Knee Injury Patterns: Most Commonly Damaged Structures

The knee is the largest, most complex joint, bearing high loads with mobility. Injury patterns differ by mechanism (contact vs non-contact), sport, age, and sex.

Most Frequently Injured Structures

Structure	Mechanism	Population	Key Features
ACL (Anterior Cruciate Ligament)	Non-contact: deceleration, pivoting, landing (valgus + rotation). Contact: direct blow.	Female athletes 2–8× higher risk (biomechanics, hormones, anatomy). Soccer, basketball, skiing, football.	"Pop," immediate swelling (hemarthrosis), instability. Often with MCL/meniscus (unhappy triad).
Medial Meniscus	Twisting on flexed, weight-bearing knee. Degenerative tears >40 yrs.	All ages; medial > lateral (less mobile).	Joint line pain, catching, locking, effusion.
MCL (Medial Collateral Ligament)	Valgus stress (blow to lateral knee).	Contact sports (football, hockey, wrestling).	Medial pain, tenderness, opening on valgus stress test. Grades I–III.
Lateral Meniscus	Similar to medial; often with ACL tear.	Young athletes.	Lateral joint line pain.
Patellar Tendinopathy	Overuse (jumping, loading).	Volleyball, basketball ("jumper's knee").	Inferior pole patella pain, worse loading.
Patellofemoral Pain (PFPS)	Maltracking, overload, muscle imbalance.	Young females, runners.	Anterior knee pain, stairs, sitting.
Articular Cartilage	Trauma (osteochondral defect), degeneration (OA).	All ages.	Pain, swelling, mechanical symptoms.
PCL (Posterior Cruciate Ligament)	Dashboard injury (posterior tibial translation), hyperflexion.	MVC, contact sports.	Often missed; posterior drawer test.

Sex Differences

• Females: ↑ACL, PFPS, patellar instability (wider pelvis → ↑Q-angle, hormonal ligament laxity, neuromuscular control).
• Males: ↑PCL, high-energy trauma, contact injuries.

Diagnosis & Management

• Clinical exam (Lachman, pivot shift, McMurray, valgus/varus stress, effusion).
• MRI gold standard for soft tissue.
• Treatment: ACL – recon (young/active) vs rehab (low demand). Meniscus – repair (peripheral, young) vs partial meniscectomy. MCL – usually non-op (brace/PT). Cartilage – microfracture, OATS, MACI, replacement.

Prevention: Neuromuscular training (FIFA 11+, PEP) reduces ACL risk 50%+ in females.