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===Ungual (collateral) cartilages===

===Ungual (collateral) cartilages===

The ungual cartilages are extensions of the distal phalanx (Plll) that extend caudally and dorsally from the medial and lateral margins of Plll, curving inwards towards each other in the heel region.  The cartilages extend just beyond the confines of the hoof capsule making them palpable just above the coronary band at the lateral and medial edges of the foot.  The ungual cartilages can ossify resulting in ‘side bones’ which have the potential for fracturing.  The cartilages can also become infected resulting in the condition known as ‘quittor’.  

The ungual cartilages are extensions of the [[Phalanges_-_Horse_Anatomy#Distal_Phalanx|distal phalanx]] (Plll) that extend caudally and dorsally from the medial and lateral margins of the [[Phalanges_-_Horse_Anatomy#Distal_Phalanx|distal phalanx]], curving inwards towards each other in the heel region.  The cartilages extend just beyond the confines of the hoof capsule making them palpable just above the coronary band at the lateral and medial edges of the foot.  The ungual cartilages can ossify resulting in ‘side bones’ which have the potential for fracturing.  The cartilages can also become infected resulting in the condition known as ‘quittor’.  

The cartilages are securely attached to the other internal structures of the foot by a series of ligaments that extend from the medial and lateral cartilages to the distal and middle phalanx, the navicular bone, and the digital cushion.

The cartilages are securely attached to the other internal structures of the foot by a series of ligaments that extend from the medial and lateral cartilages to the distal and middle phalanx, the [[Phalanges_-_Horse_Anatomy#Distal_Sesamoid_.28Navicular.29_Bone|distal sesamoid bone (navicular)]], and the digital cushion.

===Collateral ligaments.===

===Collateral ligaments.===

The distal interphalangeal joint is enclosed within the hoof capsule.  It is stabilised by the medial and lateral collateral ligaments which form part of the joint capsule, connecting the distal end of Pll with the proximal edge of Plll.

The distal interphalangeal joint is enclosed within the hoof capsule.  It is stabilised by the medial and lateral collateral ligaments which form part of the joint capsule, connecting the distal end of Pll with the proximal edge of the [[Phalanges_-_Horse_Anatomy#Distal_Phalanx|distal phalanx]].

===Annular ligaments===

===Annular ligaments===

The annular ligament has its origins on the medial and lateral surfaces of distal Pl. It is the most superficial structure in the region, lying just beneath the skin and fusing with the DDFT where it enters the hoof capsule. Once inside the hoof the annular ligament merges with the fibrous attachments of the ungual cartilages and digital cushion, and continues with the DDFT down to its insertion onto Plll.

The annular ligament has its origins on the medial and lateral surfaces of distal Pl. It is the most superficial structure in the region, lying just beneath the skin and fusing with the [[Tendons_-_Horse_Anatomy#Flexorsdeep|digital flexor tendon]] where it enters the hoof capsule. Once inside the hoof the annular ligament merges with the fibrous attachments of the ungual cartilages and digital cushion, and continues with the [[Tendons_-_Horse_Anatomy#Flexorsdeep|digital flexor tendon]] down to its insertion onto the [[Phalanges_-_Horse_Anatomy#Distal_Phalanx|distal phalanx]].

===Sesamoidean ligaments===

===Sesamoidean ligaments===

The dorsal border of the navicular bone is held securely to the palmar/plantar surface of the distal phalanx by the distal sesamoidean ligament and to the proximal phalanx via the proximal interphalangeal collateral ligaments by means of a pair of medial and lateral collateral sesamoidean ligaments.  

The dorsal border of the [[Phalanges_-_Horse_Anatomy#Distal_Sesamoid_.28Navicular.29_Bone|distal sesamoid bone (navicular)]] is held securely to the palmar/plantar surface of the [[Phalanges_-_Horse_Anatomy#Distal_Phalanx|distal phalanx]] by the distal sesamoidean ligament and to the proximal phalanx via the proximal interphalangeal collateral ligaments by means of a pair of medial and lateral collateral sesamoidean ligaments.  

===Navicular bursa===

===Navicular bursa===

The navicular bone (distal sesamoid bone) lies between the second and third phalanges and the deep digital flexor tendon.  Associated with it is a fluid-filled sac that reduces friction between the bone and the DDFT that lies over the top of it— the navicular bursa.  Inflammation in the region is involved in navicular disease which is a common cause of lameness.  

The [[Phalanges_-_Horse_Anatomy#Distal_Sesamoid_.28Navicular.29_Bone|distal sesamoid bone (navicular)]] lies between the middle and distal phalanges and the deep digital flexor tendon.  Associated with it is a fluid-filled sac that reduces friction between the bone and the [[Tendons_-_Horse_Anatomy#Flexorsdeep|digital flexor tendon]] that lies over the top of it— the navicular bursa.  Inflammation in the region is involved in navicular disease which is a common cause of lameness.