Approach
Diagnosis of muscle sprains and strain relies on history of the mechanism of injury and clinical exam. Further diagnostic tests are required only if fracture or complete (grade 3) rupture is suspected.
History
In taking a history of the injury, the physician should ask about the following:
Time, circumstance, and type of trauma experienced, including its force and direction. Eccentric exercise is likely to cause injury at the musculotendinous junction. This type of exercise is associated with forcible lengthening of the contracting muscle (e.g., when lowering a weight or pitching a ball).
Onset and development of symptoms such as pain, swelling, bruising, loss of function, heat, and a sense of instability. Instability can indicate a significant sprain.
Experiencing a pop or snap at the time of the injury can signify a ruptured ligament or fractured bone.[23]
Any predisposing or aggravating conditions, such as epilepsy, anticoagulant treatment, or hemophilia.
Previous episodes, their management, and their outcomes.
Physical examination
General features on physical exam include:
Asymmetry, deformity, or wasting (the physician should compare the affected limb with the other):
A strain with complete rupture usually produces a sharp break in the normal outline of the muscle, with a dent under the skin where the ripped pieces of muscle have come apart.
Signs of heat over the site of the injury may be present, and, with time, may spread to adjoining areas.
Tenderness localized to the site of the damaged ligament or muscle.
Swelling and bruising:
The amount of swelling and bruising 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 bruising to become apparent.
Muscle strain often results in a large hematoma. In an intramuscular hematoma, bleeding is contained within the muscle sheath, resulting in pain and localized swelling. In an extramuscular hematoma, bleeding spreads through the intermuscular spaces; pain is less than that due to an intramuscular hematoma, and swelling is more diffuse.
Loss of function:
This initially worsens over the first few days as swelling increases.
Range of motion (ROM), both active and passive, may be affected.
Instability may be present in affected joints. All directions of movement should be checked for laxity.
Complete loss of muscle function suggests a severe strain with complete rupture.
To exclude other diagnoses, such as fracture or neoplasm, there should be absence of:
Bone tenderness.
Deformity, swelling, or asymmetry not due to the presenting sprain or strain.
Neurologic deficit, sensory or motor.
Lower limb injury
In ankle sprain, rupture of the lateral ligament complex should be considered if there is:
Pain during palpation of the anterior side of the lateral malleolus.
Visible bruising or laxity on pulling heel forward.
With regard to the commonly encountered Achilles tendon rupture, the following clinical maneuvers are imperative:[26]
Palpation for the presence of a gap.
The calf squeeze test (Thompson/Simmonds squeeze test): this is the clinical test with the highest sensitivity and specificity for Achilles tendon rupture. The test is 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 plantar flex a little (due to an intact plantaris) but should not plantar flex as much as the foot on the uninjured side.[26]
Matles test (increased passive ankle dorsiflexion). 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 uninjured side.[26]
Upper limb injury
In biceps tendon rupture (a frequently encountered presentation):[26]
Intactness is assessed by the biceps squeeze test, which is a similar maneuver to the Thompson test for Achilles tendon rupture.
The Hook test for complete biceps tendon avulsions is also strongly suggestive. This test 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.[27]
X-rays
Radiography should be arranged only if a fracture requiring specific treatment is suspected or needs to be excluded.
Ottawa ankle rules[28]
An ankle x-ray series is indicated for someone with an ankle injury and either:
Bone tenderness at the posterior edge or tip of either the lateral or medial malleolus, or
Inability to bear weight both immediately after the injury and for 4 steps when examined.
Ottawa knee rules[29]
A knee x-ray series is indicated for people with a substantial knee injury and any of the following:
Age ≥55 years
Isolated tenderness of patella (no bone tenderness of knee other than patella)
Tenderness of head of fibula
Inability to flex to 90°
Inability to bear weight, both immediately and in the emergency department, for 4 steps.
MRI
MRI can be helpful to confirm diagnosis; to determine the extent of injury, especially to differentiate between partial tear and complete tear; and to look at other associated injuries.[30] It is not routinely used as an initial imaging study for acute trauma to the ankle.[31]
MRI should be ordered if:
Pain is ongoing
Pain is out of proportion despite treatment
Symptoms do not improve in reasonable time
Function worsens despite treatment
Any other associated structure involvement is suspected.
Ultrasound or MRI is often necessary to confirm the diagnosis of tendon rupture. If imaging is indicated, MRI is preferred and will show intact muscle with retraction of the tendon. However, MRI may not be appropriate for all tendon injuries. For example, avoid routinely ordering MRI in patients with suspected acute Achilles tendon rupture, which is a clinical diagnosis.[32] MRI is considered gold standard in identifying acute ligamentous injuries of the ankle.[33]
For most musculoskeletal injuries in children, do not order MRI scans (or other advanced imaging studies, e.g., CT) until all appropriate clinical and plain radiographic exams have been completed.[34]
Ultrasound
Ultrasound can be used to define the nature of muscle strain. It is not useful for ligament sprains.
Ultrasound or MRI may be necessary to confirm the diagnosis of tendon rupture. The diagnostic reliability of ultrasound is observer-dependent and requires a skilled practitioner.[35]
Diagnostic arthroscopy
Arthroscopy is useful in evaluation when there is some associated injury that needs to be addressed at the same time: for example, to rule out osteochondral injury in ankle sprain.
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