Considerations in the Diagnosis of Injury
When making a diagnosis, the first step is to differentiate between different categories of injury—particularly between indirect and direct muscle injuries, and between functional (nonstructural) and structural muscle injuries. This is important because these injury types have a different prognosis, causing different absences.
Indirect muscle injuries
Direct muscle injuries
Functional muscle injury
Structural muscle injury
Painful muscle injury/disorder without macroscopic evidence (visible in MRI/ultrasonography) of a muscle fiber tear
Any acute distraction injury to a muscle with macroscopic evidence (visible in MRI/ultrasonography) of a muscle fiber tear
Direct muscle trauma caused by blunt external force (leading to diffuse or circumscribed hematoma)
Direct muscle trauma/wound (including the skin and subcutaneous tissue) caused by sharp external force
Abbreviation: MRI, magnetic resonance imaging.
Note: Imaging is usually precise enough to determine if there is a relevant tear or not. However, imaging alone is not appropriate for determining a diagnosis and the extent of a muscle injury.
4.2.1 Indirect Injuries
Indirect injuries are usually caused by internal forces. They are broken down into functional (nonstructural) and structural types. 5
Functional (Nonstructural) Injuries
Functional injuries/disorders are minor injuries causing swelling, edema, and painful firmness of the muscle. Players are unable to compete because of functional limitations such as painful increases in muscle tone. These injuries are multifactorial and can occur for various reasons. They can represent a risk factor for structural injuries (partial tears).
Structural injuries (tears) are induced by stretching and are caused by a sudden forced lengthening, in excess of the muscle’s viscoelastic limits, during a powerful contraction (i.e., an internal force).
There are different types and grades of each category, as described in ▶ Table 3.2.
Fig. 4.1 Information sources used for diagnosis of injury.
4.2.2 Direct Injuries
Direct injuries (i.e., contusions and- less frequently – lacerations) are caused by external forces, such as a direct blow from an opponent’s knee. The most frequently contused muscles are the exposed rectus femoris, the vastus lateralis, and the vastus intermedius, which lies next to the bone. Contusion injuries can lead to bleeding, causing pain and a loss of motion, but muscle fibers are not typically torn by longitudinal distraction. For this reason, players with contusions can often continue playing for some time, whereas even a small indirect structural injury often forces the player to stop at once.
It has been shown that the incidence of indirect injuries is eight times higher (1.48/1,000 hours) compared to direct muscle injuries (0.19/1,000 hours; p < 0.01), indirect muscle injuries cause 19% of total absence, and direct injuries 1%, and that the mean layoff time for indirect injuries is 18.5 days, which differs significantly from direct injuries with 7.0 days (p < 0.001). 6 Foul play is involved in 7% of all thigh muscle injuries, in 2% of indirect injuries, and 42% of direct injuries. 7
4.3 Examination of Muscle Injuries
External trauma suggests contusion.
Mechanism (sprinting, shooting, landing, overstretch, etc.)?
Sprinting is more likely to affect the hamstrings. 8
Shooting is more likely to affect the rectus femoris muscle. 8
Slow movements such as stretching can cause injuries involving longer absences. 9
Fall after injury?
A fall points to a more severe injury with functional loss.
Type of pain (pain at rest, cramp-like, sharp, etc.)?
Cramp-like pain indicates a more functional injury;
“Snap” or “tearing”?
This suggests a structural injury/tear.
Onset of pain (slow or sudden)
Slow onset of pain indicates a functional injury;
4.3.1 Medical History/Symptoms
The examiner should start with a precise history of the circumstances surrounding the injury, before reviewing the player’s symptoms and identifying any previous related injury problems. 9, 10 Where the player reports a sharp and sudden onset of pain (e.g., the player experiences a “snap” and well-defined, localized pain), a tear must be assumed ( ▶ Table 4.4).
This can influence the current injury.
Previous scarring can influence the current injury.
Muscle firmness/tightness or fatigue?
This can predispose the athlete to structural injuries.
Dysfunction of the lower back can cause peripheral muscle complaints, such as muscle tightness.
4.3.2 Inspection, Clinical Examination, Functional Testing, and Location of Injury
The next step in diagnosis is a careful clinical examination of the injured area ( ▶ Table 4.5). This should include an inspection, palpation, a comparison with the contralateral side, and functional testing of the muscles.
