Strain to the quadriceps muscles may lead to quadriceps tendonitis and vice versa. Tendonitis or tendinopathy means the tendon attaches the quadriceps muscles to your patella, or the kneecap bone gets inflamed. The quadriceps muscles function to straighten the knee, enabling you to walk, jump, and climb stairs.

That is why in case of either conditions, strain or tendonitis of the quadriceps, everyday activities are disturbed.   

The condition arises due to repetitive movements that involve the knee joint as kneeling, jumping and so on. Overuse of the muscle results in micro-injury to the tendon, which gets inflamed, resulting in pain and swelling in the knee joint.

The injury is often associated with sports like volleyball and basketball.  Suddenly increasing your activity may cause a strain of the quadriceps tendon.

Anatomy of the quadriceps muscle and tendon

Quadriceps is short for the muscle quadriceps femoris. It is a massive muscle of the human body and acts as a flexor of the hip joint and an extensor of the knee joint. 

The quadriceps is not a single muscle; instead, it consists of four individual muscles. All of them form the main bulk of the thigh, being one of the most powerful muscles in the body. 

The four quadriceps are found in the anterior compartment of the thigh, and they include three vastus muscles and the rectus femoris muscles.

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

All of these muscles unite before reaching the knee joint and get attached to the kneecap bone, the patella. The patellar bone is attached to the leg bone, the tibia.  

All the vastus muscles extend the knee joint and stabilise the patella.

The Rectus Femoris muscle arises from the iliac bone in the hip and runs straight downwards to get attached to the patella via its tendon, the quadriceps femoris tendon.

The Rectus femoris is the only muscle that crosses two joints; the hip and the knee. That is why it can act on both of these joints; flexion of the thigh at the hip joint and extension at the knee joint.

Causes of quadriceps strain and tendonitis

Quadriceps plays a vital role in everyday activity as well as in sports. However, it faces stress and faces injuries quite often. Such injuries to the muscles and tendons are painful and debilitating.

Three mechanisms are involved in a quadriceps strain that results in acute injury causing macro-trauma. These include;

• Sudden slowing down of the leg while in motion as it happens in kicking
• Forceful contraction of the quadriceps as in sprinting
• A rapid deceleration of an overstretched quadriceps as occurs in a quick change of direction

The rectus femoris crosses two joints which makes it more vulnerable to strain and tendonitis. The most common sites of strains occur in the muscle itself and the junction where the muscle gives rise to its tendon. This is usually just above the knee, including both the distal and proximal muscle tendon.

A quadriceps muscle strain is usually due to an acute muscle stretch, which happens simultaneously with a forceful contraction.  The muscle may also be overloaded by repeated eccentric muscle contractions of the knee extensor muscles.

People who play sports like rugby and football are at high risk of acute quadriceps muscle strain injury. Such sports involve sudden forceful eccentric contraction of the quadriceps during knee flexion and hip extension.

Muscle strain can also be caused by excessive passive stretching or activation of a maximally stretched muscle.  

Overuse of muscle and muscle fatigue is the most prevalent cause of quadriceps tendonitis. Repeated movement of the thigh and knee causes the tedious functional load, like in many sports, leading to small tears.

Some other causes of quadriceps strain and tendonitis include;

• Sports trauma like an acute tearing injury
• Trauma acquired during jumping on a hard surface
• A sudden increase in physical activity
• Poor posture
• Poor walking habits

Certain risk factors increase the risk of quads strain and tendonitis. Athletes are especially prone to quads injuries. This is particularly true if;

• You have to run on hard surfaces
• You play jumping sports, like volleyball and basketball
• You do exercise without warming up
• You perform an exercise without recovery time
• You have to repeatedly squat or kneel

Aging, obesity, tight muscles (hamstrings and quads) gradually increase the pressure on your tendons. Similarly, muscular imbalances in the hip and thigh also increase the pressure on one leg and cause strain and tendonitis.

Signs and symptoms of quadriceps strain and tendonitis

There are three grades of quadriceps muscle strain;

Symptoms of grade 1 injury

The grade 1 injury is mild and not severe enough to stop activity at the time of injury.

