Quadriceps Muscle Strain

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We looked after information on different databases like Web of Science, PubMed, PEDro, Web of Knowledge, etc. The keywords that we used were quadriceps muscle strain, muscle strain, quadriceps strain, quadriceps strain therapy, quadriceps injury, muscle injury, etc.

Definition/Description

A quadriceps muscle strain is an acute tearing injury of the quadriceps,more specific a partial tear of the small fibers of the muscles that make up the quadriceps group. This injury is usually due to an acute stretch of the muscle often at the same time of a forceful contraction or repetitive functional overloading. The quadriceps which consists of four parts, can be overloaded by repeated eccentric muscle contractions of the knee extensor mechanism. When the muscle is elongated by an eccentric contraction, high muscle forces are generated during the elongation and added to the forces produced by the passive connective tissue so it almost certainly induces a muscle strain injury. This force is several times higher than the force produced during a maximal isometric contraction.

Clinically Relevant Anatomy

There are generally three mechanisms for quadriceps strain. 1. Sudden deceleration of the leg (kicking), 2. violent contraction of the quadriceps (sprinting) and 3. rapid deceleration of an overstretched muscle (by quickly change of direction).

The quadriceps femoris acts as a hip flexor and knee extender. This muscle is composed of 4 subcomponents:

• Rectus femoris
  
• -Vastus medialis
  
• -Vastus lateralis
  
• Vastus intermedius

The rectus femoris originates at the ilium, thus crossing both the hip and knee joint along its course. The remaining muscles originate on the femur. These four muscles are innervated by the femoral nerve.

These four muscles come together in the quadriceps tendon and insert to the base of the patella.
The true insertion of the quadriceps femoris is into the tibial tubercle, but convention considers it as inserting into the patella through the quadriceps tendon or the suprapatellar tendon. The part distal to the sesamoid bone is known as the patellar ligament (ligamentum patellae), patellar tendon, or infrapatellar tendon.

The Rectus femoris is the only part of the muscle participating in both flexion of the hip and extension of the knee.  The other 3 parts are only involved in the extension of the knee. The rectus femoris is the most superficial part of the quadriceps and it crosses both the hip and knee joints. So it is more susceptible to stretch-induced strain injuries.  The most common sites of strains are the muscle tendon junction just above the knee (both distal and proximal but most frequently at the distal muscle-tendon) and in the muscle itself.

Muscle functions:
-Rectus Femoris: Hip flexion, Knee extension
-Vastus Lateralis: Knee extension
-Vastus Intermedius: Knee extension
-Vastus Medialis: Knee extension
-Semitendinosus: Hip extension, Knee flexion
-Semimembranosus: Hip extension, Knee flexion
-Biceps Femoris: Hip extension, Knee flexion

Epidemiology/ Etiology

There are generally three mechanisms for quadriceps strain.

1. Sudden deceleration of the leg (kicking),
2. violent contraction of the quadriceps (sprinting) and
3. rapid deceleration of an overstretched muscle (by quickly change of direction).

The most commonly strained quadriceps muscle is the M. Rectus Femoris, because he crosses two joints and has a high proportion of type 2 fibers. 

The strongest risk factor for developing a quadriceps muscle strain injury is a recent history of muscle strains. The next strongest risk factor in line is a past history of a quadriceps muscle strain. Other risk factors for this injury may include low muscle strength, an imbalance between the quadriceps and the hamstrings, limited flexibility, muscle fatigue, a poor technique, a high percentage of Type II fibers in the muscle, and so on. Another possible cause of strain injury can be a bad warming-up before an exercise or no warming-up at all. The majority of quadriceps strains (incurred by kicking sports) are located in the dominant leg, because it is the preferred kicking leg which is used more often.

Characteristics/Clinical Presentation

Typically a muscle strain is characterized by a violent muscle contraction occurring simultaneously with an excessively forced stretch. The vast majority of muscle strains involve muscles that pass over two joints or more or occur in muscles with complex architecture (Brewer 1962). In the anterior thigh the rectus femoris is most vulnerable to strains.

Various ways of grading muscle strains have been proposed. Factoring in pain, loss of strength, and physical exam findings in a grading system helps provide guidance for treatment, rehabilitation, and eventual return to play. The table below provides an outline of a clinical grading system for muscle strains.

• Grade 1 strains represent 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 exam.
  
• Grade 2 strains involve more severe disruption to the muscle fibers with significant pain and loss of strength. A defect in the muscle tissue may sometimes be felt. 
• Grade 3 strains are a result of 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 formation. 

Although most of the times trauma history is associated, evaluation methods can be used to identify the strained muscle.

Examples of evaluation methods:

• Hamstrings/Quadriceps ratio (H : Q)
• Range of motion (ROM) and End-feel
• Muscle strengh
• Skin temperature
• Pain(while flexing, stretching or using the muscles)
• Muscle spasms
• Swelling
• Bruises, if the blood vessels are broken/damaged
  
  

Differential Diagnosis

• Contusion
• Jumper's Knee
• Femoral Neck Stress Fracture
• Slipped Capital Femoral Epiphysis

Diagnostic procedures

Most acute injuries in the quadriceps muscles can be found easily by the therapist by just letting the patient tell how the injury occurred and doing a quick examination of the quadriceps muscles afterwards. But when the therapist isn’t too sure, he can always consider medical imaging to give a definite answer. Medical imaging tells us for example the exact type and location of the muscle strain.

