Key diagnostic factors

acute onset of symptoms (common)

• Can suggest sprain or strain.

mechanism of injury (common)

• The time, circumstances, and kind of trauma experienced, including its force and direction.
• Eccentric exercise is likely to cause injury at musculotendinous junction. This type of exercise is associated with forcible lengthening of the contracting muscle (e.g., when lowering a weight).

severe pain (common)

• Pain that seems out of proportion to the injury and its mechanism can indicate grade 3 injury or complete rupture.

swelling (common)

• The amount depends partly on severity and partly on the time since the injury, as it can take up to 24 hours for the full extent of swelling to become apparent.

bruising (common)

• Muscle strain often results in a large haematoma. In an intramuscular haematoma, bleeding is contained within the muscle sheath, resulting in pain and localised swelling. In an extramuscular haematoma, bleeding spreads through the intermuscular spaces; pain is less than that due to an intramuscular haematoma, and swelling is more diffuse.

palpable gap in normal position for Achilles tendon (Achilles tendon rupture) (common)

• May be detected in patients with Achilles tendon rupture. [24]

positive calf squeeze test (Achilles tendon rupture) (common)

• Also called Thompson/Simmonds test.
• Clinical test with the highest sensitivity and specificity for Achilles tendon rupture. Performed by asking the patient to lie prone with his/her feet over the end of the examination couch. The examiner squeezes the patient’s calf, just distal to the thickest point. With an intact Achilles tendon, the foot should plantar flex. With a ruptured Achilles tendon, the foot may still plantar flex a little (due to an intact plantaris) but should not plantar flex as much as the foot on the uninjured side. [24]

positive Matles test (Achilles tendon rupture) (common)

• To perform this test, the patient is asked to lie prone with his/her knees flexed to 90 degrees. In the presence of an Achilles tendon rupture, the foot on the injured side should assume a position that is more dorsiflexed than that of the other side. [24]

positive biceps squeeze test (biceps tendon rupture) (common)

• Assesses intactness of the biceps tendon. [25]

positive Hook test (biceps tendon rupture) (common)

• A positive test is strongly suggestive for the complete biceps tendon avulsion.
• Involves the patient actively supinating the arm with the elbow flexed to 90 degrees. The examiner then attempts to hook his/her index finger under the biceps tendon from the lateral side. This should be possible with an intact biceps tendon. However, with a distal avulsion of the biceps tendon, the examiner should not be able to feel a cord-like structure and therefore is unable to hook a finger under it. [26]

pop sound (uncommon)

• History of pop sound can suggest grade 3 strain

deformity (uncommon)

• More common with fractures than with sprain or strain.

Other diagnostic factors

previous injury (common)

• History of multiple minor injuries can point towards severe muscle sprain as opposed to fracture.

symptom duration more than a few days (common)

• Can suggest more severe grades of injury.

limited ROM (common)

• Limitation of ROM is more common in the acute phase. Failure to gain motion despite improvement in pain and swelling can suggest grade 3 strain.

weakness (common)

• More common in acute phase due to painful inhibition of contraction.