Knee Joint – Anatomy, Function, and Conditions
Knee Joint Anatomy
Your knee is one of the strongest joints in your body as it must take your whole body’s weight when you move. The knee joint is a “hinge” joint, meaning it mostly bends back and forth in one direction. Your knee muscles are powerful muscles in your thigh that must move your knee back and forth, allowing you to move, run, and jump. To stay in position and absorb the impact of walking and running it contains cartilage, ligaments, and tendons.
The knee is often damaged during sports injuries, as the high impact of direct force to the knee or awkward twists can sprain and tear the knee’s ligaments and cartilage. The knee is also susceptible to wear and tear as you age, so knee arthritis is common.
Your knee joint includes four bones:
- The femur (thigh bone) is the long bone that connects your hip to your knee.
- The patella (kneecap) is the small bone that sits in front of your knee joint, covering and protecting it.
- The tibia (shin bone) is the main bone in your lower leg, connecting your knee to your ankle.
- The fibula (outer shin bone) is the other bone in your lower leg, placed to the side of your tibia.
Your knee joint has two types of cartilage – the articular cartilage and the menisci. Cartilage is the tough elastic tissue that helps your joints move better by absorbing shock and allowing bones to move against each other without causing friction.
Knee Articular Cartilage
Your knee’s articular cartilage, also known as chondral cartilage, lines the surface of all your knee bones, protecting them from wear and tear as the knee joint moves. In knee osteoarthritis, your knee cartilage wears down and movement causes friction in the bones, leading to knee pain and stiffness.
Knee Meniscus Cartilage
The knee menisci are two thick pads of cartilage that sit inside your knee joint and act as shock absorbers to take the impact of walking, running, and landing from jumps. They also help stabilize the knee and reduce friction when you move your knee joint. Meniscus tear is a common condition of your knee meniscus and can occur due to direct impact or sports injury.
Your knee has four key ligaments that help to stabilize the knee and keep the knee bones in position while the knee joint moves.
Anterior Cruciate Ligament (ACL) – Located in the middle of your knee joint, this ligament forms a cross with the posterior cruciate ligament, keeping the femur and the tibia held together. ACL tears are the most common knee ligament injury.
Posterior Cruciate Ligament (PCL) – Also located in the middle of the knee, this ligament works with the anterior cruciate ligament to stop your tibia from moving backwards and becoming unstable.
Medial Collateral Ligament (MCL) – Situated at the inner side of your knee joint, this ligament keeps the medial side of your femur and tibia held together to prevent your knee from buckling inwards.
Lateral Collateral Ligament (LCL) – Located on the outer side of your knee joint, opposite the medial collateral ligament, this ligament holds the lateral side of the femur and fibula together.
The main two muscle groups of your knee are the quadriceps and the hamstrings. There are other muscles in your thigh that help with knee movements, but the bulk of the thigh muscles is made up of these two muscle groups.
The quadriceps are large muscles on the front of your thigh which connect to the patella. When your quadriceps contract it pulls on your patella, which in turn pulls on the tibia via the patellar tendon. This straightens your leg.
The hamstrings are large muscles on the back of your thigh which attach to your tibia and fibula. When your hamstrings contract, it pulls on your tibia and fibula, bending the knee.
More Information | Dr. Pamela Mehta M.D, Knee Surgeon in San Jose
Pamela Mehta, MD – Knee Surgeon in San Jose, California
Dr. Mehta is a knee surgeon and has a special interest in surgery for degenerative joint conditions such as knee arthritis, as well as minimally invasive surgery (arthroscopy) for knee conditions. She can assess your knee pain, diagnose your knee condition, and offer knee surgery if it is required. Dr. Mehta is known for being compassionate and caring with her patients and provides concierge care developing a tailored plan for each patient.