This usually determines the severity of the injury.
This suggests a structural injury/tear.
Retraction of muscles?
This suggests a severe injury/tear.
Changes to contours of muscle?
This suggests a severe injury/tear.
Always start with an inspection of the injured leg. Is there any swelling or a visible hematoma (see ▶ Fig. 4.2a)? Inspect the contours of the muscle and ask the athlete to tense the muscles, and to pull the legs up. Assess how the muscle looks and whether there is any muscle retraction (see ▶ Fig. 4.2b).
Fig. 4.2 (a) Hematoma visible on the surface (+) is not always located directly at the site of the injury. In this case, the hematoma (+) is located distally. The tear (which was revealed and marked using a clinical examination and ultrasonography) is in the biceps femoris muscle the center of the lines (–), at the point marked by the asterisk (*).(b) A proximally retracted muscle belly (+) surrounded by (dashed line) after a subtotal muscle tear (blue arrows) of the long head of the biceps femoris muscle in an elite football player.
Note: Hematomas, muscle retraction, and changes to the contours of a muscle are only seen in structural injuries.
Strength assessment of the muscles is recommended, which should be done via manual resistance. A functional examination of the adjacent joints should be performed next, as well as dynamic testing of the tensed muscles. In the case of a hamstring injury, the range of motion of the hip and the knee in the injured leg can decrease relative to the healthy leg. 3 Passive straight leg raise (hip) and active knee extension test (knee) can be used to assess hamstring flexibility and maximum length. However, in the acute phase, these tests are usually limited by pain and thus are not very objective. 11
Careful passive prestretching of the affected muscles can help to differentiate between a tear (which is usually painful on stretching) and a functional injury (which can be relieved with stretching in certain cases).
Palpation gives the examining physician an impression of the affected muscles in comparison with the muscles of the uninjured, contralateral side. 12 Palpating a muscle indicates its tone, the condition of the musculature, and possible adhesions, scarring, etc., which is essential for evaluating the player’s readiness to play again. While imaging such as ultrasonography and MRIs can supplement these impressions, they cannot replace them 5 ( ▶ Table 4.6).
Localized or larger area?
This helps to identify injury location.
This helps to determine injury type.
This also helps to identify injury location and injury type.
Pain/relief on careful stretching?
Pain on stretching suggests a tear.
A defect is most likely to indicate a structural injury.
Palpation is performed with moderate pressure and movement. The fingers should repeatedly slide along the muscle from distal to proximal, back, and across the fibers, but should not only press down on the muscle. When conducting palpation, ask the athlete to demonstrate where the center of pain is located. Palpation reveals if there is any pressure pain, and whether the pain is localized or covers a larger area. It also helps to detect if the muscle is edematous, whether there is pain or relief on careful stretching, and if there is a palpable defect. 13
Note: Muscle tension/tightness etc. can be assessed only by means of clinical examination, not with imaging.
Palpation of the hamstrings, for example, is performed first with the knees fully extended. In this position, the muscles are slightly stretched (see ▶ Fig. 4.3a), whereas with flexed knees, the hamstrings are more relaxed (see ▶ Fig. 4.3b). The hand and finger(s) should slide over the muscles several times, getting an impression of the muscle tone and searching for an area with an increase in tone relative to the adjacent muscle.
Fig. 4.3 (a) The examination is first performed with fully extended knees (i.e., passively slightly tensed hamstrings). (b) The second part of the examination. Here, the more relaxed muscles are palpated, the lower leg is supported underneath by the examiner’s knee.
At the same time, the athlete should be observed to note if there is any reaction to pressure on account of pain. 13
Note: A structural injury (i.e., a tear) is usually located within a firm muscle band.
Note: A precise clinical examination of muscles takes time.
4.3.4 Location of Injury
Typically, structural injuries are located in the distal part of the biceps femoris, along the semitendinosus or semimembranosus muscle, or along the intramuscular tendon of the rectus femoris muscle (see ▶ Fig. 4.4a, b). It is usually the weakest point that tears. In most athletes, this is the musculotendinous junction; in adolescents, it is the apophysis; 14 and in older patients, it is the tendon.
