O&T SC058: Painful Knee After Football: Sport Injury

Question 1

History taking in Knee

Answer 1

Same as Shoulder (see SC057)

1. Pain
   - Presence of pain in involved region in acute injury is usually NOT helpful in arriving the diagnosis
   —> ***Absence of pain is MUCH MORE helpful (indicate not that significant unless there is sensory deficit (but uncommon))
2. **History of Trauma
   - **Mechanism of injury (High / Low energy)
   - ***Injury is significant?
   —> Definite traumatic in High energy trauma in normal tissue
   —> Degenerative / Overuse in Low energy trauma in “weakened” tissue
3. ***Swelling
   - No swelling
   - Mild delayed swelling (1-2 days later)
   - Immediate swelling
4. Giving way
   - Quadriceps weakness / Secondary to pain (Pseudoparalysis)
5. Walking ability
   - including use of walking aid and walking distance

Question 2

Significant injury vs Trivial injury

Answer 2

Significant:
- Injured tissue is normal before injury —> **Potential to heal —> Can do **early surgery to facilitate healing
- Tissue damage because force > ultimate failure strength of tissue
- e.g. traumatic meniscal tear, fracture patella
—> ***Definite traumatic problem
—> Young patients: High energy trauma
—> Elderly patients: Low energy trauma

Trivial:
- Injured tissue is weakened by pre-existing pathology
- Tissue is damaged even under physiological loading
- e.g. degenerative meniscal tear, collapse in SPONK (spontaneous osteonecrosis of the knee)
—> **Degenerative (Elderly) / **Overuse (Young) instead of Traumatic
—> Probability of healing is **low though symptoms may improve with **non-operative treatment

No injury:
- Exacerbation of symptoms of a pre-existing pathology
- No new / recent damage
- e.g. pre-existing meniscal tear, OA
—> **Degenerative (Elderly) / **Overuse (Young) instead of Traumatic
—> Probability of healing is **low though symptoms may improve with **non-operative treatment

Question 3

Swelling of knee joint

Answer 3

Fluid:
1. Synovial fluid
- Exudate / Transudate

2. Blood
   - Haemarthrosis (Immediate swelling)
   —> 72% have **ACL deficiency (∵ torn of blood vessels supplying it)
   —> 14% **Osteochondral fracture (bone + cartilage component)
   —> 6% ***Patellar dislocation (∵ rupture of the medial restraints of the patella)
3. Pus
   - ***Septic arthritis

Timing:
1. No swelling
- Chance of suffering from significant knee injury is low
- Worthwhile to observe

2. Mild delayed swelling (1-2 days later)
   - **Reactive effusion (synovial fluid) secondary to injury of **extra-articular structure (e.g. isolated MCL sprain) / **intra-articular structure which is relatively avascular (e.g. **meniscus injury, cartilage damage)
3. Immediate swelling
   - Acute haemarthrosis
   —> **ACL deficiency
   —> **Osteochondral fracture
   —> ***Patellar dislocation

Question 4

Painful knee after football

Answer 4

1. ***Ligament Injury
   - ACL, PCL
   - MCL, LCL
   - Knee dislocation
2. ***Meniscal Injury
3. ***Patella Dislocation
4. Cartilage injury
5. Extensor mechanism injury
6. Hamstring Tendon injury
7. Long bone fracture
8. Muscle injury
9. Capsule injury

Presentation:
1. On site
2. 1-2 days later injury
3. A few months later (mild initial presentation)

Question 5

Natural history of Knee disease

Answer 5

Always heal:
1. **MPFL (Medial patella-femoral ligament) tear in **Patellar dislocation
- High recurrent dislocation rate if patella is subluxed ∵ MPFL heal in elongated manner, lost its function of restraining lateral displacement

2. ***MCL tear (Grade 1 / 2)
   - usually Extra-articular structure ∵ can form a containing haematoma —> can initiate inflammation + healing

Treatment:
- ***Non-operative —> if fail then Surgery

Sometimes heal:
1. ***Meniscus tear
- esp. those close to menisci-capsular junction, although blood supply not as good as extra-articular structures

2. ***MCL tear (Grade 3)
   - may result in persistent laxity resulting in knee instability

Treatment:
- ***Surgical repair (Need of early surgery to allow better healing + preserve function)

Seldom heal:
1. ***ACL mid-substance tear
2. Cartilage (Chondral) tear (lesion replaced by fibrocartilage (scarring) with early OA)

Treatment:
- Reconstruction / Regeneration at ***elective setting (No need to rush)

(Regeneration: Autologous chondrocyte implantation operation)

Question 6

Knee anatomy

Answer 6

Intra-capsular ligament:
- ACL, PCL

Extra-capsular ligament:
- MCL, LCL
- Patellar ligament

ROM:
- Flexion, Extension

Question 7

***P/E of Knee

Answer 7

• Supine / Sitting
• Normal side before abnormal

Inspection:
1. **Deformity
- possible displaced long bone fracture / dislocation (e.g. lateral patellar dislocation)
2. **Wound and bruises
- possible injury to extra-articular structure —> bleed into SC tissue (e.g. bruise along medial aspect of knee joint may indicate MCL tear)
3. Muscle wasting
4. Sign of inflammation, Scar

