Anatomy of the knee

Due to the forces placed upon the knee and its various structures throughout life, the knee is a common site for pain and injury. The knee is the largest weight bearing joint in the body. The forces it is exposed to in walking, bending, running and everyday life predisposes the numerous structures that make up the knee to acute, overuse and degenerative injuries. Some of these are part of the normal ageing process but some require attention to allow it to function normally.

 
Ryan will provide an overview of the anatomical structures of the knee. The myriad of ligamentous attachments, along with numerous muscles crossing the joint, provide insight into the joint’s complexity. This anatomic complexity is necessary to allow for the elaborate interplay between a very mobile yet stable joint in the body.  
 
The knee joint is formed by…

Due to the forces placed upon the knee and its various structures throughout life, the knee is a common site for pain and injury. The knee is the largest weight bearing joint in the body. The forces it is exposed to in walking, bending, running and everyday life predisposes the numerous structures that make up the knee to acute, overuse and degenerative injuries. Some of these are part of the normal ageing process but some require attention to allow it to function normally.

Ryan will provide an overview of the anatomical structures of the knee. The myriad of ligamentous attachments, along with numerous muscles crossing the joint, provide insight into the joint’s complexity. This anatomic complexity is necessary to allow for the elaborate interplay between a very mobile yet stable joint in the body.  
 
The knee joint is formed by the bottom of the femur (thigh bone) and the top of the tibia (shin bone). The patella (knee cap) sits in a groove within the base of the femur and forms a distinctive secondary joint within the one joint capsule. The Patellofemoral joint is subject to compressive load forces with daily activities and takes 50% of the bodyweight whilst walking, 5 times the bodyweight when descending stairs, 7 times the bodyweight when jogging, and 20 times the bodyweight with deep squatting.
Each of the three bones in the knee joint are covered with articular cartilage, which is a tough elastic material, that acts as a shock absorber and allows the knee joint to move with ease. Another cartilage tissue called the meniscus separates the femur and tibia. The meniscus is divided into two crescent shaped discs located on the medial and lateral sides of the knee. This cartilage also acts as a shock absorber, as well as enhancing stability. Due to the forces placed upon the knee, the meniscii can tear either traumatically or over time due to degenerative changes.
 
The joint capsule is a thick ligamentous structure that surrounds the entire knee. Inside this capsule is a specialised membrane known as the synovial membrane that provides nourishment to all the surrounding structures. The synovial membrane produces synovial fluid which lubricates the knee joint. Other structures include the infrapatellar fat pad and numerous bursa which function as cushions to exterior forces and frictions on the knee.
 
The stability of the knee is due mainly to four ligaments. A ligament is a collection of large fibrous bands of tissue, comparable to that of a rope, and connects bone to bone. The ligaments that connect the femur to the tibia and fibula are as follows: medial collateral ligament (MCL) which provides stability to the inner (medial) aspect of the knee; lateral collateral ligament (LCL) providing stability to the outer (lateral) aspect of the knee; anterior cruciate ligament (ACL), in the centre of the knee, limits rotation and forward movement of the tibia; and the posterior cruciate ligament (PCL), also in the centre of the knee, and like the ACL secondarily limits rotation, while primarily limits backward movement of the tibia. The ACL is the main passive constraint of the knee and when ruptured or torn significantly requires surgical reconstruction and a subsequent rigorous rehabilitation program.
 
The two main muscle groups of the knee joint are the quadriceps and the hamstrings. Both play a vital role in moving and stabilising the knee joint. The quadriceps muscle group is made up of four different individual muscles which join together forming the quadriceps tendon. This thick tendon connects the muscle to the patella which in turn connects to the tibia via the patella tendon. Contraction of the quadriceps pulls the patella upwards and straightens the knee. The hamstring muscles at the back of the thigh function in flexing or bending the knee as well as providing stability on either side of the joint line. Additionally the gastrocnemius, the larger and more superficial of the calf muscle group, attaches to the rear surface of the knee contributing to the structure and function of the joint. Swelling within the knee joint can extend out between the two heads of the gastrocnemius and is commonly known as a Baker’s cyst.
 
Should you have any ongoing issues with your knees or have recently sustained an injury to the area, then please call the team at SquareOne Physiotherapy for an appointment with one of our expert Physiotherapists.