Hip flexors lie in front of hip joint. Hip flexors are group of muscles also known as hip joint flexors. The contraction of hip flexor muscles causes flexion of hip joint.
Following muscles are grouped as hip flexor-
- Psoas muscle
- Iliacus muscle
- Rectus femoris muscle
- Sartorius muscle
- Pectinius muscle
- Gracilis muscle
- Tensor fascia lata
- Adductor brevis muscle
- Adductor locus muscle
The hip flexors help in bending the hip joint while performing various activities that involves lower leg. Most common cause of hip flexor strain is sport injury.1 The flexor muscles are specifically active while kicking and sprinting.2 Hip flexor strain is also known as psoas strain syndrome,1 hip flexor tear, hip flexor injury, iliopsoas strain, pulled hip flexor, torn iliopsoas muscle and stained iliopsoas muscle. A hip flexor strain is characterized by tearing of one or more than one of hip flexor muscles. The condition results in pain that is mostly concentrated over groin.
Which Hip Flexor Muscle Frequently Causes Hip Flexor Sprain?
The most frequently affected muscle in hip flexor strain is iliopsoas muscle. The iliopsoas muscle begins from the lower back and pelvis and inserts into the femur.
Types of Hip Flexor Strain
The hip flexor strain can broadly be classified into three types depending upon the condition of the injury.
- Grade 1 tear
- Grade 2 tear and
- Grade 3 tear
Grade 1 Tear- Grade 1 Hip Flexor Strain occurs only in small number of fibers which is associated with mild pain, but this does not affect the functional ability.
Grade 2 Tear- Grade 2 Hip Flexor Strain involves tear in several muscle fibers, which is also associated with moderate loss of function. The majority of hip flexor strains are grade 2 strains.
Grade 3 Tear- Grade 3 Hip Flexor Strain results in complete rupturing of all or most muscle fibers, which is associated with major loss of function.
Risk Factors of Hip Flexor Strain
- Over use of untrained muscle
- Inadequate warm up
- Poor posture
- Poor biomechanics and
- Muscle fatigue.
- Overuse of Untrained Muscle Results In Hip Muscle Strain – Flexor muscle strain is observed in non-professional individual who decide to walk 1 to 3 miles. The muscles are not trained and repeated contraction of untrained muscles results in hip flexor strain. Such injury is observed in individual who participate in marathon running or long distance biking.
- Inadequate Warm Up Results In Hip Muscle Strain- Athlete well trained must warm up prior to starting prolonged use of muscles. Individual participating in long distance running, cycling and contact sports must warm up before competition or participation to prevent muscle tear.
- Poor Posture Results in Hip Muscle Strain- Normal or correct posture is important to prevent muscle injury and tear. Poor posture leads to bad ergonomics and imbalance of muscle coordination. Poor posture often results in over or under use of group of muscles. If individual tries to sprint or performs vigorous activities weaker muscle may tear. Individual working as security guard or standing for several hours at work may maintain poor posture for several months resulting in weakness of group of flexor muscles.
Poor Biomechanics Results In Hip Muscle Strain- The joint movements like flexion, extension, abduction, adduction and rotation involves co-ordination of various muscles. Extensor muscle relaxes when flexor muscle contracts and vice versa, flexor muscle relaxes when extensor muscle contracts. The coordination of opposing muscles is known as biomechanics. Occasional because of distraction or obstacles during activities the coordination falters and muscle injury occurs. Distraction or obstacles while running or playing contact sports may cause simultaneous vigorous contraction of flexor and extensor muscles during flexion of hip joint that may result tear of muscles of hip flexor.
- Muscle Fatigue Results In Hip Muscle Strain – Muscle gets fatigue after overuse or when not trained properly. Fatigue is the stage when muscle has reach metabolic endpoint. Metabolic endpoint suggest muscle glycogen concentration is depleted and blood glucose level is low. Inadequate energy supply to active muscles result in poor coordination and abnormal contractility. Continuation of sprinting or playing sports despite pain that is caused by muscle fatigue often follows hip muscle tear.
Causes of Hip Flexor Strain
Repeated flexion movements at hip joint causes frequent rigorous contraction or stretching of the hip flexors. Such action adds stress on muscles during and after activities. Excessive stress resulting from high force and too much repetition may force the hip flexor muscle fibers to tear resulting in hip flexor strain. The tear could be multiple microscopic or visible tear and most such injuries follows minor or intermediate bleeding and hematoma. The small and microscopic partial tear leads to minimal loss of function and minimal pain, while large tear to a total rupture may cause major disability and unexpected episode of severe pain.
