Sprains and StrainsThe Biomechanics of Injury

Janus D. Butcher

UMD School of Medicine

June 2007

Sprains and Strains

• Biomechanical Model

• History and Physical

• Initial Treatment

• Rehabilitative Treatment

• Illustrative Cases/Complications

Definitions

• A sprain is?

Definitions

• A sprain is?

Ligament Injury

Definitions

• A strain is?

Definitions

• A strain is?

Musculotendinous Injury

Biomechanical Model of Acute Ligament/tendon Injury

• Acute injury occurs when a ligament or tendon is subjected to tensile stress (load) that exceeds it’s tensile strength.

Biomechanical Model of Overuse Injury to Ligament or Tendon

• Overuse injury occurs when ligament or tendon is subjected to repetitive tensile stress at a frequency, duration, and intensity that exceed its capacity for recovery or repair.

Concentric Contraction/Load

• Muscle shortens as it exerts force.

Eccentric Contraction/Load

• Muscles are forced to lengthen while exerting a force

Biomechanical ModelFactors That Increase Risk of Injury

• Increased tensile stress

• Decreased tensile strength

• Decrease capacity for repair

Increased Tensile Stress

• Eccentric overload

• Ballistic velocity

• Weak supporting dynamic stabilizers

• Proprioceptive deficit

• Proprioception is…..

Balance

Decreased Tensile Strength

• Prior injury• Disuse atrophy• Degenerative disease• Aging• Connective tissue

disease• Medications

Decreased Capacity for Repair

• Recurrent injury

• Aging

• Connective tissue disease

• Vascular disease

• Diabetes

• Smoking

• Medications

• Other

Biomechanical ModelInjury Prevention

• Decrease tensile load (stress)

• Increase tensile strength

• Enhance ability for repair

Decrease Tensile LoadExtrinsic Factors

• Proper equipment• Proper technique• Bracing/taping• Orthotics

Increase Tensile StrengthIntrinsic Factors

• Resistance exercise (eccentric loading)

• Balanced strengthening of dynamic stabilizers

• General conditioning

• Proprioception training

Enhance Capacity for Repair

• Conditioning

• Lifestyle

• Drugs

Sprains and StrainsMechanism of Injury

• Deformation injury produced by stress

• Musculotendinous injuries usually eccentric overload

• Ligament injuries usually non-anatomic stress

Musculotendinous Injury

• Eccentric overload

                                      

                 

Ligamentous Injury

• Non-Anatomic Stress

Grading Severity

• Grade 1: Micro-tears (stretch)

• Grade 2: Macrotears (partial tear)

• Grade 3: Complete disruption

Joint Laxityvs.

Joint Instability

Joint Stability

• Musculotendinous unit and ligaments are symbiotic in joint stability

• Static stabilizer vs. dynamic stabilizers

Functional Instability

• Not the same as joint laxity

• Frequently describes “giving out”

• Unable to do certain activities• Jump

• Pivot

• Decelerate

• Cut

Functional InstabilityPossible Causes

• Ligamentous laxity

• Motion deficit

• Strength or endurance deficit

• Proprioception issues

• Internal derangement (fracture/loose body)

Sprains and StrainsPhysical Exam

• Inspection• Swelling

• Bruising

• Pain Provocation • Motion

• Palpation

Physical ExamPalpation

• Crepitance

• Weakness

• Palpable defect

Physical ExamStress Testing

• Laxity

• End Point

Modifiers of Endpoint

• Muscle tone• Muscle guarding• Joint effusion• Soft tissue swelling• Mechanical block• Ligamentous endpoint

Physical ExamCaveats

1. The patient will tell you what’s wrong

2. The exam may or may not be confirmatory

Initial Treatment

• P Protection• R active Rest• I intermittent Ice• C Compression• E Elevation• M anti-inflammatory Medication• M anti-inflammatory Modalities

Rest

Rest

• A four letter word

Rest

• A four letter word

• Relative rest implies ACTIVE rest

Active RestTreatment Implications

• Stimulates healing of tissue

• Allows maintenance of general conditioning

• Prevents loss of strength in supporting structures

• Maintains joint ROM

• Addresses proprioception retraining

Active Rest

• Activity is performed in a biomechanically normal position

• Protected from abnormal motion

• No pain with activity

• No pain or swelling after activity

Rehabilitative Exercise

• Goals• Control immediate inflammatory response

• Promote normal tissue healing

• Increase tensile strength

• Address collateral joint effectors

• Maximize functional stability

Who Gets Therapy?

Everyone!

Return to Sport

• Absence of pain is not appropriate end-point of treatment -Webb

• Strength >80% on normal

• ROM normal

• Proprioception normal

Return to SportBracing

• Almost everyone

• Functions• Support Joint

• Enhance proprioception

• Ensure• Appropriate fit

• Use with specified activities

Case

• 24 year old student hockey athlete slid feet first into the boards.

• He saw it coming and tried to stop his crash.

• Felt a ripping sensation in his left thigh and was unable to bear weight.

Physical Exam

Physical Exam

• Swelling

• Bruising

• Palpable defect in the vastus lateralis

• Negative extensor lag

Imaging

• Xray- none initially

• MRI

Treatment

• P Knee immobilizer• R Knee immobilizer/flexion block

splint• I Ice• C Ace Wrap• E Elevation• M No• M NSAIDS (Indocin)

Therapy

1. Initial rest until able to weight bear

2. Gentle stretching

3. Gradual eccentric exercise (2-4 weeks)

4. Dynamic flexibility and strengthening

5. Return to sport 4 to 8 weeks

Complications

• Re-injury

• Complete tear

• MO

Prevention of Myositis Ossificans

• Avoid repeat injury

• Avoid aggressive activity early

• Indocin 50mg t.i.d.

Case

• 33 year old runner sprained ankle 1 year ago.

• Was very bruised and swollen but symptoms subsided without treatment

• Now has had multiple ankle sprains over the past year and ankle feels very unstable.

Physical exam

• Inspection: Normal• Tender in the anterio-

lateral corner• Weakness in peroneus

brevis• ROM: diminished

dorsiflexion

Physical exam

• Anterior drawer/talar tilt are normal

• Proprioception: Poor balance on injured side

Diagnosis?

1. Ankle sprain (recurrent grade 2 or less)

2. Synovitis

3. Functional instability

Treatment

• Brace

• Strengthing

• ROM

• Proprioception

Questions?