Knee Conditions Chapter 15

Anatomy Large synovial joint Two condylar articulations Gliding joint Medial tibiofemoral joint Lateral tibiofemoral joint Gliding joint Patellofemoral joint

Bones Femur Tibia Fibula Medial epicondyle Lateral epicondyle Linea aspera Tibia Medial tibial plateau Lateral tibial plateau Fibula

Tibiofemoral Joint Modified hinge joint allowing some lateral and rotational motions to occur as well. Lateral epicondyle is larger than medial. Because of size difference there is a screwing home mechanism to bring the knee into full extension.

Menisci Semilunar fibrocartilage (half moon shapes) Attach to the superior plateaus of the tibia. Absorption and dissipation of force Lubrication Medial meniscus is semicircular and attaches to the medial collateral ligament Lateral meniscus is almost a complete circle and attaches to the posterior cruciate ligament

Bursae Suprapatellar bursa, lies between the femur and quadriceps femoris tendon Subpopliteal bursa, lies between the femur and the popliteal muscle Semimembranosus bursa, lies between the medial head of the gastrocnemius and the semimembranosus tendon. Prepatellar bursa, lies between the skin and the anterior surface of the patella

Bursae continued Superficial infrapatellar bursa is located between the skin and the patellar tendon. Deep infrapatellar bursa is located between the tibial tubercle and the infrapatellar tendon.

Ligaments Anterior Cruciate Ligament (ACL), attaches anteriorly on the tibia, and to the posterior surface of the lateral femoral condyle. Prevents: Anterior translation of the tibia on a fixed femur Posterior translation of the femur on a fixed tibia Internal and external rotation of the tibia on the femur Hyperextension of the tibia

Ligaments continued Posterior Cruciate Ligament (PCL), attaches posteriorly to the tibia, and to the anterior surface of the lateral medial condyle of the femur. Prevents: Posterior displacement of the tibia on a fixed femur.

Ligaments continued Medial collateral ligament (MCL) connects from the medial condyle of the femur to the medial tibia through the medial meniscus. Prevents: Medially directed shear forces (valgus) Rotational forces

Ligaments continued Lateral collateral ligament (LCL) connects from the lateral condyle of the femur to the head of the fibula. Prevents: Laterally directed shear forces (Varus) External rotation of the tibia

Ligaments continued Arcuate-popliteal complex composed of the semimembranosus tendon and the popliteal ligament connects the lateral condyle of the femur to the head of the fibula. Prevents: Anterior displacement of the tibia relative to the femur. Hyperextension of the knee Hyperflexion of the knee

Patellofemoral joint Triangular bone (Patella) rests between the femoral condyle to form the patellofemoral joint. Three distinct facets Increases angle of pull on the patellar tendon Glides between the femoral Trochlear groove

Patellofemoral joint cont. Greatest compressive forces occur when the knee is in 30 deg. Of flexion. Patellar positioning is maintained by: Lateral retinaculum Medial retinaculum Medial patellofemoral ligament Lateral patellofemoral ligament

Muscles of the Knee Rectus femoris (ext) Vastus lateralis (ext) Vastus intermedius (ext) Vastus medialis (ext) Semitendinosis (flex) Semimembranosus (flx) Biceps femoris (flex) Sartorius (flex) Gracilis (flex) Popliteus (flex) Gastrocnemius (flex) Plantaris (flex)

Nerves L4 L5 S1 S2 S3

Kinematics Flexion primarily carried out by the hamstrings assisted by gastroc, popliteus, gracilis, and sartorius. Secondary responsibility of these muscles is to rotate the tibia Extension primarily carried out by the quadriceps group.

Contusions Fat Pad Contusion Peroneal Nerve Contusion

Bursitis Prepatellar Deep infrapatellar bursitis Pes anserine bursitis Tibial collateral bursitis

Ligamentous Injuries Straight valgus Straight varus Straight anterior Straight posterior Anteromedial rotary Anterolateral rotary Posteromedial rotary Posteroladeral rotary

Knee Dislocations

Meniscal Injuries Longitudinal Bucket-handle Horizontal Parrot-beak

Patellar and Related injuries Patellofemoral stress syndrome Chondromalacia Patellae Patellar Instability and Dislocations Patella Plica Syndrome Patellar Tendinitis Osgood-Schlatter Disease Sinding-Larsen-Johansson’s Disease Extensor Tendon Rupture

IT Band Friction Syndrome

Fractures Avulsion Epiphyseal and Apophyseal Tibial Tubercle Distal Femoral Epiphyseal Stress Fractures Chondral and Osteochondral Fractures Osteochondritis Dissecans Patellar Fractures