A pain in the thigh : what all athletes should know about quad strains

Quadriceps strains in sport are surprisingly common, but what are the symptoms, how can they be diagnosed and what are the treatment options? SPB looks at the evidence

Strains (tears) and contusions (impact injuries) of the quadriceps muscles of the frontal thigh are common in sport and frequently result in lost time from training and competition. Sudden-onset strain injuries of the quadriceps commonly occur in sports such as soccer, rugby, and football - all of which require sudden forceful eccentric contraction of the quadriceps during regulation of knee flexion and hip extension. In short, these muscles are particularly vulnerable during landing or deceleration, but can also be injured during powerful explosive contractions such as squats or jumps.

How common are quadriceps strains?

In an extremely comprehensive study, researchers examined the rates and patterns of quadriceps strains in student-athletes in the National Collegiate Athletic Association (NCAA)⁽¹⁾. Data was gathered from college students participating in 25 different sports during the period 2009-2015. The key findings were as follows:

• The overall quadriceps injury rate was 1.07 per 10 ,000 athlete-exposures (AEs).
• The sports with the highest overall quadriceps strain rates were women's soccer (5.67/10, 000 AEs), men's soccer (2.52/10, 000 AEs), women's indoor track (2.24/10, 000 AEs), and women's softball (2.12/10, 000 AEs).
• Across sex-comparable sports, women had a higher rate of quadriceps strains than men overall (1.97 versus 0.65/10, 000 AEs).
• The majority of quadriceps strains were sustained during practice (77.8%). However, the quadriceps strain rate was higher during competition (where effort levels tend to be highest) than during practice sessions.
• Most quadriceps strains occurred in the preseason period (57.8%), and rates were higher during the preseason compared with the regular season.
• Most of the injuries were non-contact injuries (63.2%), while overuse injuries (ie quad strains that came on chronically) accounted for 21.9% of the total.

Together, these findings suggest that female athletes whose sports include explosive-type or vigorous eccentric contractions and who are in a less well-conditioned state of fitness (eg during the pre-season) are particularly at risk of quadriceps strain.

Understanding quadriceps anatomy

The quadriceps muscle group is actually composed of four distinct muscle bellies (see figures 1-3). These are:

• The rectus femoris (RF), which spans the front most portion of the thigh.
• The vastus medialis (VM) and vastus lateralis (VL), which span the inner and outer portions of the thigh respectively.
• The vastus intermedius (VI), which runs ‘underneath’ these muscles.

At the ‘top end’ (more technically known as proximal) of the quads, the three vastus muscles originate from the anterior (front), medial (inner), and lateral (outer) aspects of the femur – the large thigh bone. The RF originates from a region of the pelvis known as the ‘anterior inferior iliac spine (AIIS), and has three tendons that connect the RF muscle to the pelvis (see figure 3)⁽²⁾. At the lower (distal) end, the four muscle bellies converge to form the thick quadriceps tendon, which inserts into the top of the patella (knee cap). This thick tendon is composed of multiple layers from each individual muscle group positioned one on top of the other.

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Figure 1: Anatomy of quadriceps anterior (front) view

Diagram shows right leg as seen from the front. VL = vastus lateralis; VI = vasto intermedius; VM = vastus medialis; RF = rectus femoris. The VI muscle lies underneath the RF muscle.

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Figure 2: Anatomy of the quadriceps muscle (cross section view)

The same leg viewed as a ‘slice through’. NB: femore = femur bone.

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Figure 3: Anatomy of the proximal rectus femoris

The red arrow shows direct tendon and its insertion on the anteroinferior iliac spine of the pelvis; the two black arrows show the two smaller indirect tendons and their insertion locations on the pelvis.

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How do quadriceps strains occur?

There are a number of factors that increase the risk of a quadriceps strain. For example, high loadings combined with an eccentric contraction (when muscles lengthen under load) can lead to strain injury. Excessive passive stretching or a contraction of an already maximally stretched muscle can also cause a strain. Muscle fatigue has also been shown to play a role in acute muscle injury, increasing the risk⁽³⁾. This may account for the observation of increased injury risk during the pre-season (when fitness levels tend to be lower, leading to the earlier onset of fatigue). However, of the four muscle bellies, it is the RF is most frequently strained^(4-8). There are a number of factors behind the increased vulnerability of RF; as well as crossing two joints (hip and knee), the RF muscle contains a high percentage of explosive ‘type-II fibres’, and also has a more complex manner of tendon insertions, all of which are known to increase injury risk^(9,10).

As noted in the NCAA study above, a quad muscle strain occurs for the most part as a result of eccentric contractions^(4,11). This can occur, for example, when soccer or rugby players unexpectedly encounter irregular or slippery turf as they are about to kick a ball. As a result, they may miscalculate the position or speed of the ball and try to compensate for their error by extending the hip. The muscle at risk in this situation is the RF, more specifically the uppermost (proximal) third of the RF.

