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    From Musculoskeletal System

    Zygomatic Bones
    Cheekbones that form part of the orbit.
    Acetabulum
    The acetabulum is the pelvic socket that connects with the femoral head to form the hip joint, vital for stability, movement, and weight-bearing.
    Temporal Bones
    Bones forming the lower sides of the skull and housing the ears.
    Annular Ligament
    The annular ligament is a strong fibrous band encircling the head of the radius, stabilizing the proximal radioulnar joint and allowing smooth rotation of the forearm.
    Lacrimal Bones
    Bones forming part of the eye socket and housing the tear ducts.
    Nasal Bones
    Bones forming the bridge of the nose.
    Patella
    Knee cap, protecting the knee joint.
    Maxillae
    Upper jaw bones that house the teeth and form part of the orbit.
    Thoracic Cage
    Ribs and sternum forming the protective cage for the heart and lungs.
    Hamstrings
    Biceps Femoris, Semitendinosus, Semimembranosus.
    Adductors
    Muscles that bring the thighs toward the midline.
    Sartorius
    Longest muscle in the body responsible for hip flexion.
    Hinge Joints
    e.g., elbow, knee
    Temporalis
    Muscle involved in closing the jaw.
    Gastrocnemius
    Calf muscle responsible for plantarflexion of the foot.
    Diaphragm
    Primary muscle for breathing.
    Palatine Bones
    Bones forming part of the hard palate and nasal cavity.
    Thoracic Vertebrae (T1 - T12)
    Vertebrae in the upper and mid-back (T1-T12).
    Latissimus Dorsi
    Back muscle responsible for arm adduction and extension.
    Biceps Tendon
    Tendon that attaches the biceps muscle to the bone.
    Gluteus Maximus
    Largest muscle in the buttocks responsible for hip extension.
    Sutures (in the skull)
    Fibrous joints between skull bones.
    Ethmoid Bone
    Bone forming part of the nasal cavity and the orbit.
    Flexor and Extensor Groups
    Muscles responsible for flexing and extending the hand and wrist.
    Anterior Cruciate Ligament (ACL)
    Knee ligament that stabilizes the joint.

    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? Your thumb has two phalanges, whereas other fingers have three.