Palpation:
1. **Joint line tenderness
- indicate site of tissue damage (e.g. tenderness at medial femoral epicondyle indicate injury origin of MCL)
2. **Effusion
- obliteration of **para-patellar gutter
- swelling of **supra-patellar pouch (most spacious cavity in knee)
- **positive fluctuation sign
- **positive patellar tap test (patellar bouncing up after pressing down, need >=50ml fluid)
- immediate swelling: Haemarthrosis

ROM:
1. **Active
2. **Passive
- Active before Passive ROM
- 4 readings:
—> **Passive + **Active extension (more important in acute injury)
—> Passive + Active flexion

Muscle power:
1. ***Quadriceps

Special tests:
1. ***Collateral ligament
2. Cruciate ligament (Lachman, Anterior drawer, Pivot shift test)
3. Meniscus (McMurray test)
4. Patello-femoral joint stability

***: Important in acute injury setting, others not as important

(NB:
- P/E is sensitive for Ligament, Muscle but NOT sensitive for Meniscus, Cartilage, Tendon —> require imaging
- NOT all P/E are helpful in acute haemarthrosis and severely painful knee)

Question 8

P/E: ROM of Knee

Answer 8

• Supine / Sitting
• Normal side before abnormal
• Active before Passive ROM
• 4 readings:
  —> **Passive + **Active extension (more important in acute injury)
  —> Passive + Active flexion

Flexion deformity / contracture:
- Decrease passive extension (lack of full extension)
1. Pain
2. Mechanical block inside knee (Locking) (e.g. displaced meniscus tear)

Extension lag:
- Discrepancy between active and passive extension of knee (large discrepancy is never due to pain / weakness!!!)
1. Quadriceps weakness
2. Loss of integrity of extensor mechanism (e.g. fracture patella, rupture quadriceps tendon —> ***emergency)

***Locking:
- Semi-emergency
- Not heal on its own —> meniscus function will be lost —> premature OA

Question 9

P/E: Collateral ligament: MCL

Answer 9

***Valgus stress test
- Supine / Sitting

Examiner:
- Holds the proximal tibia with both hands and puts the ankle within his axilla
- Beginning: Knee in **full extension
- Sustained **valgus stress
- Repeats the test with knee in ***30o flexion (usually some degree of opening up)

Finding:
- Feels for ***opening up of the joint

Precaution:
- Avoids ipsilateral hip movement

Grade 1 (Sprain):
- 0-5 mm opening up when compared with normal side
- Pain on valgus stress
- MCL macroscopically intact but microscopically tear —> good prognosis, good healing

Grade 2 (Partial tear):
- 6-10 mm opening when compared with normal side
- ***Firm end point
- Macroscopically tear but partial thickness tear / full thickness tear with partial width —> good prognosis, good healing with some laxity

Grade 3 (Complete tear):
- >10 mm opening when compared with normal side
- No end point
- Full thickness + full width tear —> poor prognosis, heal in a elongated manner with scarring in between, incompatible with normal —> early surgery to restore integrity + minimise laxity

Question 10

P/E: Meniscus

Answer 10

***McMurray test

Examiner:
- Compression force (Axial load) to the knee
- Grind the meniscus by **rotation (Varus + **Valgus force to grind medial + lateral meniscus)
- ***Extension of knee: grind posterior to anterior meniscus

Finding:
- Pain
- Sensation of click/clunk (indicate displaceable meniscus)

Precaution:
- Watch the patient’s face to avoid excessive pain during the test

No need to perform McMurray test in acutely injured knee with significant pain
- ***Always positive in significant acute injury —> perform after a few weeks

Question 11

ACL

Answer 11

• Intra-articular
• Originate on medial wall of ***lateral femoral condyle
• Runs downward, **forward and **medially
• Inserts into the anterior aspect along the midline of tibial articular surface

Functions:
Primary restraint
1. Resist excessive ***anterior translation of tibia relative to femur
—> Lachman test
—> Anterior drawer test

2. Resist excessive ***internal rotation of tibia relative to femur
   —> Pivot shift test

Secondary restraint
3. Resist excessive ***valgus movement of knee

Question 12

ACL deficiency

Answer 12

Mechanism of injury:
Low energy injuries during athletic activities
- Direct contact injury resulting in **hyperextension / **valgus stress on the knee
- Indirect non-contact mechanism e.g. **sudden deceleration / **rotation maneuvers

History:
- ***“Popping” / tearing sensation at the time of injury
- Immediate or early swelling of knee within 12 hours from injury
- Cannot continue the game
- +/- difficulty in bearing weight and instability of knee in terms of giving way

P/E:
1. **Gross knee swelling (∵ **Haemarthrosis)
2. ROM
3. ***ACL insufficiency sign
- Lachman
- Anterior drawer
- Pivot shift
4. Status of Collateral ligament
- ∵ commonly associated with concomitant MCL injury and meniscal injury

Purpose of P/E:
Rule out co-existing condition requiring **early surgery:
- **Avulsion fracture of cruciate ligament
- **Displaced meniscus tear (esp. bucket handle) with acute locking
- **Grade 3 Collateral ligament injury

Investigations:
1. X-ray
- make sure ACL deficiency is from mid-substance (ACL its own) but not from bone (i.e. avulsion fracture)
2. MRI
- not a must
- find out cartilage injury / meniscal tear which not cause locking (i.e. cannot be detected on P/E)

Diagnosis:
1. Acute haemarthrosis after knee injury proven by arthrocentesis (∵ 70% have ACL injury)
- very helpful

2. Symptoms of instability (esp. on pivoting sport)
   - only know after some time after initial injury
3. Signs of ACL deficiency on P/E
   - Lachman test
   - Anterior drawer test
   - Pivot shift test
   - ACL deficiency signs are difficult to be elicited at the time of acute injury ∵ involved knee is too painful (“Guarding”)
4. Radiographic evidence of ACL
   - Deficiency on MRI

Question 13

P/E: ACL: Lachman test

Answer 13

Beginning:
- Knee in 20-30 degree of flexion

Examiner:
- Stabilise the femur with one hand
- Anterior pulling force on the tibia with the other hand

Finding:
- ***Excessive anterior translation of proximal tibia

Question 14

P/E: ACL: Anterior drawer test

Answer 14

Beginning:
- Knee in 90 degree of flexion

Examiner:
- Stabilise the distal tibia by sitting on the foot
- ***Check the relaxation of the hamstring
- Anterior drawer force on the tibia with both hands

Finding:
- ***Excessive anterior translation of proximal tibia when compared with the normal side

(From SpC O/T: Always do posterior sagging first to exclude PCL deficiency before doing Anterior drawer’s test, otherwise you can always pull knee forward if knee already sagged)

Question 15

P/E: ACL: Pivot shift test

Answer 15

Beginning:
- Knee in **extension + **internal rotation
- Patient relaxed

Examiner:
- **Valgus stress to proximal tibia
- **Flex the knee from full extension to 30-40 degree flexion

Finding:
- Observe for ***clunk or “jump” of proximal tibia (Reduction of subluxed (anteriorly + internally rotated) tibia back to original position)

No need to perform Pivot shift in acutely injured knee with significant pain
- **always negative in pain
- too painful to be performed: **“Guarding”

Question 16

Investigations

Answer 16

1. X-ray
   - 3 views: AP, Lateral, ***Tangential view of PFJ (Skyline view) (+/- Tunnel view)
   - 2 sides (abnormal + normal side esp. in immature skeleton for comparison)
   - +/- Special view
   - +/- 2 Joints
   - +/- 2 Occasions

(NB:
- Most dislocation may have normal X-ray ∵ spontaneous reduction
—> rely on P/E
—> if Grade 3 laxity (**Complete tear) in **3 out of 4 major knee ligaments
—> Dislocation until proven otherwise
- X-ray can be subtle)

2. CT
3. USG
4. MRI
   - Able to visualise ***cartilage as well

Question 17

Choice of Management of significant knee injury

Answer 17

2 questions to answer:
1. Whether damaged tissue can ***heal by itself?
Prerequisites:
- Injury in normal tissue
- Acute injury
- Reasonable vascular supply
- Minimally displaced

2. Whether after healing is ***compatible with normal function / not result in persistent symptoms?

Yes to both —> Observation / Non-operative treatment

No to either —> Surgery
- Urgent / Early / Elective
- Repair / Resection / Reconstruction / Replacement / Regeneration (Depend on nature of pathology)

Question 18

***Need for early surgery

Answer 18

1. Subluxed patella after patellar dislocation
2. ***Displaced meniscus tear (esp. bucket handle) with acute locking
3. Rupture extensor mechanism (Fracture patellar / Rupture of Quadriceps tendon)
4. Osteochondral fracture
5. ***Avulsion fracture of cruciate ligament
6. ***Grade 3 Collateral ligament injury

Question 19

***Management of knee injury

Answer 19

• Rule out need of ***Early surgery
• Re-examine patient in OPD clinic ***2-3 weeks later to make diagnosis + check ACL status

P/E:
1. Deformity
- Dislocation / Fracture +/- **Neurovascular injury
2. Wound
- Abrasion vs Open fracture
3. **Neurovascular status (may be compressed, must examine)

First aid treatment:
1. +/- Reduction (not aim at total correction but better alignment)
2. +/- Wound cleaning
3. ***RICE (+/- Immobilisation)

Definitive conservative management:
1. **Analgesics
2. **Physiotherapy
- Quadriceps strengthening exercise
- Knee mobilisation exercise
- Ankle pump exercise
3. ***Walking exercise with crutches
4. +/- Protection by bracing / POP

Definitive surgery:
1. ***ACL reconstruction (Delayed surgery (Early surgery may lead to too much scarring i.e. arthrofibrosis)) if indicated

