Hamstring strains that involve the proximal free tendon and are more cranial to the ischial tuberosity have a longer recovery time to preinjury levels.
Carl M. Askling, P.T., of the Karolinska Institutet and Swedish School of Sport and Health Sciences, Stockholm, along with his colleagues evaluated acute first-time hamstring strains in 18 sprint runners.
The researchers measured the progression of clinical and MRI injury signs during the first 6 weeks after the injury. They then correlated those findings with the time it took the athletes to return to preinjury status (Am. J. Sports Med. 2007;35:197–206).
The sprinters, whose injuries occurred at maximal or close to maximal speed, stopped running immediately when the injury occurred, and 11 of the 18 (61%) fell. At the initial examination, 15 sprinters (83%) used crutches.
None of the sprinters reported any preinjury symptoms.
On palpation, all of the patients reported experiencing the most pain in the lateral rear thigh.
The mean distances from the point with the highest pain to the ischial tuberosity were measured at 2–4 days (12 cm), 10 days (11 cm), 21 days (12 cm), and 42 days (11 cm).
The corresponding mean lengths of the painful area were 11 cm, 7 cm, 6 cm, and 5 cm.
At the initial clinical examination, which occurred 2 days after injury, the sprinters estimated that they would return to preinjury levels after a median of 4 weeks.
The actual return was significantly longer: a median of 16 weeks (range, 6–50 weeks).
All of the sprinters could jog without pain at 6 weeks after injury, but only two (11%) could train or compete at their preinjury level.
During the 2-year follow-up period, three of the sprinters (17%) reinjured their hamstrings.
A significant correlation was seen between the location of highest pain during palpation at the first clinical examination and return to preinjury status, and there was a tendency toward a correlation at the second examination.
The more cranial the location, the longer was the return to preinjury level.
The investigators also discovered that free proximal tendon involvement was associated with longer recovery times.
There was no correlation between the palpated length of the painful area and the return to preinjury level.
Recovery prediction was equally as good when the point of highest pain on palpation—established within 3 weeks of injury—was used, as it was when the distance from the most cranial pole of the injury, as determined by MRI, was used.
“Repeated, carefully performed clinical examinations during the first 3 weeks after injury can give important information about the prognosis of a hamstring strain,” the authors wrote.
They added that MRIs are also useful for up to 6 weeks after injury in estimating recovery time.
Repeated, carefully performed examinations during the first 3 weeks after an injury will give key information about the prognosis of hamstring strain. ©Joshua Bickel/FOTOLIA