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Knee Joint

Anatomy & Function

Dr. Pamela Mehta, MD

anatomy of the knee bones, cartilage, and ligaments

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.

anatomy of the knee bones, cartilage, and ligaments

Knee Bones

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.
Knee bones include the femur, the patella, the tibia, and the fibula

Knee Cartilage

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.

the knee bones are covered with articular cartilage and also have two meniscus

Knee Ligaments

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.

diagram of knee ligaments including ACL, PCL, MCL, and LCL

Knee Muscles

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.

Book a Consultation with Dr. Pamela Mehta, MD

The Best Orthopedic Surgeon in San Jose

Dr. Mehta is a board-certified orthopedic surgeon who can help you recover from your joint condition.

We can help if you:

Further Information

Learn about the causes of knee pain, what the diagnosis could be, and the treatments available.

Learn about knee surgery, including minimally invasive surgical techniques like knee arthroscopy.

Knee Conditions

Learn about different knee conditions, their symptoms, how they are diagnosed, and what treatment we can offer at Resilience Orthopedics, including: