An amateur soccer player experienced a painful crack along the posteromedial aspect of the right knee during sprinting. The semitendinosus tendon was neither visible nor palpable on physical examination. Knee movements were preserved; no instability was clinically appreciable.
A MRI of the knee, performed a week after the event, showed distal detachment and retraction of the semitendinosus tendon, which was irregularly thickened and inhomogeneous (Fig. 1-4); a small fluid collection circumscribed the tendon; oedema of the surroundings was also evident (Fig. 2, 4).
On T2w-MRI strain of the semimembranosus muscle was appreciable (Fig.3e, f); MRI ruled out other injuries of the knee.
Injuries to the hamstring tendons and muscles are common in sprinting sports. In high level athletes with a hamstring strain MRI evaluation is positive in 68-81% of cases. The biceps femoris long head is more commonly involved (66-87% of cases), whereas semimembranosus and semitendinosus injuries are both found in 32-37% of cases; the biceps femoris short head is less frequently involved and only in distal injuries [1, 2]. In approximately one third of patients MRI reveals lesions of more than one tendon or muscle; hamstring strain is proximally located in half of cases, distally in 40% of cases, whereas midhamstring strain, involving muscle only, occurs in approximately 10% of cases [2].
Rupture of the distal semitendinosus tendon is rare, but probably underestimated, likely because of inadequate MRI examinations; history reveals pain or minor injury predating the rupture in 15% of patients only [1]. Tendonitis or intrasubstance tear are likely predisposing factors to complete tendon rupture [3].
Semitendinosus tendon retraction, degenerative changes of the tendon, decrease muscle volume and oedema are appreciable on MRI in acute/subacute phase; atrophy of the muscle belly and some degree of fibrosis, arranged in a concentric onion-like fashion circumscribing the tendon on axial imaging, can be observed in chronic rupture [1, 4, 5].
Hamstring injury diagnosis can be clinically easy to achieve; the role of imaging is essential to establish severity and extension of the lesion [2]. Ultrasound is very competitive with MRI in diagnosing hamstring injury. Advantages of ultrasound are low cost, rapid investigation time, possibility of dynamic examination, comparison with contralateral thigh and knee, spatial resolution, and diagnostic accuracy despite retained metallic objects.
Nevertheless, beyond inherent diagnostic sensitivity, MRI of the thigh and knee plays a pivotal role in grading hamstring injury, the prognosis relying on the following findings [2]:
- number of muscles or tendons involved;
- injury location for each muscle or tendon (origin avulsion, proximal myotendinous junction, muscle belly, distal myotendinous junction, insertion avulsion);
- cross-sectional percentage of each lesion on axial MRI;
- tendon or muscle retraction;
- associated signs of chronic tendinopathy;
- craniocaudal sagittal extent of the lesion.
MRI investigation is also mandatory when associated traumatic lesions of the knee should be ruled out and for therapeutic management, especially in preoperative planning, when the orthopaedist dictates indications for surgery.
Distal semitendinosus tendon rupture
The patient is a 44-year-old female amateur soccer player who suddenly felt a “painful tearing sensation” in the posteromedial aspect of her right knee during a sprint. Based on the provided axial and sagittal MRI images of the knee, the following observations are noted:
Considering the clinical presentation and MRI findings, the following possibilities are proposed:
Considering the patient’s athletic background, the onset during sprinting with a sudden “tearing sensation,” the absence of palpation of the tendon in the posteromedial knee, and MRI findings indicating tendon discontinuity and edema, the most likely diagnosis is:
Rupture of the Distal Semitendinosus Tendon in the Right Knee
If clinical or imaging questions remain, further high-resolution ultrasound examinations may clarify the residual tendon fibers and the extent of the tear. Arthroscopy or surgical exploration can be considered if necessary for definitive confirmation.
For distal semitendinosus tendon rupture, treatment should be tailored to the extent of the tear, functional requirements, and the patient’s athletic goals:
Rehabilitation exercises should follow the FITT-VP principle progressively:
If the patient has other underlying conditions (e.g., osteoporosis, compromised cardiopulmonary function, etc.), training intensity and duration should be adjusted accordingly. Knee pain, swelling, and overall function should be closely monitored throughout rehabilitation.
This report provides a reference-based analysis using imaging and clinical information. It does not replace face-to-face consultation or the opinions of medical professionals. Patients should develop and carry out individualized treatment plans under the guidance of specialists and rehabilitation therapists. Please seek medical attention promptly if there are any questions or changes in condition.
Distal semitendinosus tendon rupture
