Tibio/Patellofemoral Joint (Knee)
This page (because of the functionality of the knee) discusses/combines both the Tibiofemoral Joint and the Patellofemoral Joint.

Bones: The tibia which is the shin bone of the lower leg, the patella which is knee cap, and the femur (long bone of the thigh).

Cartilage: There is an articular coverage of cartilage at the end of the tibia and the femur. At the top of the tibia is two crescent shaped meniscus that help keep the rounded end of the femur in place (make a groove for the joint to bend at). Sealing the joint is a a joint capsule that is then covered by a bursa which is a fluid filled lubricating sac to help the joint bend smoothly.

Ligaments:

• On the outside of the knee there is a Medial collateral ligament which runs from the side of the femur to the side of the tibia.
• On the inside of the knee there is a minor Lateral collateral ligament which runs from the inside of the femur to the fibula.
• On the knee is a Patellar ligament which runs from the patella to the tibia.
• Between the femur and the tibia (surrounded by all the cartilage) is the Anterior and Posterior cruciate ligament which makes a small X between the two to help support the knee in rotational stress.

Fat: Below the kneecap and under the Patellar ligaments is a Infrapatellar fat pad. This fat pad is thought to help with cushioning the joint, may play a role in the biomechanics of the knee, or act as a store for repair cells after injury.

Tendons: Some of the important tendons around the knee are the quadriceps tendon which covers about two inches above the knee. The hamstring tendon which several inches on the outside of the knee closer to the back of the tibia. And the iliotibial band which runs from the the ilium of the hip to the front outside of the tibia, this is a tendon band that several muscles of the thigh attach to such as the glutes, tensor fascia latte that help move the knee as well through this band.

Muscles: There are 14 muscles that act on the knee some of them only minorly. The two most influential groups being the quadriceps and the hamstrings. The quadriceps is a group of four muscles on the top of the thigh, the vastus lateralis, vastus intermedius, vastus medialis, and rectus femoris, all of which influential in extending the lower leg away from the body. The hamstrings is a group of three muscles on the back of the thigh consisting of the semitendinosus, the semimembranosus, and the bicep femoris all of which are majorly influential in flexing the lower leg and bringing it closer to the body.

Mechanics: The entire leg is a well developed appendage with muscle attachments that span multiple bones and yet still impact the movements of ones they pass. This means that there are many muscles to continue moving the joint even if injury occurs the the appendage. In contrast because of the muscles interconnectedness with tendons, high impact damage to the leg can cause pain to multiple muscles, ligaments, and tendons.

Range of motion: From having the entire leg straight the lower leg is able to flex backwards to about 155 degrees. This puts the calf muscle right up against the hamstrings. The joint is able to rotate inwards or outwards in reference to the front of the shin about 25 degrees in each direction.

Manipulation:

• The knee makes a nice target for a low side or scoop kick right to the knee cap which with enough power can do heavy damage breaking the patella as well as other damage.
• A round or shin strike to the inside or the outside of the knee can do a lot of damage to the fairly thing ligaments holding the bones together.
• Some upper body locking maneuvers involve pushing the side of the knee to twist the foot outward and fell the opponent.
• In grappling styles there are locks similar to an armbar where the knee is hyper extended.

Usage: Besides obvious body movement mechanics the knee can be used as a striking surface.

• There are a number of knee strikes including upward, forwards, downwards, flying, side, diagonal ect.
• Preferably the center of the patella bone, this way there are no ligaments or tendons at risk, though high impact can damage the patella.
• The very end of the femur can be used just beneath the tendon, though if off slightly can cause muscle pain.
• The top of the tibia and the front of the shin make great striking surfaces of the joint.

Stretching: When most people want to stretch their legs they find that the tendons and muscles around their knees hurt as well, this is because some muscles that affect the knee run for example from the pubis to the tibia passing over the femur, therefore trying to stretch the hip will also affect the knee. For this reason it is important to not bend the knee of the stretching leg and only stretch as far as you can keep the knee locked.

Injury: Very common in high impact sports is turning sharply where the femur and the tibia rotate in opposite directions and are likely to rip the meniscus of the knee.

Pain: Detailing important knee problems with the location of pain.

• Above the knee cap is likely to be swelling / damage to the tendon of the quadriceps.
• Behind the knee is likely to be a Baker's cyst, which is a fluid filled sac that creates pressure due to damaged cartilage, impact, or arthritis.
• Inside or outside of knee could be from a torn meniscus, damaged ligaments, or arthritis.
• On the knee cap is likely to be chrondromalacia which is degeneration of the cartilage of the knee due to poor knee cap alignment, bursitis which is an inflammation of the bursa of the knee, or arthritis.
• Below the knee cap is likely Osgood-Schlatter disease is a lump below the knee which is common in young kids doing high impact sports while undergoing growth spurts, and the body has a hard time healing the injury and growing the body.

Note: These are only common problems to be aware of, if you experience knee pain please consult a physician.

For information on additional joints please refer back to the Joints page.

References

1. Evaluation and treatment of disorders of the infrapatellar fat pad. http://www.ncbi.nlm.nih.gov/pubmed/22149697