrasynovial) - outside synovium, behind patellar tendon. Synovium sits on top.  Fat pad acts as cushion, prevents Infrapatellar friction, fills the gap fat pad for stabilisation  Richly vascularised Infrapatellar Fat Pad Attachments  Bursae of the Knee Joint  Lots around knee - most Medial view protect tendons where they lie close to the bone  Prepatellar bursa protects the skin  4 in continuity with joint - suprapatellar, semimembranosus, gastrocnemius, popliteal  Commonly the semimembranosus bursa & the gastrocnemius bursa are combined  Popliteus Bursa  Protects the popliteal tendon as it winds laterally under LCL to reach the lateral epicondyle of femur  Enlargement of these bursae - inflammation  swelling = Baker’s Cyst  Can occur following any knee inflammation, but is commonly associated with inflammatory reaction in late stages of osteoarthritis of knee Popliteal (Baker’s) Cyst  Anserine Bursa  Most common bursa to be affected by running - constant friction, excessive rotation, valgus stress Suprapatellar Bursitis Pre-Patellar Bursitis Infrapatellar Bursitis  Treatment for Bursitis  Excess fluid removed by aspiration, and NSAID agents are used to treat the inflammation The Knee Joint Self-Assessment Questions Pt 4 1. Name four bursae that are continuous with the cavity of the knee joint. 2. Which bursa may be inflamed if there is pain on the medial side of the joint? 3. Which bursa is inflamed in Clergyman’s Knee?