After obtaining a thorough history, a careful examination should ensue including observation, palpation, strength testing, and evaluation of motion. Strain injuries of the quadriceps may present with an obvious deformity such as a bulge or defect in the muscle belly. Ecchymosis may not develop until 24 h after the injury. Palpation of the anterior thigh should include the length of the injured muscle, locating the area of maximal tenderness and feeling for any defect in the muscle. Strength testing of the quadriceps should include resistance of knee extension and hip flexion. Adequate strength testing of the rectus femoris must include resisted knee extension with the hip flexed and extended. Practically, this is best accomplished by evaluating the patient in both a sitting and prone-lying position. The prone-lying position also allows for optimum assessment of quadriceps motion and flexibility. Pain is typically felt by the patient with resisted muscle activation, passive stretching, and direct palpation over the muscle strain. Assessing tenderness, any palpable defect, and strength at the onset of muscle injury will determine grading of the injury and provide direction for further diagnostic testing and treatment. 

There are several types of medical imaging which can be used for muscle strains:

• Radiographs: a positive point about radiographs is that they are good to differentiate the etiology of the pain in the quadriceps muscles. Etiologies can be muscular (muscle strain etc.) or bony (stress fracture etc.).
• Ultrasound (US): Ultrasound is very often used because it is relatively inexpensive. But it also has a quite big disadvantage, namely the fact that it’s highly operator dependent and requires a skilled and experienced clinician. Another advantage of US is the fact that it has the ability to image the muscles dynamically and to asses for bleedings and hematoma formation via Doppler.
• Magnetic resonance imaging (MRi): Mri Is a good way to give detailed images of the muscle injury. If it’s not clear on the Mri images whether it’s a contusion or a strain, the therapist must rely on the story the patient told him about how the injury occurred. And then he can deduce whether it’s the one or the other.

Outcome measures

A significant evidence of a reduction in swelling with ice and simultaneous exercises in comparison with thermotherapy has been found by Bleakley c et al. Another trial found that continuous ice application led to statistically significant reductions in pain.

A group of quadriceps injuries received treatment with application of a maximum compression bandage was compared to a control group where subjects were treated with rest and elevation only. No significant differences in time to complete subjective recovery were noted by Thorsson O. et al. 

Examination

Its often present:

• Tenderness provoked by direct palpation at the injury site.
• Pain during resisted extension
  
• Ely's test

An examination should include observation, palpation, strength testing and evaluation of the range of motion (ROM). When we are testing the strength of the muscle, this must happen with resisted knee extension with the hip both flexed and extended. And as mentioned above, this will result in pain when the muscle is damaged. When the muscle is damaged, the patient will also feel pain while the muscle is passively stretched. When the examination is done, the therapist will be able to determine the grading of the injury. When the examination isn’t clear enough, we can use medical imaging to give the decisive answer. Palpation of the anterior thigh should include the length of the injured muscle, locating the area of maximal tenderness and feeling for any defect in the muscle.

Medical Management

The use of NSAID's ( nonsteroidal anti-inflammatory drugs) is still contorversial, their benefit, cost and potential adverse effects may be taken into consideration. If used, it should be during the inflamatory period (48h-72h) 

Surgical Intervention may be necessary if there is a complete quadriceps muscle rupture.

There has been an experimental study (1998) about the use of hyperbaric oxygen therapy. The therapy should be applied during the early phase of the repair of the injured muscle.
This therapy could accelerate the repair of the injured muscle.
But we should be careful to extend these findings to clinical practice, because there haven’t been any clinical studies to show the beneficial effects of this therapy in the treatment of muscle or other types of soft tissue injuries in athletes yet.

Physical Therapy Management

When a quadriceps muscle strain occurs during a competition or training, it is important to react immediately. In the 10 minutes following the trauma one needs to put the knee of the affected leg immediately in 120° of flexion. This avoids potential muscle spasms, reduces the hemorrhage and minimizes the risk of developing myositis ossificans

If the knee is left in extension the healing process will be slower and more painful because the quadriceps will start to heal in a shortened position. The rest of the therapy during the healing process is based on the RICE therapy. This includes:

1. Rest,
2. Ice treatment for 20 minutes every 2-3 hours,
3. Compression with an ACE bandage
4. Elevation.

This hasn’t been proved in scientific literature, but it is commonly used by physiotherapists and doctors. Before a patient turn back to normal activities, he or she should do some exercises and stretching to reinforce the quadriceps and hamstrings- muscle. The exercises can be isometric, isotonic, isokinetic and in a later stage of the revalidation sport- or ADL-specific. An overview of the types of exercises:

• isometric: muscle contraction without change in muscle length (mostly against a fixed object).
• isotonic: muscle contraction against a constant resistance with a shortening/lengthening of the muscle.
• isokinetic: muscle contraction by a specific movement (e.g. flexion-extension of the knee).

All of these exercises should be done in a range of motion that is pain-free. These strengthening exercises will also help in preventing from a new strain injury.

Recent Related Research (from Pubmed)

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