Ligaments

PTP 521Musculoskeletal Disorders and

Dysfunctions

I. Ligaments

• Latin: Ligare: to tie or bindNamed:

1. Bones in which they insert2. Shape3. Relationship to joints4. Relationship to each other

Ligaments1. Connect two bones together

2. Stabilize joints

3. Connective tissue structure 4. Shared function of restraint 5. Proprioceptor for the joint

Histological Composition of Ligaments

• 2/3 water– Contributes to cellular function– Viscoelastic behavior

• 1/3 solid– Collagen (up to 27 types have been identified in ligaments,

generally considered to be one of 6 types– Proteoglycans – control collagen fibrillogenesis by

controlling fibril diameter and the rate of fibril formation– Elastin: <2% of most ligaments

Influence of Hormones on Ligaments

• Some ligaments have receptors for hormones (estrogen, progesterone, and androgens)

• Ligament function could be regulated by hormones

• Might be gender-specific of regulation

• Evidence to Support Hormonal Influence:– During pregnancy, hormone relaxin is released to

cause laxity in ligaments

– Women more likely to have benign joint hypermobility syndrome

– Ligamentous laxity during menstrual cycle – not clearly defined

Effects of Immobilization

• Load Deprivation: rapid deterioration in biochemical and mechanical properties

• Ligaments are strain-rate sensitive– Stronger and stiffer at higher loading rates

• Decrease in ligament mass causes net loss in ligament strength and stiffness

• Shift in ligament cell metabolism from a building or steady state to a destructive state

• Few weeks of immobility: ligament matrix quantity decreases

• Bone will resorb causing weakness at insertional sites

• Immobilization greater than 6-9 weeks can result in as much as a 50% reduction in strength

Effects of Exercise

• Response to exercise: increase strength and stiffness (minimally)

• Potential to increase ligament strength and stiffness no more than 10-20%

• Effects of exercise may be ligament specific

Ligament Injuries

• One of the most common injuries to joint

• MOI: Falls, twisting, getting hit

• Knee in particular is susceptible– 25-40%

Injury to Ligaments

1. Spraina. Definition: disruptions of

fibers of a ligamentb. Key point– Caused by a force that stretches fibers beyond

elastic limits

Mechanisms of Injury

• Joint Dependent

• Extrinsic Load applied to joint– Ligaments parts that are the best to restrain in

that position are loaded the most– Deform past elastic limit– Fail

• Force required and amount of instability occurring are dependent upon – 1) size of ligament

– 2) age of person

– 3) position of joint when force occurs

• Failure occurs at insertion, body of ligament or bone interface (avulsion)– Children– Adults

• Evaluate immediately after an injury

• Unstable only in the position of injury. – True of partial ligament tears only

• MRI, stress radiographs and arthrograms are all imaging studies to determine the existence of a ligament sprain

Avulsion Fractures

• Force: tensile loading of tissue

• Causes insertion site to pull away from bone taking a part of bone with it

Enthesitis

• Definition: inflammation of insertion of ligament or tendon

• Extra-articular

• Younger child may be called apophysitis

Ligament Sprains

• Classification of Sprains:

– Number of fibers disrupted

– Instability of the joint involved

Grade I: mild or first degree sprain

Signs: ROM limited in one direction only• Increase in pain during PROM and AROM –

when ligament is stressed• Limited bruising

Symptoms: localized tenderness over the injury area, pain

Grade II: moderate or second degree sprain

Signs: clinical evidence of instability

• Stress testing gives slight laxity but not complete functional instability

• Ecchymosis• Decrease in ROM,

painful, swelling restricts movement

• Edema

Symptoms: more diffusely tender

• Increase in pain• Instability with weight

bearing and with movement that would stress the ligament

• Generally parts of several ligaments are injured with a second degree

Grade III: severe or third degree sprain

Signs: significant laxity is seen, abnormal increase in ROM

• Severe swelling• Ecchymosis or

hemarthrosis• Structural, functional

instability

Symptoms: may be less painful than a grade II sprain

May also have second degree sprains in other ligaments

Joint Instability

Stress testing: compare the injured and the non-injured side

0 instability: No difference between injured and non-injured side

1+ instability: difference is less than 0.5 cm2+ instability: difference is between 0.5cm and 1cm3+ instability: difference is greater than 1cm

Ligamentous Healing

Phase 1: Inflammation, occurs within 72 hours. – Inflammatory response– Immediate pain and bleeding– Extra-articular ligaments: bleeding outside joint

cavity– Intra-articular ligaments: bleeding within joint

cavity

Phase 2:

Repair/Regeneration: 48-72 hours after injury and lasts up to 6 weeks– Production of scar matrix, viscous material

becomes less viscous as days go on

Healing Failure:

a. failure to reconnect appropriate locations on bones

b. failure to produce enough scar tissue c. failure to produce the correct type of tissue

Phase 3:

Remodeling: 6 weeks to 12 or more months to complete – Over time, becomes more ligamentous, some

differences exist in both composition and architecture of the ligament.

Surgical Repair Guidelines

1. Patient is high risk for instability in the future

2. Age of patient

3. Type of ligament sprain that occurs

4. Associated lesions, degree of laxity

Types of Surgeries

• Repair: reattachment of torn ends of a ligament

• Reconstruction: replacement of original ligament with a graft– Autograph– Allograph