Knee Anatomy: Structure, Function, Injury, and Treatment

Anatomy of the Joint

The anatomy of the knee is one of the most fundamental joints that allows for flexion and extension of the leg. Known scientifically as the articulatio genus, it is a complex hinge joint where the femur, tibia, and patella meet. It is specifically a synovial joint, or a joint characterized by a synovial fluid-filled cavity surrounded by a joint capsule that encourages larger movements and stability. This joint acts as a hinge, but has additional rotation associated with it. Two femoral condyles are found on the end of the femur and they lay on the tibia creating the tibial plateau. The patella, or kneecap, lays at the center of the knee and slides in the patellofemoral groove formed by the femoral condyles. 

Anatomy of the Ligaments, Tendons, and Muscles

When it comes to the ligaments and tendons that connect the bones of the knee together, there are four dominant ones. The medial collateral ligament (MCL) and the lateral collateral ligament on either side of the joint connect the bones together. Inside the joint, there exist the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). While the MCL and LCL control the side to side movement of the joint, the ACL and PCL manage the front and back motion. 

Of these ligaments, the ACL is the most crucial. It runs through the center of the knee from the femur to the tibia, preventing the femur sliding backwards onto the tibia. It plays a significant role in stabilizing the knee. Consequently, it may cause instability when damaged if weight is placed on the knee. 

In order to avoid excess tension and friction in the joint, the knee additionally contains the medial and lateral menisci, which are made of fibrous cartilage and act as cushions between the femur and tibia. This helps to provide a better force distribution in the knee. In addition to this cartilage, there exists the articular cartilage that covers most of the bones in the joint and the bursae. This cartilage protects the joint from pressure and friction associated with rubbing, and allows for the bones to glide past each other with ease to facilitate motion.

Around the knee’s bones, ligaments, and menisci, you will find the muscles. The ones worth mentioning include the quadriceps femorus muscle, the hamstring muscles, and the popliteus muscle. These muscles help to strengthen and flex the knee.

Common Injuries of the Knee

It is most often acute abrasions, overuse, and systemic conditions that result in injuries to the knee. 

Acute injuries are caused by sudden, abnormal movement of the knee that places an unendurable amount of stress on the joint. The common acute injuries include: 

• Muscle tension injuries such as sprains or strains. 
• Injuries to the ligaments and tendons, such as an ACL tear. 
• Meniscus tears.  
• Bursae inflammation 
• Broken patella

Overuse injuries are caused by repetitive trauma when an insupportable amount of stress is placed on the knee. Some examples include: 

• Tendinitis 
• Tendinosis 
• Bursitis

Other injuries of the knee can result from preexisting bodily conditions. Common chronic conditions such as arthritis, lupus, and osteomyelitis can cause inflammation and stiffness.

Symptoms of Injuries to the Knee

When the knee undergoes trauma, it is important to seek medical attention in order to maintain the health of your knee and retain proper function. This being said, how do you know if your injury is serious? Below are some general symptoms to look out for. 

• Pain and swelling upon bending the knee or placing weight on the joint may be associated with ligament tears or bone fractures. 
• Feelings of instability and inflammation may indicate overuse or acute injuries. 
• Popping or grinding of the joint may be a sign of cartilage or meniscus tears.

Treatments for Injuries to the Knee

If the bones appear deformed, the pain is unbearable, there is a loss of feeling or numbness, or there exists extreme swelling or inflammation, emergency care should be called for. If the injury is not pressing, use the at-home care treatment ‘RICE’: rest, ice, compression, and elevation of the knee. Anti-inflammatory medications such as Ibuprofen or Naproxen Sodium, as well as knee sleeves or bandages can be used to help with compression and pain.

When undergoing nonsurgical treatment, the doctor will most likely recommend rest, immobilization of the knee with a brace, and physical therapy. In cases where the injury is more severe, such as when osteoarthritis causes breakdown of the cartilage, surgery may be necessary. Interventional and regenerative pain management procedures may also be a route worth considering in moderate to severe cases. 

To best avoid a knee injury, there are a few easy modifications that can be implemented into your daily routine. Most importantly, be sure to stretch before and after strenuous activity, use proper technique and motion during said activity, and know your limits. If you over-train or overstrain your knee joints, you may do more harm than good to your health. By focusing on your technique and form when performing certain activities, you can select the appropriate strength and flexibility exercises to optimize your knee’s movements and maintain proper health and safety.

Written By: Sudheshna Thirunahari

Edited By: Camden Rowe