Further investigation:
1. X-ray
2. Knee aspiration
- confirm haemarthrosis
- diagnostic (fat globules indicate potential fracture) + therapeutic (relieve pain + improve motion)
- CI: heavy contamination of region, infection of adjacent structure

Question 20

***Management of ACL deficiency

Answer 20

1. Rule out co-existing condition requiring **early surgery
   - **Avulsion fracture of cruciate ligament
   - **Displaced meniscus tear (esp. bucket handle) with acute locking
   - **Grade 3 Collateral ligament injury
2. Conservative management
   - **RICE
   - **Analgesic
   - **Early return of full ROM —> preservation of Quadriceps
   - Allow FWB walking with crutches if isolated ACL mid substance injury
   - Allow patient to be discharged 1-2 days later
   - **Re-examine patient in OPD clinic 2-3 weeks later to make diagnosis + check ACL status
   (Only conservative treatment will increase chance of repeated knee injury and resultant meniscal / chondral damage + premature degeneration of knee joint)

Mid substance injury to ACL:
- ***Poor healing potential due to its intra-articular location and thin synovial envelop
- ACL Reconstruction

Avulsion fracture of ACL:
- ***Good healing potential if correct reduction
- Internal fixation

3. Make diagnosis of ACL mid-substance tear
   - P/E signs will be obvious to make diagnosis
4. **ACL Reconstruction
   - Repair **NOT an option (∵ do not heal on its own)
   - **Tendon graft to replace ACL
   —> Autograft / Allograft
   —> Bone-Patellar Tendon-Bone Graft vs Medial Hamstring Graft
   - Perform in **elective setting when acute phase of inflammation subside (∵ complication of arthrofibrosis in too early surgery)

Indications for surgery:
- Want to return to pivoting sport
- Persistent symptoms of instability despite giving up pivoting sport (e.g. obese patient, concomitant injury of other ligaments)
- Minimise chance of repeated intra-articular injury and hence subsequent premature OA knee
—> only 1/3 of patients report deteriorating symptoms and require surgical stabilisation

Question 21

Knee dislocation

Answer 21

Consider potential knee dislocation if:
1. Complete rupture of three major ligaments
2. Complete rupture of both ACL + PCL

• X-ray may appear normal because of spontaneous reduction
• Chance of persistent instability and potential neurovascular injury

Question 22

***Management of Knee dislocation

Answer 22

Initial assessment
1. Assess ***neurovascular status
- if distal circulation confirmed to be intact initially
—> regular monitoring of vascular status should be carried out every 2-3 hours within 1st day
- if doubt about vascular status —> Doppler USG / Angiogram should be performed in an urgent basis

Initial management
2. Knee should be reduced ***urgently + immobilised (to minimise seoncadry damage)
- Long leg backslab with knee in reduced position (usually adequate)
- External Fixator:
—> Open dislocation
—> History of vascular repair
—> Joint reduction that cannot be maintained adequately in a splint

3. Vascular injury —> Urgent exploration + Repair +/- Vascular reconstruction
4. Nerve injury (e.g. common peroneal nerve) —> Exploration + Repair can be carried out at the time of Vascular repair (Can also wait if no vascular repair —> majority is neurapraxia —> can heal in 3-6 weeks)

Definitive treatment
1. Rule out need of early surgery
2. Definite management of ligament injury in elective setting
- 1st stage Repair of grade 3 collateral ligament injury
- 2nd stage Reconstruction of cruciate ligament

Question 23

Summary of lecture

Answer 23

• Clinical approach of painful knee after acute soccer injury
• Principle of management of musculoskeletal injury
• “Rule out need of early surgery”
• Principle of management of ACL-related acute haemarthrosis
• Principle of management of knee dislocation

Question 24

Medial knee structures

Answer 24

Provides stability against valgus + external rotation
1. MCL (Superficial / Deep)
- Tensed up on knee flexion and relaxed on extension
2. Posterior oblique ligament
- Tensed up on extension and relaxed on flexion

History:
- Direct blow to the lateral aspect of leg or lower thigh
- Non-contact injury from cutting, pivoting or twisting
- Present with medial knee pain +/- reactive swelling

P/E:
- Possible bruise at the site of injury
- Localised tenderness along the course of MCL
—> Femoral origin
—> Mid substance
—> Tibial insertion
- ***Valgus stress test

Grade 1 (Sprain):
- 0-5 mm opening up when compared with normal side
- Pain on valgus stress
- MCL macroscopically intact but microscopically tear —> good prognosis, good healing

Grade 2 (Partial tear):
- 6-10 mm opening when compared with normal side
- ***Firm end point
- Macroscopically tear but partial thickness tear / full thickness tear with partial width —> good prognosis, good healing with some laxity

Grade 3 (Complete tear):
- >10 mm opening when compared with normal side
- No end point
- Full thickness + full width tear —> poor prognosis, heal in a elongated manner with scarring in between, incompatible with normal —> early surgery to restore integrity + minimise laxity

Treatment:
Isolated Grade 1 and 2 Injury
1. Conservative Treatment
- Good potential to heal though usually with residual medial laxity

