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.
- The hip/femoroacetabular joint, like the shoulder/glenohumeral joint is a ball and socket triaxial joint.
- The knee joint is actually composed of two articulations: medial and lateral tibiofemoral joints.
- The fibula is not functionally a part of the knee joint; it is functionally important to movement at the ankle joint.
- The patella articulates only with the femur, not with the tibia.
- There are three tibiofibular joints: proximal, middle, and distal.
- The ankle joint is a hinge joint that allows only dorsiflexion and plantarflexion of the foot.
- 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.
- Pronation and supination also occur at the transverse tarsal joints.
- The metacarpophalangeal joint of the big toe is functionally extremely important during the gait cycle (walking).
- There is one interphalangeal joint in the big toe.
- Toes 2-5 have two interphalangeal joints each: proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints.