ACUTE KNEE INJURIES: MAKING THE DIAGNOSIS

Richard A. Lemon, M.D.
Orthopaedic Surgeon

COMMON SITE OF INJURY IN MANY RECREATIONAL SPORTS
•	Skiing:  
	1/3 of all knee injuries
•	Basketball:
	7:1; female:male
•	Soccer
•	Softball
•	Volleyball
•	Wrestling
•	Football

HISTORY

•	Mechanism of Injury
•	Valgus stress
•	Hyperextension
•	Direct blow
•	Twisting

•	Swelling
•	Acute: 4-6 hours = hemarthrosis
•	Hemarthrosis: 70% = ACL tear
•	>24 hours = effusion

PHYSICAL EXAMINATION 

•	Anatomy
•	Ligaments: ACL, PCL, MCL, LCL
•	Meniscus: medial, lateral
•	Tendon: quadriceps, patellar, medial retinaculum
•	Bone: femur, tibia, patella

•	Ligaments
•	ACL: Lachman, Anterior Drawer, Pivot Shift
•	PCL: Reverse Lachman, Posterior Drawer, Reverse Pivot
•	MCL: 0 and 30° (30° isolates MCL)
•	LCL: 0 and 30° (30° isolates MCL)

•	Meniscus
•	Joint line tenderness: 95%
•	Pain at limits of flexion: 65%
•	Pain at limits of extension: 40%
•	McMurray test: 33%

•	Tendons
•	Quadriceps:  defect above patella
•	Patellar:  high riding patella

DIAGNOSTIC STUDIES
•	X-rays
•	MRI
•	Aspiration
•	Arthrogram
•	Bone scan
•	CT scan

•	X-rays: ALWAYS Four Views!
•	AP
•	Lateral
•	Tunnel or notch
•	Patella: Sunrise, Merchant, Laurin, Hughston

•	MRI
•	Menisci, articular cartilage
•	Effusion
•	ACL, PCL
•	MCL, LCL
•	Bony abnormalities
-	Fractures; Osteochondritis Dessicans; Bone Contusion

•	Role of Aspiration
•	Infection
•	Hemarthrosis vs. Effusion

CASE PRESENTATIONS

•	CASE #1
•	16-year-old female basketball player
•	Running, planted foot
•	Heard “pop”
•	Knee buckled and she fell to the floor
•	Knee felt “loose”
•	Immediate swelling

Injury = ___________________________

•	CASE #2
•	26-year-old male basketball player
•	Running, trips on teammate
•	Falls directly onto knee

Injury = ___________________________

•	CASE #3
•	16-year-old female basketball player
•	Twisted knee
•	Felt knee buckle
•	Extended knee and felt it “pop back in”

Injury = ___________________________

•	CASE #4
•	16-year-old male basketball player
•	Twisted knee; Played rest of game
•	Swelling over 24-48 hours
•	MJL tenderness

Injury = ___________________________
•	
CASE #5
•	36-year-old male basketball player
•	Twisted knee
•	Unable to straighten leg
•	Swelling over next 24 hours
•	MJL tenderness
•	Lacks 10 degrees of extension

Injury = ___________________________

•	CASE #6
•	16-year-old male football player
•	Valgus blow by another player
•	No swelling
•	MJL tenderness
•	MCL tenderness
•	Slight MCL laxity

Injury = ___________________________

•	CASE #7
•	20-year-old male basketball player
•	Hyper-extends knee
•	Teammate falls on knee
•	Unable to move leg
•	Acute swelling
•	Obvious deformity

Injury = ___________________________

•	CASE #8
•	35-year-old male
•	True locking for 10 years
•	No previous trauma

Injury = ___________________________

•	CASE #9
•	36-year-old male firefighter
•	Felt “pop” while lifting weights
•	Immediate, huge swelling
•	Palpable defect below patella

Injury = ___________________________

SUMMARY

•	History
•	The patient will tell you what they injured!
•	Worker’s Compensation: Is the history consistent with the injury?

•	Physical Exam
•	Hemarthrosis = ACL tear, unless proven otherwise
•	Relaxed patient = good exam
•	Examine all structures

•	Diagnostic Studies
•	Four views of knee
•	MRI when appropriate

•	Avoid
•	Aspiration
•	Prolonged use of knee immobilizer
•	Prolonged use of crutches
•	Prolonged absence from work

•	Encourage
•	Early motion
•	Referral to orthopaedics
•	Early return to work

QUESTIONS?