The Knee Joint

Classification of the joint Modified hinge-type synovial joint Motions Flexion/Extension Some internal/external rotation – primarily during knee flexion

Articulating surfaces of the knee Femur Large curved condyles covered with smooth hyaline cartilage with a gap in between – intercondylar notch

Patella Anterior surface covered by part of quadriceps tendon Tendon forms the superficial part of the patellar ligament

Patella Posterior surface Medial facet Lateral facet Articulates with the patellar articulating surface of the medial condyle of the femur Odd facet Lateral facet Articulates with the patellar articulating surface of the lateral condyle of the femur Non-articulating area Distal to the pole or apex where the patellar ligament attaches Fat pad of knee joint is deep to the distal pole of the patella

Borders of Patella Superior Medial Lateral Inferior – Apex of patella

The Tibia Superior Articular Surface Medial facet (medial condyle) Shape: Articulates with: Meniscus –

Tibia pic Medial side

Lateral facet Shape: Articulates with: Meniscus:

Intercondylar eminence Separates the medial and lateral facets of the tibia Prevents:

Intercondylar areas Anterior intercondylar area Attachment: Posterior intercondylar area

Other parts of the tibia Tibial tuberosity Medial epicondyle Posterior groove Medial surface

Lateral epicondyle Lateral surface Posterior surface Articular facet for fibula Not part of the knee joint Non-articular surface

Lateral tibial epicondyle cont. Non-articular surface Popliteus muscle crosses this surface The muscle travels deep to the fibular collateral ligament

More knee joint General movements Articular capsule of the knee joint Patellar ligament LCL and MCL Other ligaments of knee joint Bursae ACL and PCL Menisci Blood and nerve supply to the knee joint

Movements of the knee joint Flexion Limits: Effects of skin Rotation Greatest during:

Extension Limits: Full extension Unlocking the knee Tibial rotation in open chain Femoral rotation in closed chain Unlocking the knee

Articular capsule of the knee joint Attachments of the joint capsule Superiorly

Inferiorly The capsule is prolonged inferolaterally over the popliteus muscle to the head of the fibular forming the arcuate popliteal ligament

Ligaments of the joint capsule 5 intrinsic (at least in part) ligaments that are external and strengthen and supplement the joint capsule Patellar ligament Fibular collateral ligament Tibial collateral ligament Oblique popliteal ligament Arcuate popliteal ligament

Patellar ligament Strong thick band (though thin in some people) Continuation of the: Relation to the joint capsule Infrapatellar fat pad: Deep infrapatellar bursa Patella – sesamoid bone

Fibular Collateral Ligament AKA: Lateral collateral ligament Dimensions Length Attachments

FCL (LCL) The tendon of the biceps femoris is split in two by the LCL To locate the inferior attachment, follow the tendon of the biceps femoris muscle FCL separated from the joint capsule inferiorly by fatty tissue Tendon of popliteus muscle passes deep to the FCL, separating it from the lateral meniscus (see next picture)

Superiorly the FCL is fused with the fibrous joint capsule of the knee joint, and this part is considered to be an intrinsic ligament

Tibial (Medial) collateral ligament Dimensions Length

MCL Attachments Proximal Distal

Deep fibers of the MCL attached to the: Injury to the MCL is frequently associated with injury to the medial meniscus and the ACL Blow to lateral knee Bursa in MCL which is of clinical significance during post-MCL sprain recovery

Stress on fibers Because the MCL is wide, the fibers can be stressed during knee movement Anterior fibers stressed during: Posterior fibers stressed during:

Oblique Popliteal Ligament Posterior medial ligament Extension of semimembranosus tendon Travels superolateral to insert into central part of capsule Strengthens posterior capsule

Arcuate popliteal ligament Posterior lateral ligament Arises from posterior part of head of fibula Travels superomedial over tendon of popliteus muscle to attach to intercondylar area of tibia and lateral epicondyle of femur

Synovial capsule and bursae of the knee Synovial capsule lines the fibrous joint capsule Synovial capsule attaches to the: The synovial cavity of the knee is the largest one in the body

Note that the synovial capsule is reflected around the cruciate ligaments

Bursae Sacs lined with synovial membrane and filled with synovial fluid May connect with the synovial cavity of a joint Function:

Four bursae communicate with the synovial cavity of the knee joint They lie deep to the tendons of the: Quadriceps femoris muscles (suprapatellar bursa) Popliteus muscle (popliteus bursa) Gastrocnemius muscle Semimembranosus muscle

Suprapatellar bursa Superior extension of synovial capsule Between: Extends superior to base of patella Permits free movement of muscle over distal femur: allowing for full flexion/extension Held in place:

fig Suprapatellar bursa

Popliteus bursa Between tendon of the popliteus muscle and the lateral condyle of the tibia Opens into lateral part of synovial cavity inferior to the lateral meniscus

