Lower Extremity Joints

The joints of the lower extremity are:

• Sacroiliac joints (SIJs) between the sacrum and iliac portion of the pelvic bones.
• Pubis symphysis joint between the two pubic symphyses of the pelvic bones.
• Hip (femoroacetabular) joints between the head of the femur and the acetabulum of the pelvic bone.
• Knee joints between the distal end of the femur and the proximal end of the tibia.
• Patellofemoral joints between the patella and femur.
• Ankle joints between the distal ends of the tibia and fibula and the talus of the tarsal bones.
• Intertarsal joints between individual tarsal bones.
• Subtalar joints between the talus and calcaneus.
• Transverse tarsal joints between talus and calcaneus proximally and the navicular and cuboid distally.
• Tarsometarsal joints between the distal row of tarsals and the metatarsals.
• Intermetatarsal joints located between the metatarsals.
• Metatarsophalangeal joints between the metatarsals and proximal phalanges.
• Interphalangeal (IP) joints between the phalanges.

NOTES:

1. The hip/femoroacetabular joint, like the shoulder/glenohumeral joint is a ball and socket triaxial joint.
2. The knee joint is actually composed of two articulations: medial and lateral tibiofemoral joints.
3. The fibula is not functionally a part of the knee joint; it is functionally important to movement at the ankle joint.
4. The patella articulates only with the femur, not with the tibia.
5. There are three tibiofibular joints: proximal, middle, and distal.
6. The ankle joint is a hinge joint that allows only dorsiflexion and plantarflexion of the foot.
7. Inversion and eversion of the foot are cardinal-plane components of larger oblique-plane motions patterns known as pronation and supination, which occur primarily at the subtalar joints.
8. Pronation and supination also occur at the transverse tarsal joints.
9. The metacarpophalangeal joint of the big toe is functionally extremely important during the gait cycle (walking).
10. There is one interphalangeal joint in the big toe.
11. Toes 2-5 have two interphalangeal joints each: proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints.

Anterior view of the joints of the lower extremity on the right side of the body.

Posterior view of the joints of the lower extremity on the right side of the body.