Causes of Hip Flexor Strain:
- Muscle spasm
- Sudden explosive muscle contraction
- Repeated hip flexor muscle contraction
- Muscle tear
- Muscle weakness
- Joint stiffness
- Poor posture
- Poor core and pelvic instability
- Neural tightness
Muscle Spasm Results In Hip Muscle Strain-
Hip flexor strain is caused due to a sudden contraction of the hip flexor muscles, especially in stretched position. Such contraction causes spasm of hip flexor muscle fibers. The sudden flexion of untrained hip joint flexors frequently causes hip flexor stain.
Sudden Explosive Muscle Contraction Results In Hip Muscle Strain
Hip flexor strain is often caused while performing activities such as sprinting and kicking.2 The hip flexor strain results from a sudden explosive muscle contraction at the start of sprinting and kicking ball. Such muscle injury is seen during action of long kick in football game when kicker has not adequately warmed up. Similar injury is also observed in athletes who participate in long distance running and short distance sprinting.
Repeated Hip Flexor Muscle Contraction Results In Hip Muscle Strain
In some cases gradual development of hip flexor strain is observed when hip is repeatedly flex. Such prolong repetitive hip flexion causes strain on the hip flexor muscles. The stress induced on muscles by repeated contraction during repeated hip flexion results in hip flexor stain.
Muscle Tear Results In Hip Muscle Strain
Muscle tear is observed following injury caused by work accident, auto accident and domestic fall. The injured flexor muscle contract and goes into to muscle strain when flexor muscle is torn or adjacent muscle is injured.
Muscle Weakness Results In Hip Muscle Strain
Hip joint flexion involves several flexor muscles. If individual is suffering with weaknesses of some of these flexor muscles, then hip flexor that is normal ends up working harder. Repeated contraction then causes muscle strain and pain. Most muscle weaknesses are caused by long chronic illnesses, malnourishment, metabolic disorder and nerve injuries. Occasional individual suffering with malnourishment and prolong illnesses also suffers with muscle weaknesses.
Joint Stiffness Results in Hip Muscle Strain
Chronic illnesses resulting in prolong bed rest causes joint stiffness because of joint s not moved and become stiff. Similarly, aging and prolong non-activities causes joint stiffness. Individual during recovery starts moving his hip joint and feels sudden pain. The uncoordinated muscle contraction results in hip muscle strain secondary to muscle spasm or microscopic muscle tear. Such pain is in most cases results in flexor muscle strain.
Poor Core and Pelvic Instability Results in Hip Muscle Strain
Congenital skeletal abnormality like scoliosis, old fracture of pelvic as well as femur and old hip joint dislocation causes poor core and pelvic instability. Such injuries changes posture, causes premature muscle fatigue and loss of muscle coordination during activities. Individual suffering with poor core and pelvic instability may suffer with hip flexor strain.
Neural Tightness Poor Core and Pelvic Instability
Nerves branches out from spinal cord and passes through various tissue to peripheral targeting organ and tissue. Nerve fibers are tightly enclosed together and known as nerve bundle or spinal nerve. The spinal nerve causes pain and symptoms like tingling and numbness if pinched or irritated by surrounding tissue along its pathway. Pinch or irritation of nerve motor nerve causes uncoordinated contraction of hip flexor muscles. In several cases such uncoordinated muscle contraction causes muscle spasm or tear and results in flexor muscle strain.
Symptoms and Signs of Hip Flexor Strain
- Groin Pain
- Muscle Tenderness
- Hip Flexor Muscle Spasm
- Muscle Swelling
- Hip Joint Stiffness
- Groin Pain– Person with a strained hip flexor is li]kely to experience symptoms of pain on the front side of the hip. Sudden pain frequently become worse in very short time, may be in few hours. Pain intensity increases when leg is raised against resistance and this sign is considered diagnostic for hip flexor strain. Increased intensity of pain is also experienced on stretching these muscles. Pain is occasionally referred to other anatomical area. Sudden and sharp referred pain is felt in the hip or pelvis when hip flexor strain is caused by trauma.
- Muscle Tenderness- Muscle tenderness is a pain elicited when muscle is examined or palpated. Pain become worse when same muscle is squeezed. Thus, injured muscle or muscle inflammation causes muscle tenderness. Muscle tenderness is observed, when pain is felt in hip flexor muscle while examining hip flexor muscle. The tender hip muscle become tight and stiff following examination. Pain is felt in front of the hip joint or in the groin.
- Hip Flexor Muscle Spasm- Occasionally involuntary muscle spasm is observed when hip joint is flexed. Muscle spasm is caused by overuse of muscle that result in hip flexor muscle strain. Similarly, muscle spasm is also observed in normal hip flexor when adjacent muscle is injured. Hip flexor muscle spasm is felt like cramping, squeezing or clenching sensation in the groin, as well as upper leg area near groin. The hip flexor muscle spasm is also associated with loss of strength in flexor muscle that is spread over front of the groin. Loss of strength in muscles causes muscle weakness in hip flexor muscles.