Grade 3 injury
- Complete rupture of MCL
1. Surgery
- Controversial
- Commonly associated with other ligament injuries which compromise knee stability

Question 25

PCL

Answer 25

• Intra-articular
• Originates on the ***lateral wall of the medial femoral condyle
• Runs downward and ***posteriorly
• Inserts into posterior aspect tibial articular surface at about 1-1.5 cm below the joint line

Functions:
Primary restraint
1. Resist excessive posterior translation of tibia relative to femur

Secondary restraint
2. Resist excessive external rotation of tibia relative to femur (more significant at 90 degrees knee flexion)

Question 26

PCL deficiency

Answer 26

Mechanism of injury:
- Usually result of direct **high energy trauma —> RTA
—> Dashboard injury with direct posterior hit on anterior aspect of proximal tibia with the knee in flexed position
- Can occur in **contact sport activities, such as football, baseball, skiing and soccer with fall on a **flexed knee with foot in **plantar-flexed position
- Non-contact injury (forced hyperflexion of knee and knee hyperextension) is less common

History:
- **Rarely report “popping” sensation at the time of injury
- Usually will **not experience a sense of instability
- Mild to moderate swelling of knee
- May experience stiffness of knee and report mild posterior knee pain

P/E:
1. Knee swelling
2. Possible “Tale-telling” **bruise in anterior aspect of proximal tibia
3. Presence of PCL insufficiency sign
- **Posterior sagging of tibia
- Loss / Reduction of normal medial step off (Tibia should be anterior to Femur)
- ***Posterior drawer test
4. Commonly associated with concomitant PLC (Posterior-lateral complex) injury

Question 27

Management of PCL deficiency

Answer 27

Low grade isolated midsubstance PCL injury:
- Conservative Treatment

High grade symptomatic isolated mid substance PCL injury:
- PCL reconstruction

Combined PCL and PLC injury:
- Combined PCL and PLC reconstruction

PCL avulsion fracture:
- Undisplaced: Conservative treatment
- Displaced: ORIF

Question 28

LCL

Answer 28

• Femoral side: insertion is just posterior and proximal to lateral epicondyle
• Fibular side: 8 mm from anterior border of fibular head

Functions:
1. Primary static **varus restraint for the knee (esp. at 30 degrees flexion)
2. Limit **external rotation at 30 degrees of flexion

Question 29

LCL deficiency

Answer 29

Mechanism of injury:
- Sports injuries / high energy trauma
- Direct blow to the **anterior-medial tibia with the knee in **extension (most common)
—> forceful **hyperextension with **external rotation and ***varus
- Contact or Noncontact hyperextension
- Varus non-contact force

History:
- Pain along the posterior-lateral aspect of knee
- Swelling often minimal
- Varus thrust gait with feeling of instability with the knee approaching full extension
- May be associated with symptoms of common peroneal nerve injury

P/E:
- ***Varus stress test

Question 30

Management of LCL deficiency

Answer 30

1. Conservative mostly
2. Surgery
   - Avulsion fractures
   - Multi-ligament injuries
   - Grade 3 injuries

Question 31

Meniscus

Answer 31

• 2 pieces of fibrocartilage inside knee joint
• situated between femoral condyle and tibial plateau
• semi-lunar shape when viewed from above
• triangular shape in its cross section
• anchored to tibia in anterior + posterior horn by root of meniscus —> prevent extrusion of meniscus + create Hoop stress to maintain shape and distribute load

Medial meniscus:
- ***Semi-circular
- Bound to the joint capsule peripherally
- Deep part MCL
- Bears 50% load across medial compartment

Lateral meniscus:
- ***Circular
- Bound to the joint capsule peripherally
- Popliteus tendon
- Anterior and posterior meniscofemoral ligament (Humphrey and Wrisberg)
- Bears 70% load across lateral compartment

Tensile stiffness:
- Circumferential (110 MPa)
- Radial (10 MPa)

Compressive stiffness:
- 0.1% of Circumferential tensile stiffness

Low potential of healing:
- Medial, Lateral, Middle genicular arteries through perimeniscal capillary plexus
- only peripheral 3-4mm is vascular —> capable of healing
- central meniscus is avascular —> low healing potential
- hostile biomechanical environment

Functions:
1. **Load transmission
- maximise contact surface area (meniscus包住distal femur) —> reduce contact pressure —> **Chondral protection
- resist compressive force but under tremendous shear load
- 50% forces in extension, 85% in flexion
2. **Shock absorption
- viscoelastic deformation
3. **Lubrication and nutrition
4. Secondary ***stabilisation (+ proprioception)

Contents:
1. Cells
- fibrochondrocytes, fibroblasts (produce type 1 collagen + maintain extra-cellular matrix)
- cells of superficial zone
2. Extra-cellular matrix
- water (70%)
- ***GAG (1%) (chondroitin, dermatan, keratan sulphate)
—> negatively charged —> allow water to bind —> low compressive stiffness —> expand under compressive force —> increase surface area —> decrease contact pressure —> suitable for shock absorption + resist compressive force
- collagen (20%) (type 1 collagen 90%)
—> peripheral 1/3: circumferential arrangement (90%) —> high circumferential stiffness
—> inner 1/3: radial arrangement (10%) —> prevent splitting

