Knee Joint

Objectives Name and identify the bony features of the tibia and fibula. Know the type and formation of knee joint. Explain the stability factors of the knee joint. Identify the muscles that act at the knee joint. Know the locking and unlocking mechanism of the knee joint. Understand the functions of the Popliteus and Iliotiabial tract.

Anterior Posterior Transverse condyles epicondyles intercondylar notch patella tibial tuberosity tibial plateaus

Anterior. Patella articulates with the femur. Sagittal section thru knee Tibia: Condyles (plateaus) Tibial tuberosity Tibia and fibula are united by an interosseous Membrane. [Proximal and distal tibio-fibular jts] The fibula is not part of the knee joint. Head of Fibula Patella articulates with the femur. interosseous membrane

During the entire range of knee flexion, the patella only articulates with the femur. KNEE: Modified hinge jt. -flexion / extension (some rotation)

Superior view of tibial surface. Tibial Condyles Tibial Condyles Medial and lateral articular surfaces, separated by an intercondylar eminence. Medial and lateral Menisci: Fibrocartilage shock-absorbers that sit on surface of tibial condyles and deepen the articular surface. Anterior and posterior Cruciate ligaments (ACL, PCL): -hold femur and tibia together -stabilize knee joint lateral articular surface medial articular surface intercondylar eminence lateral meniscus PCL medial meniscus ACL

tibia at their ends (horns), and outer periphery (coronary lig.) Medial and lateral femoral condyles have same shape as corresponding tibial condyles: Medial – elongated Lateral – circular Meniscii: Each is attached to tibia at their ends (horns), and outer periphery (coronary lig.) Femur

Type & Articular Surfaces Knee joint is formed of: Three bones. Three articulations. Femoro-tibial articulation: between the 2 femoral condyles & upper surfaces of the 2 tibial condyles (Type: synovial, modified hinge). Femoro-patellar articulation: between posterior surface of patella & patellar surface of femur (Type: synovial, plane).

Capsule Deficient anteriorly & is replaced by: quadriceps femoris tendon, patella & ligamentum patellae. Possesses 2 openings: one (posteriorly) for popliteus tendon & one (anteriorly) for communication with suprapatellar bursa.

Menisci They are 2 C-shaped plates of fibro-cartilage attached by anterior & posterior horns, to the articular surface of tibia. FUNCTION: Deepen articular surfaces of tibial condyles. Serve as cushions between tibia & femur.

Lateral meniscus Medial Size small Large Shape Circular Oval Outer border separated from lateral collateral ligament by popliteal tendon. attached to the capsule & medial collateral ligament. Mobility More mobile Less mobile Liablity for injury Less liable More liable

The synovial membrane 1- lines the capsule, 2- attaches to the margins of the articular surfaces, 3- attaches to the peripheral edges of the menisci (semilunar cartilages), 4- covers the front of the ant. cruciate ligament, and the back of posterior cruciate ligament. 5- communicates with: - suprapatellar bursa, - popliteus bursa, - semimembranosus burse, - gastrocnemius bursa.

Bursae Related to Knee Suprapatellar bursa: between femur & quadriceps tendon, communicates with synovial membrane of knee joint Prepatellar bursa: between patella & skin. Deep infrapatellar bursa: between tibia & ligamentum patella. Subcutaneous infrapatellar bursa: between tibial tuberosity & skin. Popliteal bursa: between popliteus tendon & capsule, communicates with synovial membrane of knee joint. 1 2 5 3 4

Working on hands-and-knees: Housemaid knee bursa subcutaneus prepatellar bursitis.

Ligaments: 4 Extracapsular 3 1 2 Ligamentum patellae (patellar ligament): from patella to tibial tuberosity. Medial (tibial) collateral ligament: from medial epicondyle of femur to upper part of medial surface of tibia (firmly attached to medial meniscus). Lateral (fibular) collateral ligament: from lateral epicondyle of femur to head of fibula (separated from lateral meniscus by popliteus tendon). Oblique popliteal ligament: extension of semimembranosus tendon.

Ligaments: 2 Intracapsular The Cruciate Ligaments Two in number, situated in the middle of the joint. They are called cruciate because they cross each other Have received the names anterior and posterior, from the position of their attachments to the tibia.

Anterior cruciate ligament: Extends from anterior part of intercondylar area of tibia to posterior part of lateral condyle of femur. Prevents posterior displacement of femur on tibia. Prevents hyperextension. Weaker of the two, slack when knee is flexed & tightens in extension. Posterior cruciate ligament: Extends from posterior part of intercondylar area of tibia to anterior part of medial condyle of femur. Tightens during flexion of knee joint Prevents anterior displacement of femur on tibia.

Stabilization of the medial knee: Tibial collateral ligament. A flat strap which is attached to the medial aspect of tibia and medial femoral epicondyle. Its deeper fibres are attached to the medial meniscus. tibial collateral ligament Joint capsule Retinacular fibres Pes anserinus (goose’s foot): Common insertion of Sartorius, gracilis, semitendinosus

Movements FLEXION: EXTENSION: Mainly by hamstring muscles: biceps femoris , semitendinosus & semimembranosus. Assisted by sartorius , gracilis & popliteus. EXTENSION: Quadriceps femoris. ACTIVE ROTATION (PERFORMED WHEN KNEE IS FLEXED): A) MEDIAL ROTATION: Mainly by semitendinosus & semimembranosus. Assisted by sartorius & gracilis. B) LATERAL ROTATION: Biceps femoris.

Movements INACTIVE (DEPENDANT) ROTATION: A) LOCKING OF KNEE: Lateral rotation of tibia, at the end of extension Results mainly by tension of anterior cruciate ligament. In locked knee, all ligaments become tight. B) UNLOCKING OF KNEE: Medial rotation of tibia, at the beginning of flexion. Performed by popliteus to relax ligaments & allow easy flexion.

Anterior knee in extension Fibrous capsule of the KNEE (anterior): Stabilized by: Extensor Retinacula - Derived from insertions of vastus lateralis and vastis medialis into patella and into sides of patellar ligament. Vastus lateralis Vastus medialis extensor retinacula Patellar Ligament

Posterior knee in extension Fibrous capsule of the KNEE (posterior): Thickened by ligaments: -Arcuate popliteal ligament (arching over popliteus muscle) -Oblique popliteal ligament (from tendon of insertion of semimembranosus m.) arcuate politeal ligament Tendon of Semimembranosus oblique popliteal ligament Popliteus

Structures inside the Knee joint: 1- The 2 menisci (semilunar cartilages). 2- The cruciate ligaments. 3- Popliteus tendon. Nerve supply of the knee joint: Femoral, obturator, tibial, and common pernoneal nerves. Arterial supply of From the anastomosis around knee.

Q-Angle The Q-angle is the angle formed by : 1-a line from the anterior superior iliac spine to the middle of the patella ,and 2-a line from the middle of the patella to the tibial tuberosity. Males typically have Q-angles between 10 to 14o, females between 15-17o.

Atypical Q-angles bowleggedness knock-knees