The knee Lecture 8

Knee joint The knee joint is the largest synovial joint in the body. It consists of: the articulation between the femur and tibia, which is weight bearing; the articulation between the patella and the femur,

The femur The distal end of femur is characterized by two large condyles, which articulate with the proximal head of the tibia. The condyles are separated posteriorly by an intercondylar fossa and are joined anteriorlly where they articulate with the patella. There are bony elevations on the nonarticular outer surfaces of the condyles - lateral and medial epicondiles, which serve for attachment of collateral ligaments of the knee joint.

Proximal end of tibia The proximal end of the tibia is expanded in the transverse plane for weight bearing. consists of: 1- medial condyle 2- lateral condyle. Tibial plateau is the articular surface of proximal tibia which has 2 articular fossa and intercondylar eminence that has medial and lateral intercondylar tubercles. Inferior to the condyles on the proximal part of the shaft is a large tibial tuberosity and roughened area for muscle and ligament attachment. On the posterior surface of it is a soleal line.

Proximal end of the fibula The fibula is the lateral bone of the leg and does not take part in formation of the knee joint or in weightbearing. It is much smaller than the tibia and has a small proximal head, a narrow neck, and shaft, which ends as the lateral malleolus at the ankle. Head Neck Shaft

Patella The patella (knee cap) is the largest sesamoid bone in the body and is formed within the tendon of the quadriceps femoris muscle. The patella is triangular: its apex is pointed inferiorly for attachment to the patellar ligament, which connects the patella to the tibia; its base is broad and thick for the attachment of the quadriceps femoris muscle from above; its posterior surface articulates with the femur and has medial and lateral facets for articulation.

Articular surfaces The articular surfaces of the bones that contribute to the knee joint are covered by hyaline cartilage. The major surfaces involved include: the two femoral condyles; the adjacent surfaces of the superior aspect of the tibial condyles. The articular surfaces between the femur and patella are the V-shaped trench on the anterior surface of the distal end of the femur.

Menisci There are two menisci, which are C-shaped cartilages, in the knee joint, one medial (medial meniscus) and the other lateral (lateral meniscus). Both are attached at each end to facets in the intercondylar region of the tibial plateau. The menisci are interconnected anteriorly by a transverse ligament of the knee. The lateral meniscus is also connected to the tendon of the popliteus muscle, which pass between this meniscus and the capsule to insert on the femur.

Synovial membrane The synovial membrane of the knee joint attaches to the margins of the articular surfaces and to the superior and inferior outer margins of the menisci. The two cruciate ligaments, which attach in the intercondylar region or eminence of the tibia below and the intercondylar fossa of the femur above are outside the articular cavity, but enclosed within the fibrous membrane of the knee joint.

Cruciate ligaments The two cruciate ligaments are termed 'cruciate' because they cross each other in the sagittal plane between their femoral and tibial attachments: the anterior cruciate ligament attaches to a facet on the anterior part of the intercondylar area of the tibia and ascends posteriorly to attach to a facet at the back of the lateral wall of the intercondylar fossa of the femur; the posterior cruciate ligament attaches to the posterior aspect of the intercondylar area of the tibia and ascends anteriorly to attach to the medial wall of the intercondylar fossa of the femur.

subcutanous prepatellar bursa; deep infra-patellar bursae; knee joint bursas The synovial membrane of the knee joint forms sacs in two locations to provide low friction surfaces: subpopliteal recess (lies between the lateral meniscus and the tendon of the popliteus muscle); suprapatellar bursa (between the distal end of the shaft of femur and the quadriceps femoris muscle). Other bursae include: subcutanous prepatellar bursa; deep infra-patellar bursae; subcutaneous or superficial infra-patellar bursae; and numerous other bursae associated with tendons and ligaments around the joint. recess : طَـيـّة

Fibrous membrane The fibrous membrane of the knee joint is extensive , partly formed and reinforced by ligaments and extensions from tendons of the surrounding muscles. on the medial side of the knee joint, the fibrous membrane blends with the tibial collateral ligament and is attached to the medial meniscus; laterally, the external surface of the fibrous membrane is separated by a space from the fibular collateral ligament and the internal surface of the fibrous membrane is not attached to the lateral meniscus.

Fibrous membrane anteriorly, the fibrous membrane is attached to the margins of the patella where it is reinforced with the vastus lateralis, vastus medialis ,the quadriceps femoris tendons and patellar ligament. Posteromedially, the fibrous membrane is reinforced by semimembranosus tendon and the oblique popliteal ligament.

Ligaments of the knee 1. Patellar ligament It is basically the continuation of the quadriceps femoris tendon inferior to the patella. It is attached above to the margins and apex of the patella and below to the tibial tuberosity. 2. Collateral ligaments: fibular collateral ligament (lateral femoral epicondyle -fibular head); tibial collateral ligament (medial femoral epicondyle -medial margin and medial surface of the tibia). The collateral ligaments, one on each side of the joint, stabilize the hinge-like motion of the knee