Introduction:
The knee is the largest and most important joint in the body that connects the thigh and the leg. The knee joint supports and stabilizes the body in an upright position. It is a hinge type of joint that plays an essential role in all the movements of the leg. The knee joint consists of a connection between three bones - the femur (thigh bone), the tibia (shin or shank bone), and the patella (knee cap).
What Is a Patella Bone?
The patella, which covers the front aspect of the knee joint, is a thick, flat, triangular bone. In Latin, ‘patella’ refers to a little pan or dish. With a wide concave articular surface in the back and a rough convex surface at the front, the patella bone resembles a pan. It is a tiny, independently moving bone that is ideally formed to prevent damage to the knee. For this reason, it is called the kneecap.
What Type of Bone Is the Patella?
The patella belongs to the group of bones known as sesamoid bones, which are formed like sesame seeds. Embedded in a tendon, it is the biggest sesamoid bone in the body. It is composed of homogeneous, thick cancellous bone tissue, with a thin cortical plate encircling it. The patella continues to be soft cartilage in infants until it begins to change into hard bone tissue between the ages of three and six. The age of puberty marks the completion of this skeletal change.
What Is the Anatomy of the Patella Bone?
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The patella bone is triangular with an apex, base, and front and back surfaces.
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The apex of this triangular bone is pointed and faces downwards. The apex of the patella is attached to the tibia by a ligament called the patellar ligament.
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The base of the triangle forms the upper aspect. The tendon of the quadriceps (thigh muscle at the front) attaches to the base of the patella.
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The back surface of the patella has two planes, namely the medial facet and the lateral facet. The lateral facet is larger and determines the side of the patella bone.
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The third middle surface of the patella contains numerous microscopic canals or channels filled with fatty tissues.
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The patella receives blood from the large network of blood vessels contributed by the tibial and geniculate arteries.
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Quadriceps femoris is a muscle group comprising four major muscles of the thigh and converge into the quadriceps tendon attaching at the top of the patella. They act together for the extension of the leg at the knee joint.
Where Is the Patella Located?
The patella bone is located in front of the knee joint. At its articular surface, the patella articulates with the intercondylar groove of the femur bone, which is called the trochlear groove. The connection between the femur and the patella is known as the patellofemoral joint. It is a complex structure with high functional and biomechanical requirements and is exposed to high compression forces. The smooth white tissue known as articular cartilage covers the back side of the patella and the end of the femur, allowing the bones to move freely and friction-free.
The blood supply to the patella bone is from the genicular arteries (one of the important arteries of the leg, most of which cross-link in the knee region). Additionally, the patellar plexus is a network of tiny nerves located in front of the patella. The skin in and around the knee region receives sensory innervation from these nerves.
What Are the Functions of the Patella Bone?
The patella bone plays a key role in the movement of the knee joint. The following are the actions attributed to the patella bone:
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The main purpose of the patella is to facilitate knee extension, therefore the patellofemoral joint is a hinge-type joint. This joint is important for activities such as walking up stairs, sloping terrain, and extending the knee to stand up from a sitting or lying position. The patella's harmonious interaction with the trochlear groove is essential to the patellofemoral joint's normal function.
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The patella bone protects the front surface of the knee joint from physical injuries.
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It increases the quadriceps muscle's efficiency and is compared to a frictionless pulley.
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Between the femur bone projection and the quadriceps muscle tendon, the patella bone is entirely encased. As such, it lessens the load on the underlying components and serves as a spacer.
What Are the Diseases Associated With the Patella Bone?
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Fracture: The patella is prone to injury or damage due to its position. A fracture in the patellar tendon is known as a patellar fracture. The patient will experience significant pain and swelling. Furthermore, they might not be able to move their legs or walk.
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Patellar Malalignment: Based on the vertical alignment of the patella bone to the femur, the malalignment can be termed as,
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Patella Alta: This condition is caused by the high-riding patella (superiorly aligned to its normal position).
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Patella Baja: This condition is caused by the low-riding patella (inferiorly aligned to its normal position).
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Patellar Instability: Often the patella slips out of its normal position due to any knee injury and results in partial or complete patellar dislocation to the sides. This condition is more common in the young athlete population. Chronic patellar instability can happen in trochlear dysplasia, in which the trochlear groove is anatomically shallow, flat, or convex.
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Patellofemoral Arthritis: This condition is characterized by swelling and tenderness in the patellofemoral joint caused by damage to the articular cartilage.
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Exostosis: Chronic irritation to the patella bone results in extra growth of bone projecting from the existing bone surface. Patellar exostosis is painful and limits knee movements.
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Osteoporosis: Any bone in the human body, including the patella, can be impacted by osteoporosis. Because osteoporosis weakens bones, fractures that occur suddenly and unexpectedly are more likely to occur. Many people are not aware that they have osteoporosis until after it breaks a bone.
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Patellofemoral Pain Syndrome: Another name for patellofemoral pain syndrome (PFPS) is the jumper's knee or runner's knee. Pain underneath or close to the kneecap (patella) is a symptom of this medical disease. One or both of the knees may experience PFPS. Both adults and children are impacted by it.
What Kinds of Testing Are Performed on the Patella?
The patella reflex test is the most often administered test on the patella. Using a special hammer, the doctor will tap the knee directly below the patella. The leg ought to stretch as a result of the abrupt stimulation of the tendons, which sets off an involuntary reflex that is beyond control. This is known as the patellar reflex. This test may be done as part of a standard evaluation by the doctor or if they have reason to believe that there is a problem in the neurological system.
A physician or surgeon may require imaging studies if individuals have had a patellar fracture or injury. These procedures could include:
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Radiography.
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MRI (magnetic resonance imaging).
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CT (computed tomography) scan.
What Are the Typical Patellar Treatments?
Treatment of the patella is usually not necessary unless there is knee pain, an injury, or a fracture. Many disorders affecting the patella can be addressed in the same way, including:
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Using a brace or other form of immobilization.
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Taking a break from or refraining from the behavior that causes harm.
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Physical therapy.
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Remedies used at home, including over-the-counter analgesics.
Conclusion:
The patella is a bony shield that protects the vital and delicate structures of the knee joint. The patellofemoral joint is an integral part of the knee joint that plays an essential role in everyday life. A proper understanding of the normal anatomy and the biomechanics of the patella is necessary to identify diseases in the knee and efficiently plan the treatment protocol.
