The knee joint (also known as the synovial or the tibiofermoral joint) allows the lower leg to move about freely whilst also being able to support the body’s weight, which is no mean anatomical feat! We use our knees to sit down, walk upstairs, stand around chatting and for running marathons (if that’s your thing). If you are unlucky enough to have a problem with your knees, you'll soon realise how much you take them for granted.
The lower leg bone, the tibia, and upper leg bone, the femur, meet at the knee. In between the two is the patella, or kneecap, and its important job is to protect the rest of the knee and to help with how the leg is moved and bent. This is done by the kneecap sliding up and down on a dedicated groove found on the femur. A joint capsule surrounds the knee joint to protect it and offer lubrication and increase strength.
The knee is not just comprised of bone - the joint is also made up from cartilage, muscles, tendons and ligaments.
The cartilage is a tough, rubber like material that acts like a shock absorber. Made primarily up of two layers, the lateral (or outer) meniscus and the medial (or inner) meniscus, with additional articular cartiledge that sits on the ends of the bones. In addition to protecting against impacts, the knee cartilage increases the stability of the joint and prevents the bones from meeting or colliding together during exercise.
Muscles & Tendons
The muscles and tendons move the knee joint via a system where the muscles contract to pull the tendons which are attached to the bone. The hamstrings are used to bend the knee, and to straighten the leg the quadriceps do this by using via the patellar tendon. The knee joint mainly allows for flexion and extension of the leg, along with a small degree of medial and lateral rotation.
The ligaments help to keep the knee join together by stopping it from collapsing or bending the wrong way, whilst resisting the forces that could cause the knee to twist too much. Their job is crucial, so injuries to ligaments (especially to the Anterior Cruciate Ligament in particular) can be a real problem.
There are three other key ligaments besides the Anterior Cruciate Ligament (ACL), which are the Medial Collateral Ligament (MCL), the Lateral Collateral Ligament (LCL) and the Posterior Cruciate Ligament (PCL).
Knee related AnatomyStuff resources:
Budget Flexible Knee Model with Ligaments
Knee Joint Model with Removable Muscles (12 part)
Strengthening the Hip and Knee Chart / Poster - Laminated
Osteoarthritis Knee Model Set (4 stages)
Rheumatoid Arthritis (RA) Knee Model