Fig. 4.4 (a) Posterior thigh; typical locations of structural injuries. Hamstrings: Tears occur most frequently in the muscle-tendon junction of the distal biceps femoris, caput longum (1). Structural injuries can also occur along the musculotendinous junction of the semimembranosus and semitendinosus muscles (2). (b) Anterior thigh. Rectus femoris and adductors: Structural injuries are frequently observed in the proximal rectus femoris (1), along its intramuscular tendon (2), and along the intramuscular tendon of the adductor longus muscle (3).
The location of the injury should be identified through clinical examination ( ▶ Table 4.7). The examination should determine whether the muscle problem is within the muscle belly, in the muscle–tendon junction, in the tendon–bone junction, or along the intramuscular tendon.
This is typical of some functional injuries.
This is typical for structural injuries/tears.
This is typical for tendinous avulsions.
Intramuscular tendon involved?
This is typical for structural injuries in certain muscles (e.g., Rectus femoris).
Note: Mark the location of the injury after the clinical examination (see ▶ Fig. 4.5).
Fig. 4.5 After clinical examination (and/or an ultrasonography), the location of the injury (where the lines meet) can easily be marked on the skin to limit the field of view in a possible subsequent MRI and/or to find it for later treatment.
4.3.5 Lumbar Spine/Referred Pain
Muscles act as a target organ and their state of tension is modulated by electrical information from the motor component of the corresponding spinal nerve. Thus, the irritation of a spinal nerve root can cause an increase in muscle tone. 12 It is known that back injuries are very frequent in elite athletes, 18, 19 and lumbar pathologies such as a disk hernia at the L5/S1 level may present with hamstring and/or calf pain and limited flexibility, which may result in or mimic a muscle injury. 20 This is also known as “referred pain.” Subtle impingement of the lumbar nerve roots in the lumbosacral canal may, in fact, also be a factor in age-related predisposition to hamstring injuries ( ▶ Fig. 4.6). 3, 20
Although it is logical that a back-related muscle injury would require various forms of treatment, beyond simple treatment of those muscle–tendon injuries, 21 it could be argued that this is mainly a back problem, with a secondary muscular disorder. However, this secondary muscular disorder can prevent a player from training and competing and will require comprehensive treatment that addresses the primary problem, as well as facilitating the athlete’s return to sport. 22
Fig. 4.6 Lower back pain is very frequent in athletes.
Thus, differentiating between these disorders and others is important, not only because of the different pathogenesis, but also—more importantly—because of the different therapeutic implications. 23
Note: Athletes who undergo constant, intensive training have a higher incidence of degenerative disk disease and spondylolysis.
It is therefore important that the assessment of a muscle injury includes a thorough biomechanical evaluation, especially of the lumbar spine, pelvis, and sacrum. 23 Negative structural findings in the lumbar spine do not exclude nerve root irritation, and it should be remembered that lumbar dysfunctions, such as lumbar or iliosacral blocking, can also cause spine-related muscle injuries. 23 A diagnosis is established by means of a precise functional clinical examination. Spine-related muscle injuries are usually MRI negative, or the MRI reveals only a muscle edema. 20
If the lumbar spine is suspected of involvement in a muscle problem, a thorough physical examination of the lower back should be performed as follows:
The player should stand with his/her back to the examiner; an inspection will reveal if there is any (excessive) lordosis or scoliosis.
The paravertebral muscles should be palpated to assess if there is any pain, firmness, muscle asymmetry, hypertrophy, or hypotrophy.
The player should then be asked to bend forward, backward, and to both sides to reveal the range of motion of the lumbar spine and to see if there is any restriction of flexibility. The sacroiliac joint (SIJ) should be palpated if it is tender. Several tests can be used to reveal pelvis malrotation or a dysfunction of the SIJ. If necessary, a radiological examination should be undertaken (see ▶ Fig. 4.7).
Fig. 4.7 Typical spondylolysis of the fifth lumbar vertebra in a 22-year-old elite-level professional football player presenting with muscular problems in the hamstrings. Interestingly, there was no medical history of back problems.
Spondylolysis can cause muscular complaints, most commonly involving the hamstrings, owing to an increased kyphotic curve between L5 and S1, which causes an anterior shift in the center of gravity. This triggers a compensatory increase in hamstring tension to correct the pelvic tilt. The result is firmness and shortening of the hamstring muscles. Muscular complaints arising from spondylolysis and/or spondylolisthesis can successfully be managed conservatively in most cases ( ▶ Fig. 4.7).