This type of injury can also occur when athletes lose their footing during abrupt deceleration – something that is common in all sports that involve running. In some cases, a strain can involve the tendon of the RF, which arises from the acetabular rim (top black arrow, figure 3). These strains or lesions may mimic hip pain and athletes often report that they have the sensation that ‘something in the hip’ has been displaced during an incident. Typically, they will complain of pain in the region of the tensor fascia lata, a muscle that runs across the hip, even though the pain originates not from the tensor fascia lata but from the RF tendon.

Diagnosing a quadriceps strain

The diagnosis of a quadriceps strain and/or contusion requires knowledge of the athlete’s exercise history together with a physical examination by a physiotherapist or other health professional. Imaging such as ultrasound or MRI scans may also be needed in cases where the diagnosis is uncertain or where further detail is required regarding the type and location of the muscle strain.

• Exercise history – Athletes who suffer an acute quadriceps strain will usually know right away. Typically, a sharp pain is felt, associated with a loss in function of the quadriceps. However, in some instances, the pain may come on gradually, only to be felt fully at the end of a game or practice session. As well as the pain, there may be some swelling and loss of motion. Although pain can be experienced anywhere along the quadriceps, it is typically reported either in the distal portion of the rectus femoris (ie above the knee) or in proximal portion of the rectus femoris (top of the center of the thigh)^(4,5).
• Physical examination – When a quad strain is suspected, a thorough examination by a physiotherapist is needed. This will involve feeling around (palpating) the area, strength testing, and an assessment of any loss of motion. Strain injuries of the quadriceps may present with an obvious deformity such as a selling, bulge or defect in the muscle belly. However bleeding under the skin leading to swelling may not develop until 24 hours after the actual injury. Clinicians will typically feel along the entire length of the injured muscle, trying to locate the area of maximum tenderness and feeling for any defects in the muscle. This is usually followed by strength testing, which includes seeing how well the athlete can push against resisted knee extension (leg straightening) and hip flexion (pushing the leg backwards behind the line of the body). To test RF function, knee extension testing should be carried out with the hip both flexed and extended. Assessing the degree of tenderness, the presence and degree of any swelling, and how much strength/muscle function is affected, allows the physio to determine the grading of the injury, which helps provide direction for further diagnostic testing and treatment (see box 1).

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Box 1: Grading a quadriceps strain

 There are a number of ways of clinically grading muscle strains in the literature^(9,12). The use of a grading system is helpful for clinicians as it helps provide guidance for treatment and rehabilitation, and eventual return to sport.

Grade	Muscle pathology	Clinical symptoms
I	Minor tearing of muscle fibers with only minimal or no loss in strength.	Pain is usually mild to moderate with no palpable defect in the muscle tissue on examination.
II	More severe disruption to the muscle fibers with significant pain and loss of strength.	A defect in the muscle tissue may sometimes be felt.
III	Complete tearing of the muscle with associated severe pain and complete loss of strength.	A palpable defect in the muscle tissue can frequently be felt, especially if examined at onset of injury prior to hematoma (swelling) formation.

Diagnosis of quadriceps injury caused by a direct blow (contusion)

A direct blow to the quadriceps can cause significant muscle damage, leading to a contusion. Typically, a contusion involves rupture to the muscle fibers at, or directly adjacent to, the area of impact. This usually leads to a swelling within the muscle causing pain and loss of motion. A contracted muscle will absorb force better and result in a less severe injury than a relaxed muscle⁽¹³⁾ – something that can provide useful context for clinicians taking a history.

• Exercise history - Athletes usually report a definite impact mechanism associated with a contusion injury such as a direct blow from an opponent’s knee or other piece of equipment. This information is important for differentiating strain and contusion injuries. Athletes also typically report localized pain at the site of injury, swelling, decreased range of motion, and tenderness. Depending on the severity of injury, some athletes may be able to continue their activity, only seeking treatment after competition or training.
• Physical examination - Upon examination, clinicians will look for any obvious signs of deformity, swelling, or bleeding under the skin (ecchymosis). Feeling along the injured muscle can help localize the exact site of muscle damage and determine if there is any associated injury. Strength testing of the quadriceps should assess resisted knee extension and hip flexion; by comparing the findings to those of the uninjured leg, the severity of injury can be determined (see box 2).

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Box 2: Grading contusion injury severity

 The measurement of knee flexion can be used as a prognostic indicator in quadriceps contusions. Jackson and Feagin originally described a classification system, which was further modified by Ryan et al and is shown below^(14,15).

Grade	Symptoms	Clinical observations
Mild	Localised tenderness	Normal walking and running gait; knee can be bent more than 90 degrees.
Moderate	Signs of swelling with a tender mass in the quadriceps	Walking and running gait is moderately affected; knee of injured leg can only be bent 45–90 degrees maximum.
Severe	Very noticeably swollen, with a tender mass in the quadriceps	Severely affected walking and running gait; knee can be bent by no more than 45 degrees.