Question 32

Meniscal injury

Answer 32

1. Prone to injury
   - Esp. ***twisting injury
   - Can occur alone or associated with other ligamentous injury (esp. ACL)
2. Difficulty in Healing
   - Relative **avascular structure (except the peripheral rim)
   - Hostile mechanical environment because of physiological **loading

Symptoms:
- Mechanical pain
- Swelling
- ***Locking (most helpful symptom, indicate displaceable meniscus tear)
- Giving way

Signs (not specific / sensitive):
- Effusion
- Joint line Tenderness
- Reduced ROM (Active + Passive)
- Provocative signs (**McMurray Test, **Apley grinding test)
- Quadriceps wasting
- ***Palpable clunk (in case of discoid meniscus)

Investigations:
- X-ray
—> often unremarkable
—> important in ruling out other DDx

Diagnosis:
1. MRI
2. Diagnostic arthroscopy

Question 33

Classification of Meniscus tear

Answer 33

Significance in Diagnosis + Management

1. ***Traumatic / Degenerative (ONLY need to know this classification, Predict potential to heal)
2. Acute / Chronic (repair often not possible)
3. Partial (no need repair) / Full thickness
4. Morphology (Longitudinal (repairable) / Horizontal / Radial / Complex)
5. Location (Anterior horn / Posterior horn / Body / Root)
6. Vascularity (“Red-red” / “Red-white” / “White-white”) —> Predict potential to heal

Question 34

Traumatic meniscal tear

Answer 34

***Repair ASAP to preserve meniscus

• Meniscus ***healthy before onset of symptoms
• ***Potential of healing if repaired promptly
• Always associated with history of ***significant injury
• Onset of first symptom is always acute
  —> Symptom: Instability of torn meniscus (Pain + ***Locking)
  —> Sign: Joint line tenderness, Effusion, Positive McMurray test / Apley grinding test

Acute setting:
- “**Acute locking” (loss of terminal passive extension ∵ persistently displaced meniscus fragment blocking extension)
- **Joint effusion
- Provocative test ***limited role ∵ non-specific + always positive in acutely injured knee (even in absence of meniscus tear)

Subacute setting:
- “Intermittent locking” (displaceable meniscus tear, symptom occur when displaced and disappear when fragment is reduced to original position)
- Joint line tenderness
- Effusion
- ***Positive McMurray test / Apley grinding test (always present, but non-specific)

Question 35

Degenerative meniscal tear

Answer 35

***NOT attempt repair —> Observe / Meniscectomy

• Tear occur in meniscus with ***pre-existing pathology (e.g. degeneration, untreated chronic traumatic tear, developmental problem (e.g. discoid meniscus))
• ***NO / LOW potential of healing even if repair is attempted
• Symptom may happen
  —> Even if no injury (∵ weak initially) / After insignificant injury / Significant injury
  —> History of injury is not important
• Onset: Acute / Insidious

Chronic problem —> mainly symptom with displaceable meniscus fragment:
- Pain
- ***Intermittent locking
(Joint line tenderness, Effusion, Reduced ROM, Provocative test may / may not present)

Primary degenerative:
- 4th / 5th decade
- M>F
- No concomitant OA knee
- Symptomatic —> Meniscectomy

Concomitant OA knee (Secondary degenerative):
- Older patients
- Symptoms may / may not related to meniscus lesion
- Very common incidental finding in MRI with patients suffering from concomitant OA knee
- Caution against non-selected treatment of “incidental” meniscus lesion found in MRI in patients suffering from significant OA

Question 36

Management of Meniscal injury

Answer 36

1. Conservative / Oberservation
   - asymptomatic
   - symptoms mild + compatible with acceptable function
   - understand that lesion will progress with time
   - for a short period of time to allow spontaneous healing
2. Surgery
   - **Meniscal repair (Standard)
   —> if have **healing potential
   —> young adults

• **Meniscectomy
  —> tears **not salvagable even repair is attempted (low / no healing potential)
  —> **symptomatic
  —> loss of meniscus tissue will lead to **accelerated OA
  —> middle age and elderly patient (meniscus are degenerative)
• ***Meniscus transplant
  —> symptomatic + significant loss of meniscus tissue
  —> N/A in HK ∵ lack of sizeable fresh meniscus allograft bank

Indications for surgery:
1. Acute locked knee
2. Persistent S/S of meniscal tear +/- positive radiological findings

Effect of total meniscectomy:
- Increase contact stress 200 - 300%
- Decreased contact area by 75%
- Loss of propriocetive function from encapsulated mechanoreceptors
- 50% of patients after partial meniscectomy
—> Squaring of the condyle
—> Joint space narrowing
—> Genu varum (medial)
—> Peripheral ridge or osteophyte

