Figure 1. Sagittal view of the injured knee on MRI.
Figure 2. Posterior view of the knee on MRI.
A 33-year-old man presents to the office with left knee pain that started 3 weeks earlier. The patient notes that he was sprinting when he experienced a noncontact twisting injury to the knee. At the time of the injury, he felt a pop at the medial aspect of the knee and the area began to swell over the next few days. He has had ongoing medial-side knee pain that worsens with twisting, squatting, and kneeling. Magnetic resonance imaging (MRI) of the left knee (Figures 1 and 2) demonstrates a distal semitendinosus tendon avulsion with proximal retraction.
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Hamstring injuries are common and generally involve proximal muscle tears or tendon avulsions off the ischial tuberosity. Distal hamstring tears and tendon avulsions are far less common.1,2 The hamstring muscles include the semitendinosus, semimembranosus, and biceps femoris, which has a long and short head. The distal biceps femoris tendon attaches to the lateral aspect of the knee and is the most common distal hamstring injury, typically associated with a varus hyperextension injury. Semitendinosus injuries occur from the attachment side over the medial knee (at the pes anserine).1-3
The most common findings on physical examination of a semitendinosus injury include pain with knee extension, swelling on the medial knee, and tenderness over the pes anserine. The best imaging test to identify these injuries is MRI. Treatment of these injuries is controversial, as they are rarely seen.1-3
Because the semitendinosus is harvested for anterior cruciate ligament (ACL) autografts with little to no clinically significant loss in hamstring strength postoperatively, nonoperative treatment for avulsion injuries is a reasonable option. Sekhon et al treated 2 professional athletes successfully with nonoperative treatment and a rapid return to sports (within 1-4 weeks).1 Adejuwon et al found that full recovery from a semitendinosus avulsion injury was achieved in 2 elite adult sprinters with nonoperative treatment. Full recovery with return to preinjury level of play occurred at 12 months.2 Conversely, Cooper et al found that elite athletes returned to sport sooner when undergoing surgical repair within 4 weeks of injury compared to nonoperative treatment.3 The authors’ criteria for acute surgical repair include elite athletes who desire an earlier return to play, patients who fail to progress with a nonoperative rehabilitation program, and continued knee extension pain.3 Surgical excision of the semitendinosus tendon is also a reasonable option if patients have continued medial-sided knee pain.3
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopaedics for Physician Assistants.
1. Sekhon JS, Anderson K. Rupture of the distal semitendinosus tendon: a report of two cases in professional athletes. J Knee Surg. 2007;20(2):147-150. doi:10.1055/s-0030-1248034
2. Adejuwon A, McCourt P, Hamilton B, Haddad F. Distal semitendinosus tendon rupture: is there any benefit of surgical intervention. Clin J Sport Med. 2009;19(6):502-504. doi:10.1097/JSM.0b013e3181bd09c7
3. Cooper DE, Conway JE. Distal semitendinosus ruptures in elite-level athletes: low success rates of nonoperative treatment. Am J Sports Med. 2010;38(6):1174-1178. doi:10.1177/0363546509361016