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Is imaging needed?

Most strain injuries to the quadriceps can be diagnosed with history taking from the athletes and a thorough examination. However, imaging in the form of ultrasound or MRI may be needed where the diagnosis is uncertain or further detail is needed regarding the type and location of the muscle strain – for example small, partial tears or for estimating the size of a tear. Imaging may also be particularly important to rule out an injury to the bone where the tendon attaches - technically known as an avulsion injury. An avulsion injury can be career ending if not diagnosed and treated correctly.

• Ultrasonography - is widely used because it’s cheap and quick. It can also be used for dynamic studies of the muscle during contraction and relaxation, and if doubts arise, scans can easily be obtained of the uninjured les muscle for comparison purposes. The caveat is that ultrasound requires a skilled and experienced clinician to obtain the best results^(16,17).
• Magnetic resonance imaging (MRI) - is also an excellent imaging technique that can simultaneously assess of muscle, joint, and bone planes. However, it generally remains a second-choice technique due to its high cost and relatively low availability. Also, It can sometimes be difficult to distinguish between muscular contusion and strain on MRI, which simply re-enforces the importance of a thorough initial clinical history and examination by a skilled sports clinician^(18,19).

For contusions, imaging is typically not necessary, but can be helpful in a few instances – for example if an athlete develops front thigh pain without a known mechanism of injury. If this is the case, imaging can provide additional information regarding the nature of muscle injury, and help differentiate between strain, contusion, or avulsion injuries⁽¹⁸⁾.

Managing and rehabilitation of a quadriceps injury

The key to successful treatment and rehab of a quad strain is an early and accurate diagnosis. The good news for athletes is that most quadriceps muscle injuries when managed correctly heal conservatively – ie without the need to surgical intervention^(20,21). Quad strain treatment follows the general principles of other muscle injury treatments and can be roughly divided into three phases⁽²²⁾:

1. Degeneration of muscle fibers that happens during the inflammation phase (1–3 days).
2. Regeneration of muscle fibers (3–4 weeks).
3. Maturation and strengthening of muscle fibers during the remodeling phase (3–6 months).

The length of these phases will of course depend on the severity (grading) of the quad strain injury. Immediately following a quad injury, athletes will experience varying degree of pain and discomfort (depending on the extent of the injury), and during this time should adhere to the P-R-I-C-E protocol consisting of Protection, Rest, Ice, Compression and Elevation. Also, controlled (ie limiting) loading of the affected muscle will help to minimize the extent of the injury and the size of any swelling.

After the acute stage has passed and the pain has relented, PAIN-FREE active and passive stretching should be started with gentle isometric and eccentric contractions. Once pain-free full range of movement and isometric contractions can be achieved, the rehabilitation process can be taken up a notch with a move to gym-based exercises. Here, the loading can be gradually increased in a controlled and safe manner. The key as always is to achieve gradually increased loading without any reoccurrence of pain.

Once the level of leg strength achieved in the gym is approaching pre-injury levels, it’s time for functional, ‘return to sport’ training. During this period however, the gym work remains and loadings are increased further. It’s important to understand that a return to full training represents a significant step up in loading from gym training. Therefore, the field tests such as the Illinois Agility Test and the Sprint Braking Test are recommended prior to a resumption of full training following quadriceps injury:

• Illinois Agility Test –
  (table 1 shows norms for this test).
• Sprint Braking test – the purpose of this test is to quantify in an objective manner the effectiveness of the contraction of the quadriceps muscles during the braking phase. Following a preliminary test consisting a maximal sprint for 30 meters, the athlete is asked to make a sprint over the same distance at 90% of the maximum speed recorded during the preliminary test and to stop at the level of a skittle placed at a determined distance from the end of the sprint. The protocol provides for three tests, the first of which the stop-skittle is placed at 8 meters, and the second and the third respectively at 6 and 4 meters from the end of the sprint.

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Illinois Agility Test Norms

Here is an example table giving ratings scores from poor to excellent for males and females at national level sport in the 16-19 year old age range.

Rating	Males (seconds)	Females (seconds)
Excellent	< 15.2	< 17.0
Above Average	15.2 - 16.1	17.0 - 17.9
Average	16.2 - 18.1	18.0 - 21.7
Below Average	18.2 - 19.3	21.8 - 23.0
Poor	> 19.3	> 23.0

Data from: Davis B. et al; Physical Education and the Study of Sport; 2000.

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In the final stage of rehab, sports training should be introduced gradually with fewer, shorter sessions initially allowing more time for recovery. Over time, training sessions can be brought up to pre-injury levels. Assuming these can sustained over a period of weeks, without any adverse effects, the athlete will be ready to return to full competitive sport with fully rehabilitated quadriceps muscles!

References

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