Question 37

Patella

Answer 37

Patella-femoral joint:
- Joint between Patella and Trochlea (Anterior surface of distal femur)

Biomechanics:
- Pull of Quadriceps —> Lateral displacing force (always) on patella —> Destabilising force —> Intrinsic instability of patella
- Aggravated by bone abnormalities:
—> Excessive genu valgus
—> Internal rotation deformity of distal femur (excessive femoral anteversion)
—> Lateralisation of tibial tuberosity (***compensatory tibial external torsion)

Local factors:
1. **Limb alignment (coronal + rotational)
2. **Patella alta (aka High riding patella)
3. ***Soft tissue imbalance in retinaculum (MPFL injury + Lateral structure tightness)
4. Muscles wasting (Vastus medialis obliquus)
5. Joint geometry: Trochlea dysplasia

Systemic factors:
1. Generalised ligamentous laxity
2. Neuromuscular disease

Kinematics:
- Terminal extension —> Patella is ***proximal to trochlea —> not articulating
- 20-30o knee flexion —> Patella starts to articulate with trochlea under effect of MPFL
- Further knee flexion —> contact surface area + PFJ pressure ↑

***MPFL:
- Important stabiliser in extension + early knee flexion
- Medial side of distal femur to Medial upper surface of patella

***Quadriceps tendon tension + Normal bony anatomy of trochlea and patella:
- Important stabiliser in mid + deep knee flexion
- Create a posterior push of patella on distal femur

Question 38

Patellar dislocation

Answer 38

Natural history:
- Incidence: 5.8/ 100,000
- Highest in the second decades
- Recurrence rate: 15-44%
—> young female, positive family history, minor trauma
—> ***50% if experience a subsequent dislocation (∵ MPFL already ruptured)
- Up to 55% failed to return to sports

Classification:
1. Traumatic / Congenital
2. Lateral (commonest) / Medial (usually iatrogenic)
3. Acute (1st time) / Recurrent / Habitual (Involuntary during flexion of knee, spontaneously reduce upon extension) / Chronic

Mechanism of injury:
- Indirect injury when the body rotates around a planted foot with subsequent twisting injury to the knee
- Direct blow to the knee

S/S:
- Pain
- **Immediate swelling of knee
- Feeling of “Dislocation of Knee”
- Possible past history of patellar dislocation
- Look for Possible **Osteochondral Fracture (~25%) —> may present as loose body —> predispose to potential accelerated OA

P/E:
- Possible obvious deformity
- Gross knee swelling
- Bruise over medial side of knee
- Localised tenderness +/- palpable defect over medial para-patellar retinaculum
- **J-sign (sign of abnormal patellar tracking)
- **Apprehension sign (sign of patellar instability)
- ***Q-angle (sign of concomitant bony abnormality, reflect amount of bony abnormality)

J-sign:
- Patient seated with knee bent
- Instruct patient to **straighten the knee while observing patellar tracking
- Patellar deviation **laterally in “J” shape with knee extension
—> J-sign +ve
—> indicate patellar **maltracking + underlying **trochlear dysplasia

Apprehension test:
- Examiner holds relaxed knee in 20 to 30 degree of flexion (patella start to articulate with trochlea)
- Manually sublux patella **laterally
- Patient will feel **pain and ***impending dislocation —> try to stop the examiner

Q-angle:
- Angle formed by line from ASIS to central patella + second line from central patella to tibial tubercle
—> Reflect direction of **Quadricep pull + **Patella tendon
—> Show amount of lateral displacement force experienced by patella
—> ↑ Q-angle ↑ risk for patellar subluxation
—> M: 14+/-3, F: 17+/-3
—> ↑ by: Genu valgum, Increased femoral anteversion, External tibial torsion, Laterally positioned tibial tuberosity

Question 39

Traumatic vs Chronic patellar dislocation

Answer 39

Traumatic:
- Common
- Accounts for 3% of all knee injuries
- **Lateral always
- With sport / significant trauma: 50-60%
- ADL without significant injury: 40-50%
- Many patients had **underlying developmental abnormality of bone (e.g. patellar alta, increased Q-angle, increased tibial tuberosity-trochlear groove distance, trochlear dysplasia, etc.)

Congenital:
Surgery performed **ASAP
- Uncommon
- Familial + Bilateral often
- Accompanied by other abnormalities, esp. arthrogryposis multiplex congenita, Down’s syndrome
- **Persistent + ***Irreducible dislocation (i.e. Chronic dislocation)

Question 40

Acute patellar dislocation

Answer 40

• ***15-50% will develop recurrent patellar dislocation (∵ MPFL already ruptured)
• MPFL almost ***always ruptures in acute patellar dislocation
• ***Osteochondral fracture in 39%
• Female 10-17 yo highest risk for 1st time acute patellar dislocation

History:
1. Occur with / without significant injury
—> Significant injury: typically low energy
—> Without significant injury: e.g. Attempt to pick thing from floor
2. **Pain
3. **Evidence of dislocation
- Giving way
- Knee cap pop / clink in and out of place
- Abnormal shape of knee
4. ***Spontaneous reduction when knee extended