• A cramp in the thigh
• A general feeling of tightness in the thigh
• Mild discomfort on walking
• Running is difficult
• No swelling
• A lump or area of spasm at the site of injury

Symptoms of grade 2 injury

The injury is painful enough to continue with activity impossible.

• Sudden sharp pain in the front of the thigh while running, jumping or kicking
• Walking is difficult
• Swelling or mild bruising at the site of injury
• The front of the thigh is tender to touch
• Pain on straightening the knee against resistance
• Inability to fully bend the knee

Symptoms of Grade 3 injury

The symptoms are severe enough to limit movement for six to twelve weeks.

• Severe and sharp pain that occurs suddenly pain in the front of the thigh
• Inability to walk without any support like crutches
• Swelling in front of thigh appears immediately
• Significant bruising within 24 hours at the site of injury
• Painful passive muscle contraction
• A visible bulge in the muscle

The symptoms of quadriceps tendinitis gradually develop over time. These include;

• Dull pain in the front of your knee, just above the kneecap.
• Pain has a history of worsening over time
• Pain gets worse after extended sitting or with activities like jumping, squatting, and running
• Rarely, the pain resolves during activity and comes back during inactivity
• Stiffness in the thigh, especially in the morning
• Swelling may be present
• The affected area is tender to touch
• Weakness of thigh muscles
• Limit range of motion and poor mobility

Diagnosis of quadriceps tendinitis and strain

The history and nature of presenting complaints indicate the injury, whether muscle or tendonitis. Various tests help to confirm the diagnosis.

Physical examination and radiological imaging techniques are used to differentiate between the two conditions. MRI can give a complete picture of quadriceps tendons.

Treatment of quadriceps strain and tendonitis

Conservative treatment is adopted for managing the pain of an acute injury or chronic tendonitis. Physical rehabilitation always follows conservative and surgical treatment. 

1. Immediately after the injury to first few days

1. RICER

Muscle strain and tendonitis require rest, and a break from any sports or other activities should be employed to reduce further damage.

The application of ice and compression immediately after an injury helps reduce swelling. It also helps to reduce the hematoma formation (blood clot) in the muscle in acute muscle strain.

Elevation also cuts back swelling in the tissue spaces, thereby preserving the blood circulation and preventing ischemia in the muscular tissue.  Wearing a knee brace may be necessary in some cases to stabilise the patella and support the knee joint. 

Application of K-tape helps to ease off the stress in case of tendonitis. Athletic tapes also help to support and stabilise the kneecap.

In case of an acute injury of quadriceps muscle strain, immediate care is essential.

Besides rest and ice application, immobilising the position of the knee joint is very important.

The affected knee should be placed in 120° of flexion using a hinged knee brace or elastic compression wrap.  If the knee is left in an extended position, the muscle will start healing in a shortened position and cause more pain after healing.

The immobilisation in flexion position also helps to;

• Avoid potential muscle spasms
• Reduce the risk of intramuscular bleeding
• Minimise the risk of developing myositis ossificans

Resting the joint should be carried out only for few days, after which gradual movements should be initiated to reduce scar formation.

Refer to a specialist for the injury to be evaluated as soon as possible.

• Medication

Over-the-counter analgesics help resolve the pain and inflammatory changes.

NSAIDs in the initial 48-72 hours of an acute muscle strain are beneficial for pain management.

In cases of tendonitis, corticosteroid injections help speed recovery.

• TENS

Application of TENS helps relieve the pain, but it should be applied if no visible swelling or bruising is present.

• Surgery

For quadriceps tendonitis, surgical repair is taken up if conservative treatment fails. It involves the removal of the damaged portion of the quads tendon.

This may be done via open surgery or by a less invasive arthroscopic procedure done with small incisions, a tiny video camera, and mini surgical instruments.

Another procedure called percutaneous ultrasonic tendon debridement involves using ultrasonic energy to remove damaged tissue accumulated in the joint space and around the tendon in case of tendonitis.