Gastrocnemius bursa Extension of synovial cavity Lies deep to attachment of the medial and lateral heads of the gastrocnemius muscle, separating the tendon from the femur

Semimembranosus bursa Frequently a prolongation of the gastrocnemius bursa Separates: Communicates with the joint cavity Location of the popliteal or Baker’s cysts

Bursae which do not communicate with the synovial cavity Anserine bursa Complicated structure with many sacs or pouches (diverticula) Separates the common tendon from the proximal part of the medial tibia and MCL

Anserine bursa

Subcutaneous prepatellar bursa Location Allows Disorder Subcutaneous infrapatellar bursa Withstands pressure during

Deep infrapatellar bursa Location Separated from knee joint by the infrapatellar fatpad Infrapatellar fatpad

bursa

Cruciate ligaments of the knee joint Very strong ligaments located within the fibrous joint capsule of the knee They are NOT within the synovial cavity of the knee Rounded ligaments Located between the medial and lateral femoral condyles The ACL and PCL cross each other in an oblique orientation

Anterior Cruciate Ligament Attachments On tibia Travels superiorly, posteriorly and laterally On femur

ACL Relatively slack during: Relatively taut : Prevents

Posterior Cruciate Ligament Stronger than ACL Attachments On tibia: Travels superiorly and anteriorly on the medial side of the ACL On femur

PCL pic

PCL strain increases: Strain relatively decreases: Posterior meniscofemoral ligament

Prevents Main stabilizer of femur in the flexed knee Walking downhill, downstairs

Menisci Crescent or wedge-shaped fibrocartilaginous structures Attached to: Coronary ligaments : Transverse ligament of the knee:

Menisci pic

Function The tibial condyles are flat or slightly curved.

Blood supply to the menisci Periphery: Arteries Inner edge

Medial meniscus Broader posteriorly than anteriorly Anterior attachment Anterior intercondylar area of tibia Anterior to attachment of ACL Posterior attachment Posterior intercondylar area of tibia Anterior to attachment of PCL

Mobility of Medial Meniscus Less mobile than Lateral meniscus Firmly attached to deep surface of the tibial collateral ligament Attachment sites are separated from each other How would this affect mobility

The Lateral Meniscus Smaller than medial meniscus More freely movable Though it covers a larger articular surface area of the tibia More freely movable Tendon of popliteus muscle Attachment sites are attached closely together on the tibia Posterior meniscofemoral ligament:

Blood supply to the knee joint Middle genicular artery and the medial and lateral branches of the inferior genicular artery (branches of the popliteal artery) Pierces the fibrous joint capsule and supplies

Nerve Supply to the Knee Joint Articular nerves are branches of the: Obturator nerve Femoral nerve Tibial nerve Common Fibular (Peroneal) Nerve

Special Region of the Knee Popliteal Fossa Diamond-shaped region posterior to the knee joint Posterior to: Distal 1/3rd of femur Knee joint Proximal tibia

Borders of the popliteal fossa Superomedial Superolateral Inferomedial Inferolateral

Walls of the popliteal fossa Posterior part of fossa Superficial popliteal fascia Deep popliteal fascia Floor of fossa

Superficial popliteal fascia Contains Fat Vein – 3 nerves Posterior femoral cutaneous nerve Medial sural nerve Lateral sural nerve

Deep popliteal fascia Strong, dense sheet of deep fascia Protects deep neurovascular structures passing from thigh to leg Pierced by small saphenous vein

Floor of popliteal fossa Popliteal surface of femur Fascia of popliteus muscle Oblique popliteal ligament (medially)

Contents of popliteal fossa Popliteal artery Popliteal vein Nerves – branches off the sciatic nerve

Popliteal Artery Continuation of the femoral artery after it passes through the adductor hiatus Branches Medial superior genicular aa. (VL and femur) Lateral superior genicular aa. (VM and femur) Middle genicular aa. (menisci and cruciates Medial and lateral inferior genicular aa. (menisci and cruciates) Muscular branches to hamstrings, gastrocnemius, soleus and plantaris muscles

Popliteal Vein Ascends from medial side of popliteal artery to the lateral side Ends at the adductor hiatus where it becomes the femoral vein

Nerves in the popliteal fossa Sciatic nerve

Tibial Nerve Genicular nerves Muscular branches Follow branches of genicular arteries Muscular branches Popliteus, gastrocnemius, plantaris and soleus muscles Medial sural cutaneous nerve Between heads of gastrocnemius muscle

Common fibular nerve Follows: Divides into superficial and deep fibular nerves in the leg Most commonly injured nerve in the lower extremity Lateral sural cutaneous nerve

Sural cutaneous nerve Formed from medial and lateral sural cutaneous nerves What does sural mean?

Injury to common fibular nerve

Injury to tibial nerve