Treatment:
Conservative treatment
- **CR if required
- **Long leg cylinder with knee in full extension for 3 weeks
- ***Patellar brace for 3 weeks
- Active Quadriceps strengthening exercise

Early surgery only indicated:
1. Presence of ***Osteochondral fracture
2. Persistent patellar subluxation / dislocation despite CR

Question 41

Recurrent patellar dislocation

Answer 41

• ***Always have repeated patellar dislocation / symptoms of patellar instability (i.e. apprehension)
• Repeated patellar dislocation will lead to **progressive chondral damage —> accelerated symptomatic **OA (esp. in patello-femoral joint)

History:
1. **Repeated patellar dislocation
2. Confirmed dislocation previously
3. Subjective feeling that patella move in and out of trochlea
4. +/- Pain (until late stage with OA change)
5. **Apprehension
- worry that knee cap is coming out (even if patella is reduced)
- loss of confidence in walking downslope, downstairs, participation in sports

Treatment:
- Surgical stabilisation (***MPFL reconstruction) is advised

(If significant bony developmental problem —> bony operation will be required:
- Tibial tubercle transfer (Fulkerson osteotomy) / Trochleoplasty)

Question 42

Management of Patellar dislocation

Answer 42

1. Conservative treatment
   - **CR if required
   - **Long leg cylinder with knee in full extension for 3 weeks
   - **Patellar brace for 3 weeks
   - **Active Quadriceps strengthening exercise
2. Surgery
   - **Persistent subluxation / dislocation of patella despite CR
   - **Osteochondral fracture
   —> Potential loose body
   —> Sizeable bony component which allows reduction and fixation

Question 43

Osteoarthritis of knee

Answer 43

Varus deformity:
- More force transmitted to medial compartment
—> Medial compartment degenerate more rapidly

Investigations (From MSS03):
1. Plain radiographs (Kellgren Lawrence classification)
- **narrowing of joint space
- **marginal osteophyte
- **subchondral sclerosis
- **subchondral cyst
- body contour change / defect

2. MRI
   - Meniscal tear (cannot be seen on X-ray)
   —> traumatic
   —> degenerative
   - **Loose bodies
   - **Cysts
   —> Baker’s cyst / Popliteal cyst
3. Blood tests
   - **normal white cell count
   - **normal ESR (↑ ESR / CRP —> inflammatory rather than degenerative causes)
   - normal bone profiles (Ca, PO4, alkaline phosphatase)
4. Joint aspiration
   - clear straw colour
   - total cell count <1000 / mm3
   - **gram smear -ve, culture -ve
   - **crystals -ve
   —> urate crystal (Gouty arthritis)

Question 44

(Ligamentous laxity (From SpC O/T Bedside))

Answer 44

Beighton Hypermobility Score:
- quantify joint laxity and hypermobility
- 9 point system
- threshold for joint laxity in a young adult: 4-6
- a score above 6 indicates hypermobility

Domains:
1. Little finger (L + R)
- passive dorsiflexion beyond 90o (1 point)

2. Thumb (L + R)
   - passive dorsiflexion to the flexor aspect of the forearm (1 point)
3. Elboe (L + R)
   - hyperextends beyond 10o (1 point)
4. Knee (L + R)
   - hyperextends beyond 10o (1 point)
5. Forward flexion of trunk with knees full extended
   - palms and hands can rest flat on the floor (1 point)

Question 45

Grade 3 laxity (No end point) Multi-ligament injury (SpC Revision)

Answer 45

• Knee dislocation / previous dislocation
• 50% chance of acute vascular injury with intimal tear —> Delayed thrombosis of popliteal artery
• Check distal pulses / ABI repeatedly
• Check for compartment syndrome

Question 46

Summary (Self notes)

Answer 46

Haemoarthrosis:
- ACL deficiency
- Osteochondral fracture
- Patellar dislocation

Early surgery required:
- Avulsion fracture of cruciate ligament
- Displaced meniscus tear (esp. bucket handle) with acute locking
- Grade 3 Collateral ligament injury

ACL tear:
- Haemarthrosis
- No rush to repair, do it as elective
- No repair, only reconstruction using tendon graft

Meniscus tear:
- Locking: loss of terminal passive extension
- Acute locking: persistently displaced meniscus fragment
- Intermittent locking: displaceable meniscus tear
- Traumatic: Repair ASAP
- Degenerative (underlying developmental problem e.g. discoid meniscus): Observe / Meniscectomy if symptomatic
- Repair / Meniscectomy / Meniscus transplant

Patellar dislocation:
- Haemarthrosis
- Acute patellar dislocation: Traumatic, MPFL always rupture
- Chronic patellar dislocation: Congenital, persistent + irreducible dislocation, surgery ASAP
- Developmental problem: patellar alta, increased Q-angle, increased tibial tuberosity-trochlear groove distance, trochlear dysplasia
- CR / Long leg cylinder / Patellar brace / Quadriceps strengthening
- Surgery: Osteochondral fracture / Persistent subluxation / Dislocation of patella despite CR