Os femoris
The femur is the longest and heaviest bone in the horse. It extends from the hip joint to the stifle. The rounded femoral head articulates with the acetabulum of the pelvis to form the hip joint. The distal end has prominent trochlear ridges over which the patella glides, and the medial and lateral condyles form the femorotibial joints of the stifle. The entire bone is surrounded by the massive muscles of the thigh (quadriceps, biceps femoris, semitendinosus, etc.), which makes fractures difficult to image and stabilize. Its primary role is to transmit propulsive force from the hip to the stifle and lower limb while providing attachment for the largest muscles in the body. Because of its size and the surrounding musculature, adult femoral fractures generally carry a poor prognosis for return to athletic use.
Fractures in adult horses are difficult to repair and often have a guarded to poor prognosis due to the bone’s size, the forces involved, and the difficulty of external coaptation. Foals have a better outlook with internal fixation. Imaging usually requires radiography or advanced modalities; the heavy muscle cover limits ultrasound utility.
Damage to the femoral nerve (for example after general anesthesia or from iliopsoas muscle injury) paralyzes the quadriceps, so the horse cannot lock the stifle.
## Overview Fracture of the third trochanter of the femur is an uncommon injury, usually from direct trauma or avulsion. It causes hind-limb lameness and local swelling or pain on the lateral thigh.
## Overview Femoral fracture is a break of the thigh bone. In adult horses it usually results from severe trauma and carries a very poor prognosis. Most adult horses are euthanized. Foals have a some
## Overview Capital physeal fracture is a break through the growth plate of the femoral head in foals. It produces acute, severe hind-limb lameness. Because the physis is still open, the fracture occ
## Overview Coxofemoral luxation is dislocation of the femoral head from the acetabulum. It is uncommon in horses because of strong ligamentous support, but occurs more often in ponies and miniature
Sudden non-weight-bearing lameness in the hind limb after a fall, kick, or traumatic event should be evaluated immediately. Do not force the horse to move. Femoral fractures are surgical emergencies when repair is attempted.
Damage to the femoral nerve (for example after general anesthesia or from iliopsoas muscle injury) paralyzes the quadriceps, so the horse cannot lock the stifle. Signs include: Inability to fix the stifle in extension; the stifle and hock collapse when weight is placed on the limb; the horse cannot support weight on the affected hindlimb.
## Overview Fracture of the third trochanter of the femur is an uncommon injury, usually from direct trauma or avulsion. It causes hind-limb lameness and local swelling or pain on the lateral thigh. Diagnosis is by radiographs or ultrasound. Most are managed conservatively. ## Causes Trauma or muscle avulsion. ## Diagnosis Imaging of the proximal femur. ## Treatment Rest. Surgical removal of fragments is rarely needed. ## Recovery and Prognosis Good for most cases. ## Prevention Trauma avoidance. Signs include: hind-limb lameness; pain or swelling over the lateral proximal thigh; radiographic fracture of the third trochanter
## Overview Femoral fracture is a break of the thigh bone. In adult horses it usually results from severe trauma and carries a very poor prognosis. Most adult horses are euthanized. Foals have a somewhat better chance with internal fixation in selected cases. ## Causes High-energy trauma (falls, kicks, collisions). ## Diagnosis Acute non-weight-bearing lameness, swelling, crepitus, and radiographic confirmation. The limb may appear shortened or rotated. ## Treatment Surgical repair is rarely successful in adults due to implant and opposite-limb limitations. Foals may be candidates for internal fixation. Most adults are euthanized. ## Recovery and Prognosis Poor in adults. Guarded in foals even with surgery. ## Prevention Trauma avoidance. Signs include: acute non-weight-bearing lameness; severe swelling; crepitus; limb shortening or rotation; recumbency
## Overview Capital physeal fracture is a break through the growth plate of the femoral head in foals. It produces acute, severe hind-limb lameness. Because the physis is still open, the fracture occurs almost exclusively in horses under one year of age. Displacement of the femoral head compromises blood supply and joint congruity. ## Causes Trauma from falls, struggles, or kicks is the usual cause. The open physis is a weak point in the immature skeleton. ## Diagnosis Acute non-weight-bearing or severe lameness in a foal, pain on hip manipulation, and sometimes crepitus are suggestive. Radiographs confirm the physeal fracture and degree of displacement. ## Treatment Surgical reduction and internal fixation with pins or a screw-and-plate construct have been attempted. Success rates are low; many foals are euthanized because of poor prognosis, implant failure, or contralateral limb complications. Conservative management is rarely successful. ## Recovery and Prognosis Prognosis is poor. The majority of reported cases have been euthanized. Occasional foals have become pasture sound after successful fixation. ## Prevention Minimizing traumatic incidents in foals is the only practical measure. Signs include: acute severe hindlimb lameness in a foal; pain on hip manipulation; possible crepitus; non-weight-bearing stance
## Overview Coxofemoral luxation is dislocation of the femoral head from the acetabulum. It is uncommon in horses because of strong ligamentous support, but occurs more often in ponies and miniature horses, sometimes secondary to upward fixation of the patella. Trauma is the usual cause. The limb is typically non-weight-bearing with external rotation. ## Causes Severe trauma or, in small equids, violent contraction associated with locked patella. ## Diagnosis Characteristic stance (shortened limb, externally rotated, higher hock) plus radiographic confirmation. ## Treatment Closed reduction under general anesthesia is attempted early. Maintenance of reduction is difficult. Femoral head ostectomy is an option in small horses and ponies for chronic cases. Prognosis for athletic function is very guarded. ## Recovery and Prognosis Poor for return to work in large horses. Some ponies become pasture sound after reduction or ostectomy. ## Prevention Trauma avoidance; prompt treatment of upward patellar fixation in ponies. Signs include: non-weight-bearing hindlimb lameness; external rotation of the limb; asymmetrical pelvis; higher point of the hock
Fractures in adult horses are difficult to repair and often have a guarded to poor prognosis due to the bone’s size, the forces involved, and the difficulty of external coaptation. Foals have a better outlook with internal fixation. Imaging usually requires radiography or advanced modalities; the heavy muscle cover limits ultrasound utility.
Sudden non-weight-bearing lameness in the hind limb after a fall, kick, or traumatic event should be evaluated immediately. Do not force the horse to move. Femoral fractures are surgical emergencies when repair is attempted.
See the Femur (Left) on our interactive 3D horse model. Open 3D Model