Laboratory tests, such as testing for creatine kinase (CK), myoglobin (Mb), and lactate dehydrogenase (LDH), are of limited value when interpreting muscle injuries. CK and Mb levels are usually (highly) elevated after training stress. Tests are therefore not sensitive and specific enough to provide meaningful results ( ▶ Table 4.8). 3, 5
Possible functional spinal causes of muscular dysfunction
Possible structural spinal causes of muscular dysfunction
Locked sacroiliac or facet joint(s)
Real leg length difference
Functional leg length difference
Spinal and/or foraminal stenosis
Disk bulging and herniation
Imaging (whether an ultrasonography or MRI) provides additional information about muscle injuries and achieves various objectives, including the following:
Helping to locate the site of the injury.
Identifying defects/tears as well as showing their approximate size in the muscle tissue.
Indicating whether the tendon is involved.
MRI is particularly helpful in identifying whether an edema is present and in what pattern. However, even the best images do not reveal information about muscle tone, pain, functional loss, or previous injuries, etc. The spatial resolution of diagnostic ultrasonography is higher than that of MRI, whereas MRI offers better contrast resolution (e.g., to demonstrate a hematoma/edema).
Note: Imaging alone cannot offer an accurate diagnosis.
Ultrasonography is an important aspect of the diagnostic process for almost all muscle injuries, as it helps to locate the site of an injury and to exclude a higher grade of injury (i.e., a tear). Ultrasonography is usually easily available, allows dynamic examination, and is cost-effective, which makes it superior to MRI for follow-up examinations. However, it should be noted that ultrasonography of skeletal muscle requires a high level of skill on the part of the sports physician.
The procedure takes time, and familiarity with anatomy, and normal findings are essential for effective use of ultrasonography. With a little practice, the examiner can distinguish between a functional (nonstructural) muscle injury with no evidence of structural damage and a structural injury involving a tissue defect. Usually, ultrasonography helps to assess the need for further investigation by means of MRI.
It is advisable that clinical examiners experienced in ultrasonography review the results themselves, as any delegation of this assessment to radiologists or technicians could risk misinterpretation of the information.
It is recommended to use a 7.5- to 10.0-MHz transducer, starting with a transversal section. A complete scan through the muscle should be performed for the purposes of anatomical orientation. Any apparent abnormalities should be compared with the contralateral side. The transducer pressure should be as light as possible, since compressing the muscle may obscure smaller injuries. The longitudinal section is added in locations where a disturbance of the muscle structure or a gap is suspected ( ▶ Table 4.9). 24
For further treatment and/or to limit the field of view in subsequent MRI.
For injury characterization.
What is the size? And the prognostic consequence?
What is the size? Is needle aspiration possible/needed?
(Intramuscular or free tendon?)
What is the possible prognostic consequence?
Abbreviation: MRI, magnetic resonance imaging.
Some authors state that the best point in time for an ultrasonography is between 2 and 48 hours after the muscle trauma. 25 However, in some cases, where a dense, corpuscular hematoma obscures the defect in the first few hours after injury (see ▶ Fig. 4.8a–e), a follow-up may be needed to reveal the structural injury.
Fig. 4.8 (a) Hematoma echo-rich area longitudinal scans. (b) Hematoma echo-rich area transversal scans. (c) Hematoma retraction of the muscle fascicle longitudinal scans. (d) Hematoma retraction of the muscle fascicle transversal scan. (e) Sagittal section of a T2-weighted fat saturated image corresponding to (c).
(a,b) Ultrasonography 2 hours after an injury in an elite football player. A suspect area is visible (in a), owing to the corpuscular muscle hematoma (surrounded with –), but there is no obvious tear or retraction.
(c,d) Ultrasonography 12 hours later. The retraction of the muscle fascicle (–) is obvious, as is the tissue defect (*) in the muscle. The equivalent magnetic resonance (MR) image to (c) is shown in (d). It is obvious, that in this case, MRI offers no additional information compared to a good ultrasonography image.
(a) and (c) Longitudinal scans. (b) and (d) Transversal scans. (e) A sagittal section of a T2-weighted fat saturated image.