Musculus quadriceps femoris -- vastus medialis
The vastus intermedius is the deepest quadriceps head, lying directly on the cranial femur. It originates from the cranial surface of the femoral shaft and inserts on the tibial tuberosity via the patellar ligaments. The vastus lateralis is the lateral component, originating from the lateral surface of the proximal femur and inserting on the lateral patellar ligament and tibial tuberosity. The vastus medialis is the medial component, originating from the medial surface of the proximal femur and inserting on the medial patellar ligament and tibial tuberosity. All extend the stifle. The vastus medialis is particularly important for medial stabilization of the patella. All are innervated by the femoral nerve (roughly L4-L5). Together with the rectus femoris they form the major anti-gravity muscle group of the hindlimb.
Origin: Medial surface of the proximal femur
Insertion: Medial patellar ligament and tibial tuberosity
Action: Extends the stifle; medially stabilizes the patella
Innervation: Femoral nerve (L4-L5)
Strain of the quadriceps can cause hindlimb lameness and reduced stifle extension. The vastus medialis is relevant in evaluations of patellar stability and upward fixation. Diagnosis is clinical and with ultrasound.
## Overview Medial patellar instability contributes to upward fixation of the patella, in which the hind limb intermittently locks in extension. Weakness of the vastus medialis and straight hind-limb
Sudden hindlimb lameness with swelling or pain over the front of the thigh after work should be evaluated. Rest and appropriate rehabilitation are important for recovery.
## Overview Medial patellar instability contributes to upward fixation of the patella, in which the hind limb intermittently locks in extension. Weakness of the vastus medialis and straight hind-limb conformation are predisposing factors. Catching or clicking at the stifle is common. Quadriceps-strengthening exercises often help. ## Causes Poor quadriceps tone, straight hind-limb conformation, or ligamentous laxity. ## Diagnosis Observation of intermittent locking or catching, and manipulation of the patella. ## Treatment Conditioning (hill work, backing), improved fitness, and in refractory cases medial patellar ligament desmotomy or splitting. ## Recovery and Prognosis Good with conditioning in mild cases. Surgical cases also do well. ## Prevention Maintain hindquarter fitness, especially in young or unfit horses. Signs include: intermittent locking of the hind limb in extension; catching or clicking at the stifle; improves with quadriceps strengthening
Strain of the quadriceps can cause hindlimb lameness and reduced stifle extension. The vastus medialis is relevant in evaluations of patellar stability and upward fixation. Diagnosis is clinical and with ultrasound.
Sudden hindlimb lameness with swelling or pain over the front of the thigh after work should be evaluated. Rest and appropriate rehabilitation are important for recovery.
See the Vastus Medialis on our interactive 3D horse model. Open 3D Model