The Knee Joint
The knee is the largest, most complex joint, and the most vulnerable to injury in the lower limb. Mostly, the knees are ignored until something causes pain. All these structures around the knee joint are vulnerable to damage. Knee injury is common to all people regardless of age, but athletes and those active in sports are at higher vulnerability. The vulnerability of knee to injuries believe to be as a result it’s function -supports almost the entire body weight. Knee injuries vary from acute and chronic especially in cases of disorders which develop gradually.
Anatomy of the Knee
The knee is made up of four bones. The femur which is the largest of the four bones comes from the upper limb. The femur is attached by capsule and ligaments to tibia. Fibula runs parallel to the tibia. Fibula is located below and next to tibia. Patella, a bone commonly known as knee cap rides on knee joint especially when the knee bends. When a knee moves, it flexes and extend and during the motion, a slight rotational component is made. The knee joint is composed of ligaments which stabilizes the joint, the bones support the knee joint, and gives the joint a rigid structure. The knee is surrounded by muscles in the front -quadriceps and on the back – hamstrings. The muscles facilitate moving of the knee. Cartilage is also found within the knee joint. The meniscus which is C-shaped and usually found in the joint between femur and tibia. Meniscus protects the joint, and enhance free sliding of the bones over each other when moving. Meniscus lubricates and feeds the knee.
It acts as spacer between femur and tibia, an act which reduces friction , and facilitate the diffusion of the joint fluid which carries nutrients into articular cartilage -tissue covering the ends of the bones. Bursa, a fluid sac around the knee joint facilitates free sliding of tendons and muscles as the knee moves. The knee is supplied by femoral artery, and popliteal artery which form a knee work around the knee. The network formed has six branches namely the superior and inferior medial arteries, which are capable of penetrating the knee joint, superior and inferior lateral genicular artery, descending genicular artery, and recurrent branch of the anterior tibial artery. Meniscus is composed of fobriocartilage, and is usually located at the joint’s periphery. Meniscus have no or little supply of blood. The biconcave C-shaped tissues are adapted to lower and manage the stress in the articular cartilage (EMF,1966, pp.308).
At the center of the knee, there are two cruciate ligaments, the anterior and posterior ligaments. The two ligaments are the major stabilizers of the knee. The posterior ligament ensures that femur is held constant preventing it from sliding forwards to the tibia, and tibia from sliding backwards to the femur. The anterior cruciate ligaments ensures the femur does not slide backwards to tibia, and the tibia does not slide forward to femur. The two ligaments functions in a rotational function, meaning that when one of the ligament is damaged, there will be foot instability, especially when the pivoting the injured extremity. Tendons acts as strong tissue cables that connect muscles to bones. Knee tendons include the quadriceps tendon and the patella tendon. Quadriceps tendon connects to the kneecap and allows leg extension. The patella tendon connects to the bottom of kneecap and attaches to the top of the tibia (Al-Turaiki,1996).
When in sports, walking running or doing any type of exercise, pressure is placed on the. The amount of pressure depends with the activity. Walking places less pressure as compared to running, sports other strenuous activities. When twisting forces are placed in the knee, chances of cartilage or ligament tear increases. The anterior cruciate ligament is more vulnerable to as it tears with rapid change in direction when an individual engages in violent twisting motions such as running. When the knee is forced to extend beyond the range it usually extends, the anterior cruciate tears, and cause damages to other structures. The structure of the knee is composed of many delicate and sensitive structures which are closely arranged, to surround or cover each other. this means that when one structure is damaged, it damages one or more of the surrounding or close structure intensifying the knee injury, and reducing the knee from effective functioning. For example when the knee is forced inwards and twists at the same time, medial collateral, medial meniscus and anterior cruciate ligaments tears causing unhappy triad. Poor or lack of blood supply to the meniscus means that when the knee cartilage is damages it is limited to the normal healing process which occurs in other body organs.
With an understanding of what a knee is and it’s constituent, one can easily understand what a knee injury is. Since it is formed by many organs and structure, injury to either of the organ or structure means failure of the entire knee, since every structure is equally important and useful for effective functioning of the knee. Knees are injured as a result of overuse – especially in sports ans exercises where the joint is used continually until it is overworked, as a result of sudden twists and stops or direct blow of the knee (Smith et al.1996).
Torn ligament causes sprain. Ligaments connect bones or cartilage to bones. Every normal knee has four ligaments which collectively connects the femur to the tibia and keep and stabilizes the legs. MCL connects femur to tibia while maintaining the stability of the knee’s inner parts and controls the s knee’s sideway motion. The ACL connects the two bones at the center of the knee, while controlling the rotation and forward motion of the knee (Neumann, 2002, pp. 452).