Surgical repair is also a must in cases of third-grade muscle strain of quads. Some other indications for surgery in case of quads strain to include;

• Extensive bleeding inside the muscle with the presence of large hematoma (collection of blood)
• Tear of a rectus femoris with few or no agonist vastus muscles
• Injury of the second degree with more than half of the muscle belly tear
• Persisting muscle pain lasting for more than 4-6 months in a previously injured muscle, especially with extension deficit (surgical debridement of scar tissue that requires removal of adhesions)

Hyperbaric oxygen therapy is a technique that, if applied during the early phase of muscle strain and injury, can help speed recovery and healing.

• After few weeks, when the muscle starts to recover

• Massage

A thigh massage targets quadriceps muscles involving a range of different techniques. These help to reduce muscle tightness, relieve pain and increase blood circulation.

A thigh massage also cuts back at scar and adhesion formation in the thigh, which is essential for preserving range of motion and flexibility later on. It is of great benefit for a person being treated to return to sports or exercise.

Various techniques included during a thigh massage are;

• Effleurage
• Kneading
• Frictions
• Wringing
• Therapeutic ultrasound

Therapeutic ultrasound also contributes to lessen scar formation and adhesions of thigh muscles post-injury.

In tendonitis, ultrasound therapy helps to speed up healing and cuts back at the recovery time.

Any lingering pain in the thigh is also effectively addressed via ultrasound.

• Active rehabilitation

Stretching and strengthening exercises are of utmost importance to preserve the function of quads muscle, in either case of muscle strain and tendonitis. These include activities that work on the hamstrings and hips and support the knee tendons, including the quads.

A brief introduction to physical exercises according to the post-injury phase of muscle strain include;

1. Within the first 24-48 hours
2. Ankle pumps
3. Isometric quadriceps sets
4. Hamstring sets
5. Glut sets
6. Staring week three to twelve
7. Isometrics with quadriceps contractions
8. Straight leg raises
9. Isotonic exercises beginning with the lightest free weights
10. Terminal knee extensions
11. Addition of more free weights
12. Isokinetic exercises
13. Conditioning exercises like upper body workouts, swimming, treadmill walking
14. After twelve weeks
15. postural control exercises and progressive speed eccentric moves 
16. higher velocity eccentric sports-specific activities, for example, squat jumps, split jumps, single leg bounding, backward skips, single and double leg deadlifts, and split stance deadlift, and so on.

Stretching exercises for quads

Stretching exercises should be done carefully till the point of discomfort with no pain.

Static quad stretch

• Either stand or lay on your front.
• Take support from a chair if standing and pull the affected leg towards the buttock by holding it from the foot.
• A gentle stretch should be felt on the front of your thigh.
• Hold the stretch for 20-30 seconds.
• Switch sides and do the same with the opposite leg.
• Repeat at least three times on each side.
• Perform the exercise at least three times a day.

Hip flexor stretch

• Kneel on the floor on the healthy side.
• Place the other affected foot out in front. Bend its knee.  
• Keep your back straight.
• Push your hips forwards.
• Your bent hip and knee and hip should feel a stretch at the front.  
• Hold the stretch for thirty seconds.
• Repeat on the other side as well.
• Perform the stretch at least three times a day.

Strengthening exercises

Strengthening exercises help to increase the load that is put through a muscle gradually. Low-level strengthening exercises can be started as early as day five.

A physical therapist may start with isometric or static exercises before progressing to dynamic resistance exercises. Sports specific running and sprint drills are taken up later in the rehabilitative stage.

Straight leg raises

• Sit flat on the floor. Spread your legs out in front. 
• Start by slowly raising one leg off the floor. Make sure to keep the knee straight.  
• Hold for few seconds.
• Lower back your leg to the ground.
• Repeat at least 10 to 20 times.
• Switch sides and do the same with the opposite leg.

Step-ups

• Start with a box height or a stair that is comfortable for you. 
• Be sure to align your knee with your toes.
• Step up the box or stair.
• Keep your pelvis levelled and your knee in alignment.
• Engage the muscles of the buttocks.  
• Fully lock out the knee.
• Return down to the ground, slowly taking more time than steeping up.
• Perform at least two sets each of 15-20 reps every day.

Prevention of quadriceps tendonitis and strain

Proper warm-up and cool-down procedure should be followed after exercise or sports activity.

The use of orthotics helps some chronic cases. They are shoe inserts the support the foot and help manage the pain of tendonitis by reducing the pressure on your knee tendons.