Pain in the back of the knee can be of concern, especially when it interferes with our daily activities. This article explains the complex anatomy of the knee and gives possible causes for posterior knee pain.
If you are concerned about pain in the back of your knee, then call OrthoNeuro to book an appointment with one of our orthopedic surgeons. You can find us throughout Columbus, Ohio.
Pain behind the knee (also known as posterior knee pain) can have many different etiologies (causes) due to the complex make-up and larger number of structures within the knee joint. Pain can be due to damaged bones, cartilage, ligaments, nerves, or vasculature.
Posterior knee pain can develop after an injury, or it can gradually advance over time due to wear and tear. Having a thorough understanding of the anatomy of the knee joint can help direct physicians as to the best possible treatment.
The knee joint is the largest joint within the human body and is crucial for movement and maintaining balance. The knee joint is a synovial hinge joint composed of muscles, bones, cartilage, ligaments, nerves, arteries, and veins.
A synovial joint is a type of joint that is surrounded by a membrane that secretes a thick, lubricating fluid known as synovial fluid. Healthy synovial fluid within the knee allows for smooth movement of all the components and reduced friction and irritation in everyday movement.
Dysfunction of the synovial fluid and joint capsule can be a common cause of posterior knee pain. The fluid can fill spaces or other sacs (bursae) surrounding the knee in which it is not supposed to and can cause inflammation, pain, and swelling.
The hamstrings and gastrocnemius (calf muscle) are the two groups of muscles that interact with the posterior aspect of the knee.
The hamstrings are located on the back of the thigh, and help flex the knee and extend the hip. They are composed of three muscles: the biceps femoris, semimembranosus, and semitendinosus.
The biceps femoris connects to the outside of the tibia, which the semimembranosus and semitendinosus attach to the inside of the tibia. These three muscles connect to the tibia via strong tendons that can become inflamed, resulting in pain in the back of the knee.
The three bones that come together to form the knee joint are the femur (thigh bone), tibia (shin bone), and patella (kneecap).
These bones form two different articular surfaces (junctions where two structures meet each other) within the joint: the tibiofemoral (tibia and femur) joint and the patellofemoral (patella and femur) joint. This can be a common site of wear and tear.
These bones all work together to provide structural support and allow for muscles to pull on them to provide movement.
Ligaments are strong, fibrous connective tissues that connect bone to bone. Four major ligaments keep the knee stable: the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), lateral collateral ligament (LCL), and medial collateral ligament (MCL).
The four ligaments work in conjunction to resist unwanted movement of the femur and tibia. The ACL and PCL work together to resist any anterior (forward) and posterior (backward) movement of the tibia. The ACL prevents the tibia from moving forward, while the PCL prevents the tibia from moving backward.
The MCL and LCL work in a pair similar to the ALC and PCL; however, they resist the side-to-side movement of the joint. The MCL runs along the medial (inside) aspect of the knee and keeps the knee from taking on a valgus (“knock knee”) appearance. The LCL runs along the lateral (outside) aspect of the knee and keeps the knee from taking on a varus (“bow-legged”) appearance.
The ligaments’ role in keeping the knee properly aligned is crucial for maintaining a healthy joint.
Fibrocartilage and hyaline cartilage are two types of cartilage in the knee. The meniscus is the major fibrocartilage within the knee and is located within the space between the femur and tibia. It is a wedge-shaped cartilage whose role is to act as a shock absorber for the joint.
Hyaline cartilage is another type of cartilage in the knee. It lines the ends of the bones and helps protect them as they move within the joint.
There could be several reasons why you might experience pain behind the knee. Some of the possible causes of posterior knee pain include the following:
Popliteal cysts (Baker Cysts) are abnormal fluid collections in the posterior aspect of the knee. When there is excess fluid in the knee, it tends to drain towards the posterior aspect. This pooling of fluid is known as a Baker’s Cyst.
The increase in fluid in the area can cause discomfort and swelling, which can be alleviated with rest and NSAIDs (Non-steroidal anti-Inflammatory drugs)
Osteoarthritis is the most common form of arthritis and is caused by the breakdown of the hyaline cartilage. This breakdown no longer protects the bones within the joint, and the joint becomes inflamed.
Usually, pain and inflammation are improved with rest and are made worse with activity. Knee joint injection therapy methods can be discussed with your physician to alleviate pain. You and your physician can decide what type of knee injection would be best for your care.
In severe cases of osteoarthritis of the knee, a knee replacement may be the only treatment.
This can be caused by trauma sustained to the knee. Usually, the mechanism of injury is a twisting motion, and a “pop” is felt in the inside/back of the knee. When a portion of the meniscus is torn, it can cause pain and the feeling of instability in the knee.
Because the meniscus is made of cartilage and not bone, it will appear black on an X-ray. MRI is better suited to analyze the extent of the meniscus tear.
Ligamentous tears can be caused by trauma sustained to the knee that causes the ligaments to be overstretched or even rupture completely. Often, these injuries are seen when the knee joint undergoes quick, sudden twisting movements.
After the injury, the knee may become unstable and increase in swelling. This inflammation can build pressure in the knee, and pain and discomfort can be localized to the back of the knee.
In the office, physicians can perform multiple physical examination tests to determine the ligament that is injured. The anterior (Tests ACL) and posterior (Tests PCL) drawer tests can be used for the cruciate ligaments, while the varus (Tests LCL) and valgus (Tests MCL) stress tests can be used for the collateral ligaments.
The MRI can be used to identify which ligaments have been damaged and the extent of the tear.
Damage to the hamstrings and gastrocnemius muscles can be the underlying cause of posterior knee pain. The tendons that connect the muscles to the bones can acquire microtears from overuse or from attempting too strenuous activities too suddenly.
A common treatment for this type of injury is remembered through the abbreviation RICE: Rest, Ice, Compression, and Elevation. RICE gives the tendons time to heal and improve the posterior knee pain. Devices such as walking boots or braces could also be used to relieve the symptoms.
Professional medical advice should be consulted if the pain or discomfort is too severe to complete activities of daily living. If conservative treatments such as rest, ice, heat, and over-the-counter NSAIDs have proven unsatisfactory, it could be time to undergo further imaging studies under the care of an orthopedic team.
Due to the complex structure of the knee, the mechanism of injury and the progression of the symptoms are very important when determining the reason behind the pain. If symptoms have not subsided, please feel free to schedule a consultation with one of our expert physicians at OrthoNeuro.
Our highly trained orthopedic surgeons have a multitude of experience in treating injuries like these. Their goal is to help you return to the activities you need to do daily. Call or book an appointment with us today at one of our locations in Columbus, Ohio!
Medically Reviewed by Mark Gittins, DO
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