KNEE JOINT
Definition
- Hinge synovial joint between femur, tibia, and patella
Location
- Junction between thigh and leg
Articulating Surfaces
- Femoral condyles
- Tibial plateau
- Posterior surface of patella
- Covered with hyaline cartilage
Structure
- Medial and lateral condyles of femur articulate with corresponding tibial condyles
- Patella articulates with femoral trochlea
- Joint capsule surrounds joint and lined by synovial membrane
Ligaments of Knee Joint
- Anterior cruciate ligament (ACL)
- Posterior cruciate ligament (PCL)
- Medial collateral ligament (MCL)
- Lateral collateral ligament (LCL)
- Menisci → medial & lateral
Nerve Supply
- Femoral nerve → anterior aspect
- Obturator nerve → medial aspect
- Sciatic nerve → posterior aspect
Blood Supply
- Genicular branches of femoral, popliteal, and tibial arteries
Movements
- Flexion, extension
- Slight medial and lateral rotation when knee flexed
Muscle Action Sequence
- Flexion → hamstrings, gracilis, sartorius
- Extension → quadriceps femoris
- Medial rotation → semitendinosus, semimembranosus
- Lateral rotation → biceps femoris
Stepwise Anatomical Mechanism
- Flexion: hamstrings contract → tibia moves posteriorly → knee flexes
- Extension: quadriceps contract → tibia moves anteriorly → knee extends
Clinical Anatomy
- Knee dislocation → risk to popliteal artery
- ACL/PCL tear → instability
- Meniscal tears → locking or pain
- Osteoarthritis → pain, restricted movements
- Baker’s cyst → swelling at popliteal fossa