The tibiofemoral joint forms the primary articulation of the knee, connecting the distal end of the femur, or thigh bone, with the proximal end of the tibia, or shin bone. This joint facilitates a wide range of motion while bearing the majority of the body’s weight. It allows for both flexibility and stability. The joint’s integrity is important for everyday activities, from standing and walking to more dynamic movements like running and jumping.
Anatomy of the Joint
The tibiofemoral joint connects the rounded lower ends of the femur, known as the femoral condyles, with the flatter top surface of the tibia, called the tibial plateau. The medial condyle of the femur is larger than its lateral counterpart. These bony surfaces are covered by articular cartilage, a smooth tissue that minimizes friction and allows for fluid movement.
Within the joint, two C-shaped pieces of fibrocartilage, the menisci, are located between the bones. The medial meniscus is on the inner side of the knee, while the lateral meniscus is on the outer side. These menisci serve as shock absorbers, distributing compressive forces across the joint and enhancing its stability by improving the fit between the bone surfaces.
Four main ligaments provide further stability. The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) are inside the joint, crossing each other to prevent excessive forward or backward sliding of the tibia relative to the femur. The medial collateral ligament (MCL) is on the inner side of the knee, resisting inward forces, while the lateral collateral ligament (LCL) is on the outer side, preventing outward forces.
Movement and Function
The tibiofemoral joint operates as a modified hinge joint, enabling flexion and extension. Flexion involves bending the knee, bringing the heel closer to the buttocks, while extension is the act of straightening the leg. These actions are important for activities such as walking, sitting, and standing.
A small degree of rotational movement is also possible at the tibiofemoral joint, specifically internal and external rotation when the knee is flexed. This rotational capacity, though limited, contributes to the knee’s flexibility during complex movements. Beyond its range of motion, the joint’s main function is to support the body’s weight. It absorbs and distributes forces during both static activities like standing and dynamic actions such as running, jumping, and squatting, allowing efficient load transfer.
Common Tibiofemoral Issues
One common degenerative condition affecting the tibiofemoral joint is osteoarthritis, often called “wear and tear” arthritis. This condition involves the gradual breakdown and loss of the articular cartilage covering the ends of the femur and tibia. As the cartilage erodes, the protective space between the bones narrows, leading to increased friction, pain, stiffness, and potentially bone-on-bone contact.
The tibiofemoral joint is also susceptible to acute injuries, particularly affecting its soft tissue structures. Meniscal tears occur from twisting motions of the knee, especially when the foot is planted. Symptoms can include pain, swelling, stiffness, and a sensation of catching or locking within the joint. Ligamentous injuries, such as an anterior cruciate ligament (ACL) tear, are common, particularly in sports involving sudden stops, pivots, or changes in direction. An ACL tear can cause a popping sound, immediate swelling, and a feeling of instability in the knee.