When ACL and or MCL are damaged, a common sprain occurs. The sprain can also involve complete tear the knee ligaments. A knee with a sprain makes snapping or popping sound at the time of injury, pains from within the knee, especially when the knee is moved, the individual with sprain on the knee can not put any weight on the leg with injured knee, the knee swell, and the person with injure knee feels loose or unstable. When the knee is examined closely, fluid is found collected on the knee caps. A person with a sprain gets problems in his or her attempts to stand, due to damage on the ligament. The bones stability is reduced because the damaged ACL limits the connection of femur to tibia at the center of the the knee, encouraging forward motion and rotation. When the MCL is injured, the connection of femur to tibia inside the knee is limited, increasing sideway movement of the bones. When the bones of the knee are not held in a stable position, the ankle and feet are affected since tibia connects the foot and ankle to the upper limb, and the entire body (Radin et al.2000, 402).
Strain occur as a result of of complete or partial tear of knee muscles or tendons. Quadriceps muscle facilitates straightening and extending of leg, while the hamstring facilitates bending of knee. With a strain on the knee the injured individual is unable to straighten the leg, can not extend the leg, and the knee fails to bend. The knee fails to support the weight of the injured person the person gets difficulties in attempts to stand or walk. The knee swells and become painful, and gets bruises limiting the ability of the knee to support the body weight, and fail to effectively connect the foot and ankle to the body (McPoil et al. 2001, pp. 313).
The cartilage in the knee joint is capable of softening especially in cases of injury, muscle overuse,or continuous rubbing of patella and thighbone. The condition is characterized by ache and pain when walking. Femur and tibia can also break off, a condition which causes long-term knee pain. The condition is characterized by swelling, the leg fails to extend, becomes stiff, and produces popping sensations when the knee is moved.
In most cases, meniscus is damaged in sports especially when there is sudden changes in speed and sideways movements which increases the risk of menisci tear. Menisci injuries can occur solely or can occur together with ACL tear. The condition is characterized by swelling of front part of the knee, the knee becomes tight, tender and in few cases produces effusion. Meniscus wears out or rather deteriorates with age, meaning that as one ages, the cartilage develops degenerative tears. When meniscus is damaged, the torn pieces are left in the joint, and keep moving inside the joint in an abnormal fashion. Since the space occupied by the knee joint is small, and the many structures within the joints, fragments of damages meniscus gets limited spaces to enable constant movement, so as the damages increases, the fragments build up, and accumulate between femur and tibia, where they are continually held. Occurrence and holding of meniscus fragments, between femur and tibia bones makes the knee to swell, unable to move, and painful. A consistence maintenance of articular cartilage integrity prevents development of degenerative or post-traumatic arthritis (Nordin et al. 2001, pp.190).
When knee tendons are overworked, or rather overused chances of knee inflammation and irritation increases. The condition is characterized by tenderness of the knee, and pain when walking or moving the leg.
Functions of the Knee
The complex structures and organs within a knee helps the knee to perform many functions. Although a human knee has a number of functions, the vary with situations and activities. For example a person is is activities in sports will use the knees in a different way to a person who do not engage in sport. However in general cases the knees are adapted to provide stability when bearing weight, ensure leg mobility in the space, support the body, connect the lower leg and to the body and to transmit loads from the body to the lower leg. Some of these functions are not recognized until the knee is injured. For example many people do not consider the knee to have any role in human posture, but when the knee is injured especially the ligaments, connection of tibia t-o femur for normal posture fails, and it becomes hard for injure person to stand. People with injured knees especially ones with chronic knee disorders such as arthritis tends to walk in a bent posture as a way of distributing their body weight leaving small weight for the knee to stabilize (Logan ; Lindsay,1994).
A functional knee facilitates free leg mobility in the space. The muscles, tendons, ligaments and other structures within the knee joint coordinates to allow the knee to bend and rotate. The bending and rotating of the knee allows and supports the leg as it move in any direction in the space. When any of the joint’s structure is injured, the mobility is the leg is limited.
In normal circumstances when the body, or the thigh is subjected to heavy loads, the knees transmit the load from the loaded part of the body, to the lower leg. This helps in distributing the pressure exerted in the region with the load enabling the body to handle the weight of the load as it becomes lighter. An individual with injured or diseases knee can not hold the pressure exerted by the load since the knee can not facilitate distribution of the load to the lower legs to reduce the weight.
Human knee joints are compose of many structures and organs. When one of the structure is damaged or injured other structures or or the entire knee is affected, and is limited to it’s functions. Every individual should ensure healthy knees for their effective functioning. This can be achieve through protecting the knees especially during sports. When jumping, they should bend their knees when landing to reduce pressure in ACL, always bend at hips and knees to prevent ligament injury.
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