A pectoral or pelvic appendage belonging to a paired vertebrate system. Comparative organization connects fin and limb histories while allowing extensive specialization.
An appendage with an inherited digit-bearing organization, which can be modified or lost in descendant lineages.
A hindlimb is the posterior paired limb of a tetrapod. Its segments and joints can be compared across walking, swimming, climbing and flying lineages. Similar topographic position does not require identical proportions or locomotor function.
A foot is the distal part of a hindlimb, including structures beyond the ankle in the familiar human arrangement. Its bones, joints and soft tissues distribute loads and provide leverage. The whole foot’s behavior cannot be reduced to the action of one joint.
The knee is the joint region linking thigh and leg, principally through femoral, tibial and patellar articulations. Its menisci, ligaments and muscles guide motion and distribute load. It permits substantial flexion and extension while requiring stability against translation and rotation.
The suprapatellar recess is an extension of the knee synovial cavity above the patella, deep to the quadriceps tendon. Its communication with the joint explains why joint fluid can accumulate superior to the patella. It differs from the superficial prepatellar bursa.
The infrapatellar fat pad is a fat-containing structure behind the patellar ligament and below the patella. It occupies changing space near the front of the knee and is closely related to the synovial lining. Intracapsular position does not make it part of the cartilage-bearing joint surface.
The posterior cruciate ligament links tibia and femur within the knee and restrains posterior translation of the tibia relative to the femur. Its effect depends on joint position and loading. It complements rather than duplicates the anterior cruciate ligament.
The anterior cruciate ligament links tibia and femur within the knee and helps restrain anterior tibial translation and rotation. Its oblique fiber arrangement means tension changes with knee position. It acts together with other ligaments, menisci and muscles.
The fibular collateral ligament runs on the lateral side of the knee from femur to fibula. It helps resist lateral opening of the joint under varus loading. Its fibular attachment distinguishes it from the medial tibial collateral ligament.
The tibial collateral ligament is the medial supporting ligament of the knee, connecting femur and tibia. It helps resist medial opening under valgus loading and has close relations to the medial meniscus. Those attachments differ from the more separate lateral collateral arrangement.
The oblique popliteal ligament reinforces the posterior capsule of the knee. It is associated with an expansion from the semimembranosus tendon. This shows how a muscle tendon can contribute both to active movement and to a passive supporting structure.
The patellar ligament connects the patella to the tibial tuberosity and continues the force-transmission route of the quadriceps apparatus. The quadriceps tendon is proximal to the patella. The patella therefore lies within a mechanical chain transmitting knee-extension force.
A fibrocartilaginous structure within the knee that helps distribute contact loads and contributes to stability. This anatomical meaning is distinct from a liquid surface.
The hip is the joint region connecting the femur to the pelvis. The femoral head articulates with the acetabulum, while capsule, ligaments and muscles stabilize movement. Its deeper socket favors a different mobility-stability balance from the shallower shoulder joint.
A distal finger or toe and its corresponding skeletal organization. Positional assignment, morphology and developmental identity must be distinguished when comparing reduced hands.
The thumb is the first digit of the human hand. Its basal joint and muscular control permit opposition toward other fingers, supporting precision grasp. Mobility, orientation and sensory control together explain its function more fully than digit length alone.
The morphological and developmental character identity assigned to a anatomical digit. It is not necessarily equivalent to its ordinal position among the surviving anatomical digits of a reduced limb.
Developmental assignment of position-associated anatomical and molecular character to a digit. A change in digit number or growth is not automatically a homeotic change of identity.
A condition with additional anatomical digits relative to the relevant standard pattern. In early digit-bearing vertebrates, counts above five show that the modern pentadactyl ground plan cannot simply be projected onto the earliest limbs.
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