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    From Musculoskeletal System

    Lumbar Vertebrae (L1 - L5)
    Vertebrae in the lower back (L1-L5).
    Anterior Scalene Muscle
    The anterior scalene muscle is a deep neck muscle that elevates the first rib during inspiration and aids in neck flexion and stability, located between key neurovascular structures.
    Rotator Cuff Muscles
    Supraspinatus, Infraspinatus, Teres Minor, Subscapularis.
    Flexor Tendons
    Tendons that help flex the fingers and toes.
    Ligamentum Flavum
    Spinal ligament connecting the laminae of adjacent vertebrae.
    Anterior Longitudinal Ligament
    Spinal ligament running along the front of the vertebral column.
    Interspinous Ligament
    Spinal ligament between adjacent vertebral spinous processes.
    Quadriceps Tendon
    Tendon that connects the quadriceps to the patella.
    Acromioclavicular Joint
    The acromioclavicular joint connects the clavicle and scapula at the top of the shoulder, enabling smooth scapular motion and stability during arm movements.
    Rotator Cuff Tendons
    Tendons of the rotator cuff muscles.
    Femur
    Thigh bone, the longest and strongest bone in the body.
    Radius
    Forearm bone on the thumb side.
    Rectus Abdominis
    Abs muscle that flexes the trunk.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Sacrum
    Triangular bone at the base of the spine.
    Sacroiliac Ligaments
    Ligaments connecting the sacrum to the iliac bones.
    Syndesmoses
    Fibrous joints where bones are connected by ligaments.
    Adductors
    Muscles that bring the thighs toward the midline.
    Ilium
    Uppermost and largest part of the hip bone.
    Posterior Cruciate Ligament (PCL)
    Knee ligament that stabilizes the joint.
    Cervical Vertebrae (C1 - C7)
    Vertebrae in the neck region (C1-C7).
    Sphenoid Bone
    Bone forming part of the base of the skull and sides of the orbits.
    Temporalis
    Muscle involved in closing the jaw.
    Frontal Bone
    Bone forming the forehead and upper part of the orbits.
    Phalanges (14 bones)
    14 bones forming the toes.

    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 skull is made up of 22 bones.