Musculus semitendinosus
The semitendinosus has two heads. The vertebral head originates from the last sacral and first two caudal vertebrae, tail fascia, and sacrosciatic ligament. The pelvic head originates from the ventral aspect of the ischial tuberosity. It inserts on the cranial border of the tibia, crural fascia, and via a tarsal tendon on the calcaneus (as part of the common calcanean tendon). Its actions depend on limb position: in the weight-bearing limb it extends the hip, stifle, and hock joints; in the non-weight-bearing limb it flexes the stifle and retracts and adducts the limb. A bursa lies between the ischial tuberosity and the vertebral head. It is innervated by the caudal gluteal and sciatic nerves (tibial branch, roughly L6-S2).
Origin: Ischial tuberosity, sacrotuberous ligament, and first caudal vertebrae
Insertion: Tibial crest and calcaneal tuber (via the common calcanean tendon)
Action: Extends the hip and hock; flexes the stifle
Innervation: Sciatic nerve — tibial branch (L6-S2)
Strain can cause hindlimb lameness and reduced propulsion. Relevant in evaluations of caudal thigh trauma or after overexertion. Diagnosis is clinical and with ultrasound.
## Overview Semitendinosus strain occurs from explosive hip extension during racing or jumping. It produces acute hind-limb lameness, swelling and heat over the caudal thigh, a shortened stride, and
## Overview Fibrotic myopathy is scarring and contracture within a muscle, most often the hamstring group (semitendinosus). It produces a characteristic mechanical gait in which the foot slaps down a
Sudden hindlimb lameness with swelling or pain in the caudal thigh after work should be evaluated. Rest and controlled rehabilitation are important.
## Overview Semitendinosus strain occurs from explosive hip extension during racing or jumping. It produces acute hind-limb lameness, swelling and heat over the caudal thigh, a shortened stride, and reluctance to fully extend the hip. Palpation of the hamstring region is painful. ## Causes Sudden maximal contraction during acceleration or takeoff. ## Diagnosis Clinical examination and ultrasound. ## Treatment Rest, anti-inflammatories, and gradual return to work. ## Recovery and Prognosis Good for most strains. Fibrotic myopathy can be a sequela. ## Prevention Adequate conditioning for the level of work. Signs include: acute hind-limb lameness; swelling and heat over the caudal thigh; shortened stride; pain on hamstring palpation; reluctance to extend the hip
## Overview Fibrotic myopathy is scarring and contracture within a muscle, most often the hamstring group (semitendinosus). It produces a characteristic mechanical gait in which the foot slaps down abruptly before completing the forward swing. The condition is usually non-painful and often follows trauma or an intramuscular injection. ## Causes Trauma, tearing, or injection-site fibrosis leading to muscle contracture. ## Diagnosis Classic gait at the walk plus palpation of a firm fibrous band. Ultrasound confirms the scar. ## Treatment Many horses need no treatment. Severe cases may undergo surgical transection of the fibrotic band. Conservative therapy (stretching, controlled exercise) helps some. ## Recovery and Prognosis The gait abnormality is often permanent but non-progressive. Surgery improves some horses. ## Prevention Careful injection technique in the hamstring region. Signs include: foot slaps down early in the swing phase; mechanical non-painful gait; shortened forward stride; firm band in the muscle; usually unilateral
Strain can cause hindlimb lameness and reduced propulsion. Relevant in evaluations of caudal thigh trauma or after overexertion. Diagnosis is clinical and with ultrasound.
Sudden hindlimb lameness with swelling or pain in the caudal thigh after work should be evaluated. Rest and controlled rehabilitation are important.
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