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    Related Topics

    From Musculoskeletal System

    Pubis
    Part of the pelvis that joins with the opposite side to form the pubic symphysis.
    Parietal Bones
    Bones forming the sides and roof of the skull.
    Humerus
    Upper arm bone connecting the shoulder to the elbow.
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Adductors
    Muscles that bring the thighs toward the midline.
    Sternum
    Breastbone located in the center of the chest.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Ischium
    Part of the pelvis that supports weight while sitting.
    Masseter
    Muscle that elevates the mandible.
    Sesamoid Bones
    e.g., patella, some found in hands/feet.
    Ribs (12 Pairs)
    12 pairs of bones that form the sides of the thoracic cage.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Syndesmoses
    Fibrous joints where bones are connected by ligaments.
    Anterior Longitudinal Ligament
    Spinal ligament running along the front of the vertebral column.
    Brachioradialis
    Muscle responsible for forearm flexion.
    Metatarsals (5 bones)
    5 bones forming the mid-foot.
    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Triceps Brachii
    Muscle responsible for elbow extension.
    Rotator Cuff Muscles
    Supraspinatus, Infraspinatus, Teres Minor, Subscapularis.
    Occipital Bone
    Bone forming the back and base of the skull.
    Saddle Joints
    e.g., thumb joint
    Pivot Joints
    e.g., atlanto-axial joint
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    Scapula
    Shoulder blade providing attachment for muscles of the upper limb.

    Patellar Tendon

    Reviewed by our medical team

    Tendon connecting the patella to the tibia.

    1. Overview

    The patellar tendon (more accurately termed the patellar ligament) is a strong, flat band of connective tissue that connects the inferior pole of the patella (kneecap) to the tibial tuberosity. It plays a vital role in knee extension as part of the quadriceps mechanism. Though commonly called a tendon due to its association with the quadriceps muscle, it is technically a ligament because it connects bone (patella) to bone (tibia).

    2. Location

    The patellar tendon is located in the anterior aspect of the knee:

    • Proximally: Attached to the apex (inferior portion) of the patella.

    • Distally: Inserts onto the tibial tuberosity on the anterior surface of the proximal tibia.

    • Anteriorly: Lies superficial to the infrapatellar fat pad and anterior to the knee joint capsule.

    • Deep to: The skin and superficial fascia of the anterior knee.

    3. Structure

    The patellar tendon is a thick, fibrous band composed primarily of densely packed collagen fibers arranged in parallel:

    • Length: Typically ranges from 3 to 5 cm in adults.

    • Width: Approximately 2 to 3 cm; broader at the patellar end and narrower at the tibial insertion.

    • Histology: Composed of type I collagen, tenocytes, and a small amount of ground substance.

    • Surrounding structures: Covered by a thin paratenon and surrounded by fat pads (prepatellar and infrapatellar fat pads).

    4. Function

    The patellar tendon is an essential structure in the extension mechanism of the knee:

    • Transmits force: Transfers force from the quadriceps muscle (via the patella) to the tibia during knee extension.

    • Supports locomotion: Critical for walking, running, jumping, squatting, and standing from a seated position.

    • Acts as a pulley: Works with the patella to change the angle of force, increasing the mechanical efficiency of the quadriceps.

    5. Physiological role(s)

    Beyond movement, the patellar tendon supports several physiological and biomechanical roles:

    • Joint stabilization: Assists in maintaining proper alignment of the patella and tibia during dynamic motion.

    • Force distribution: Helps evenly distribute loads across the knee joint, reducing stress on cartilage and bone.

    • Reflex arc: Involved in the patellar reflex (knee-jerk reflex), an important neurological test of spinal cord integrity (L2–L4).

    • Protects underlying structures: Shields deeper components of the knee joint during anterior impacts.

    6. Clinical Significance

    The patellar tendon is frequently involved in musculoskeletal conditions, especially among athletes and active individuals:

    • Patellar tendinopathy (jumper’s knee):

      • Chronic overuse injury characterized by pain, inflammation, and degeneration of the tendon, commonly seen in jumping sports (e.g., basketball, volleyball).

    • Patellar tendon rupture:

      • A complete tear that results in loss of active knee extension; often occurs due to sudden, forceful contraction of the quadriceps.

      • Requires surgical repair and long-term rehabilitation.

    • Osgood-Schlatter disease:

      • Common in adolescents; involves traction stress on the tibial tuberosity at the insertion of the patellar tendon, causing pain and inflammation.

    • Patellar tendon graft:

      • Often used in anterior cruciate ligament (ACL) reconstruction surgeries as a reliable autograft source (bone-patellar tendon-bone graft).

    • Tendinitis vs. tendinosis:

      • “Tendinitis” refers to acute inflammation, while “tendinosis” indicates chronic degenerative changes—both affecting function and requiring different treatment approaches.

    Did you know? The tibia is the second largest bone in the body after the femur.