- Bruising of Thigh and Groin- Hip flexor muscle tear causes bleeding. Slow bleeding often is not diagnosed during early stages and the blood oozes out in to subcutaneous tissue and skin become purple red. Such condition is known as bruises. The examination of bruises often causes severe pain in underlying muscle that is injured or torn.
- Muscle Swelling- Hip flexor muscle spasm when causes hip flexor muscle strain also causes firm swelling of muscle. The muscle swelling become painful and tender. Similarly, muscle also swells following injury because of muscle inflammation. Swelling in groin is also caused by hematoma (blood clot) in groin and upper thigh because of bleeding.
- Hip Joint Stiffness- Hip flexor strain causes continuous pain that restricts hip joint movement. After few days because of lack of movement of hip joint, the joint become stiff. Later pain intensity increases during any attempt to move hip joint that result in joint stiffness. Examination suggests individual suffering with flexor muscle stain is unable to move leg at hip joint.
Tests to Diagnose Hip Flexor Strain
Detailed subjective and objective examination that includes history and examination is performed to diagnose hip flexor strain or hip flexor tear. The initial diagnosis is confirmed with the positive findings of following investigations.
Radiological Examinations- Soft tissue injury like muscle tear may not be seen in X-Ray, Computerized tomography (CT scan) or Magnetic Resonance Imaging (MRI). X-Ray, CT Scan and MRI helps to rule out presence of fracture and dislocation of the hip joint. Muscle swelling, blood clots and bone abnormalities may be observed with MRI. Published paper suggests MRI images help to diagnose hip flexor muscle injuries and inflammation.3
Following choices of radiological investigations are used.
- CT scan.
- Ultrasound– Ultrasound can be helpful to evaluate blood clot and muscle injury.
- Blood Examination- White blood cell (WBC) count is increased if wound or one of the hip flexor muscle is infected.
Treatment for Hip Flexor Strain
Conservative Treatment for Hip Flexor Strain
Rest- Hip flexor strain is frequently caused by injuries. Injuries causes bleeding. Rest is advised during initial phase to reduce bleeding. Later on rest is needed for proper healing of injured muscles. In most cases 4 to 6 weeks of rest is advised. Rest is mostly restricted to injured hip. In most cases activities of knee and ankle joint is recommended.
Heat Therapy- Heat therapy for hip flexor strain is recommended only when wound and muscle injury is healed. Heat therapy helps to reduce pain. Heat therapy includes use of warm rubber bag and application of infra ray lights.
Cold Therapy- Cold therapy for hip flexor strain includes application of plastic or rubber bag that is filled with ice over the painful area and groin. In few cases frozen objects are also used. Cold or cryo therapy is useful during initial phase to control bleeding. The cold shrinks the blood vessels and causes vasoconstriction. Vasoconstriction or shrinkage of blood vessels causes less bleeding. Cold therapy is also used after recovery during rehab to decrease the pain.
Massage Therapy- Massage therapy for hip flexor strain is recommended once the muscle injury and inflammation is cured, and pain is tolerable. Massage therapy helps to rebuild tone and power of muscles. Initially deep massage is not tolerated thus, it is recommended to consider superficial massage and later deep massage is advised depending on pain tolerance. Massage therapy also helps to improve joint mobility.
Joint Stretching and Yoga Therapy- Once the wound is healed and pain intensity become tolerable, then joint stretching is recommended. Yoga therapy helps to stretch most of the joint that includes hip joint. Stretching is performed to improve hip flexion and extension.
Medication to Treat Hip Flexor Strain
Non-steroidal anti-inflammatory medication (NSAIDS)- NSAIDs helps to treat mild to moderate pain as well as tissue inflammation. In most cases muscle injury or spasm causes muscle inflammation. The treatment of 2 to 3 weeks helps for rapid recovery from hip flexor strain. NSAIDs most frequently prescribed are motrin, naproxen and celebrex.
Tylenol- Tylenol is used as an analgesics and not as anti-inflammatory medication. Tylenol 350 to 500 mg is prescribed 4 to 6 times a day for 2 weeks to treat hip flexor strain.
Opioids- Opioids are avoided to treat mild to moderate pain. Severe pain associated with hip flexor strain is treated with opioids like hydrocodone, oxycodone and morphine. Opioids causes dependence and addiction and can be life threatening when used for long period of time.
Antibiotics- Antibiotics are prescribed for infection. Infection is rare in condition like hip flexor strain. Occasionally infection is observed in patient who had sustained hip flexor strain following injury. Such infection is treated with antibiotics. Antibiotics are selected depending on bacterial or fungal cause of infection.
