Anatomy of the Distal Lower Limb

Distal Lower Limb

• The distal lower limb is divided into the foot, lower leg, and distal femur
• The ankle and knee joints are also discussed
• The bones of the foot are similar to the bones of the hand and wrist
• The foot contains 26 bones divided into three groups: phalanges, metatarsals, and tarsals

Foot Bones

• Phalanges (Toes): The most distal bones, numbered 1 to 5, starting with the big toe. The first toe only has proximal and distal phalanges. Second to fifth toes each have a middle phalanx in addition to the proximal and distal phalanges. There are 14 phalanges in total in one foot. They are similar to the hand phalanges, but smaller and less flexible.
• Metatarsals (Instep): Five bones numbered 1 to 5, with 1 on the medial side and 5 on the lateral side. Each has a head, body (shaft), and base. The base of the fifth metatarsal is enlarged with a tuberosity for tendon attachment and often a trauma site.
• Tarsals: The remaining bones in the foot.

Joints of Phalanges (Digits) and Metatarsals

• Phalangeal Joints: Important for fracture identification. Each joint's name is derived from the two bones on either side.
  • Interphalangeal (IP) joint: Between the proximal and distal phalanges of the first toe and between the middle and distal phalanges for digits 2-5.
  • Proximal interphalangeal (PIP) joint: Between the proximal and middle phalanges for digits 2-5
• Metatarsal Joints:
  • Metatarsophalangeal (MTP) joint: At the head of each metatarsal
  • Tarsometatarsal (TMT) joint: At the base of each metatarsal

Sesamoid Bones

• Small, detached bones often found near various joints in the feet and hands, embedded in tendons.
• Can be present near metacarpophalangeal joints or interphalangeal joints in the upper limbs.
• In the lower limbs, they tend to be larger and significant radiographically.
• The largest sesamoid is the patella.
• Ones near the first metatarsal and first MTP joint are frequently found
• Tibial and fibular sesamoid bones are on the medial and lateral sides, respectively.
• Fractures can be a possible cause of pain and discomfort when weight is placed on the foot.