The semitendinosus and gracilis muscles are found on the back and inner aspects of the thigh, and
are responsible for flexing the stifle, or knee joint. The tendons of these muscles also form part of
the Achilles tendon. Semitendinosus and gracilis myopathy, also known as fibrotic myopathy, occurs
when the normally elastic muscle tissue is replaced with dense connective tissue, similar to scar tissue.
Because the connective tissue is not able to stretch like muscle does, the affected muscle become
shortened, or contracted. It can occur in other muscles as well, such as the quadriceps, infraspinatus,
and supraspinatus muscles. (diagram of muscle anatomy)
Who gets Semitendinosus and Gracilis Myopathy?
Semitendinosus and gracilis myopathy is a relatively uncommon condition, but occurs most frequently
in German Shepherds. Belgian Shepherds, Greyhounds, Doberman Pinschers, Rottweilers, St. Bernards,
Boxers, and Old English sheepdogs may also be affected. Dogs with fibrotic myopathy tend to be young
adult dogs, and may develop the condition as early as 8 to 9 months of age.
What are the Signs of Semitendinosus and Gracilis Myopathy?
Dogs with semitendinosus and gracilis myopathy usually have a history of gradual onset of hind limb
lameness, weakness, and pain. The formation of scar tissue in replace of muscle leads to decreased
range of motion. It also produces a very characteristic gait, in which the dog’s stride is shorter with
a rapid elastic inward rotation of the paw, and an internal rotation of the stifle (knee). At first, the
lameness gets progressively worse, but signs plateau weeks to months after onset. (video of altered
How is Semitendinosus and Gracilis Myopathy Diagnosed?
Your veterinarian can diagnose this condition based on a history of lameness, and the altered gait
described above. Upon physical exam, the affected muscles will feel firmer than normal due to the
formation of the connective tissue. Diagnosis can be confirmed usually ultrasound of the muscle, and
can help assess the extent and severity of the condition.
Why did my Dog get Semitendinosus and Gracilis Myopathy?
The definitive cause of semitendinosus and gracilis myopathy is unknown, but is hypothesized to be
caused by trauma, immune-mediated disease, or may be secondary to a disease process involving the
How is Semitendinosus and Gracilis Myopathy Treated?
Unfortunately, there is no known treatment that is entirely effective in correcting this condition. Surgery
can be performed to remove the affected muscle, but recurrences of clinical signs are usually seen
anywhere from 6 weeks to 5 months post-op, due to the formation of new scar tissue. In some cases,
aggressive physical therapy may be beneficial, but usually is most effective in combination with surgery.
Can Semitendinosus and Gracilis Myopathy be Prevented?
Because so little is known about the cause of fibrotic myopathy, it cannot be said whether or not the
condition is preventable. However, if muscle injury occurs and is identified early, intermittent rest and
ice may minimize permanent muscle damage. Following acute injury, strengthening and range of motion
exercises should be performed, taking precautions to minimize additional muscle trauma.
What is the Prognosis for my Dog with Semitendinosus and Gracilis Myopathy?
Prognosis for semitendinosus and gracilis myopathy is generally poor or guarded, because even with
surgery, clinical signs will return. Long-term physical rehabilitation following surgery may improve the