Physical Therapy- Sports and exercise must be avoided until injured flexor muscle is healed and injured leg muscle activities are pain free. Returning back to normal activities too quickly before appropriate recovery from Hip Flexor Strain or Hip Flexor Tear may result in chronic problem. Physical therapy for hip flexor strain is important in speeding up the healing process. Physical therapy also decreases the likelihood of recurrence of Hip Flexor Strain in future. The published scientific research data suggests 6 weeks training using elastic band had improved hip flexor muscle strength.4
Physical Therapy for Hip Flexor Strain or Hip Flexor Tear:
Ambulation- Ambulation training is necessary when suffering with pain caused by hip flexor sprain and also after recovery from sprain to improve ambulation without any assistance. Patient suffering with hip flexor strain is trained at physical therapy facilities during pain to move hip and lower back resulting that least pain. The training involves use of crutches and wheel chair.
Soft Tissue Massage- Is an effective treatment for hip flexor strain, but this has to be done during the recovery phase.
Application of Heat and Ice- Heat and ice is used for pain. In most cases heat and ice reduces intensity of pain and that allows to perform exercises to strengthen muscles.
Dry needling– Dry needing irritates muscle fibers and helps to divert pain. The dry needling helps to relieve mild to severe pain.
Activity Modification and Training- Patient suffering with hip flexor strain in most cases may take 4 to 6 weeks to recover from strain and become pain free. If pain continues then activity modification is necessary so individual can perform daily activities, while restricted painful hip joint. The experience physical therapist will supervise the training 2 to 4 times a week for 2 to 6 weeks depending on recovery time.
Electrotherapy- Electrotherapy involves passage of low energy electrical current to peripheral nerves that lies in subcutaneous tissue and muscles. Pain control helps to perform physical therapy, joint stretching and perform regular activities. Electrotherapy is used for pain as well as healing of strained muscles. Transcutaneous electrical nerve stimulation (TENS) is performed using TENS unit that creates current. The current is passed through a conduction pad that is left adhering to the skin that overlies painful area.
Ultrasound- Ultrasound therapy reduces pain. The ultrasound waves are high frequency waves that can penetrate skin and deeper soft tissue. Ultrasound waves reduces pain when the ultrasound strikes the sprain or injured muscles. The therapy is performed before beginning of the joint stretching and muscle exercises. The less painful muscles cooperate when joint stretching and muscle exercises are performed in physical therapy facilities.
Biomechanical Correction- After detailed examination, Rehab Physician and Physical Therapist will evaluate biomechanical abnormalities. Physical therapist then recommends correct posture during standing and sitting as well as use of normal muscles that is not hurting.
Surgery- Surgery for hip flexor strain is recommended if muscle is torn or dislocated from its attachment to bone.
Rehabilitation- Rehabilitation program1 is necessary for returning to sports activities and work. Rehabilitation program includes joint stretching exercises, muscle strength building, improve muscle coordination and use of equipment for ambulation. Rehabilitation program also includes modification of furnitures, door and desk at the place of work.
Hip Flexor Strain Recovery Period:
Strained hip flexor usually requires 2 to 3 weeks to heal if it is a minor tear. For a major tear of the hip flexor muscles to heal, it can take anywhere between 4 to 6 weeks or maybe a little longer in some cases of severe hip flexor strain.
Exercises for Hip Flexor Strain
Hip Flexion Exercise for Hip Flexor Strain:
Hip Flexion exercise for hip flexor strain is performed by lying down on the back. Now gradually bring the knee towards the chest as far as possible until a mild to moderate pain free stretch is felt and return back to the initial position. Perform 10 times ensuring there is no exacerbation of symptoms of hip flexor strain.
Hip Extension in Lying Exercise for Hip Flexor Strain:
Hip Extension exercise for hip flexor strain is performed by lying down on the back. Now by keeping the buttocks at the very edge of the bed or bench bring the healthy knee towards the chest as far as possible in order to drop the affected leg towards the floor. Hold the position for about for about two to five seconds until a mild to moderate pain free stretch is felt. Perform 10 times ensuring there is no exacerbation of symptoms.
Quadriceps Stretch Exercise for Hip Flexor Strain:
Quadriceps Stretch Exercise for hip flexor strain is performed by standing with the hands on a wall or counter for support. Grasp the top area of the ankle and foot on the affected leg. Now pull the foot in the upward direction in order to approach the buttock until a pain free stretch is felt on the front side of the thigh. Hold the position for about 30 seconds and release. Repeat three times.
REHABILITATION OF SOFT TISSUE INJURIES OF THE HIP AND PELVIS
Epidemiology of Hip Flexor and Hip Adductor Strains in National Collegiate Athletic Association Athletes, 2009/2010-2014/2015.
Characteristics of acute groin injuries in the hip flexor muscles – a detailed MRI study in athletes.
Large strengthening effect of a hip-flexor training programme: a randomized controlled trial.
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