Overview
This lecture covers the anatomy of the human knee, focusing on the anterior cruciate ligament (ACL), its role, common injuries, surgical repair options, and prevention strategies.
Human Knee Anatomy
- The knee contains the femur (thigh bone), tibia (medial shin bone), fibula (lateral shin bone), and patella (kneecap).
- The medial collateral ligament (MCL) is on the inner side of the knee; the lateral collateral ligament (LCL) is on the outer side.
- The MCL and LCL are extra-articular ligaments, located outside the joint capsule.
- Cartilage in the knee cushions the joint but can wear down, leading to arthritis.
Cruciate Ligaments: ACL & PCL
- The ACL (anterior cruciate ligament) and PCL (posterior cruciate ligament) cross inside the knee joint.
- The ACL prevents the tibia from sliding forward and limits internal rotation and hyperextension.
- The PCL prevents the tibia from sliding backward.
ACL Injuries and Diagnosis
- Ligaments connect bone to bone, stabilize joints, and define joint range of motion.
- The ACL is commonly injured by excessive forward movement, rotation, or hyperextension.
- 70% of ACL tears are non-contact injuries, often from awkward landings or sudden twists.
- Examination includes the "anterior drawer test" to assess ACL integrity.
- ACL injuries range from microtears (treated with physical therapy) to complete tears (may require surgery).
ACL Reconstruction Options
- Autograft uses a patient's own tissue, usually from the hamstrings (semitendinosus tendon) or patellar tendon.
- Hamstring grafts are strong but require careful fixation; may result in temporary hamstring weakness.
- Patellar tendon grafts include bone plugs for better anchoring, but may cause anterior knee pain or tendonitis.
- Allograft uses donor tissue (usually Achilles or patellar tendon); avoids local pain but has higher failure risk.
ACL Tear Prevention
- Neuromuscular training improves coordination and communication between nerves and muscles.
- Prevention exercises include plyometrics (explosive movements), landing drills, balancing, and strength training.
- Balanced strength between quadriceps and hamstrings lowers ACL injury risk.
- Proper training can reduce ACL injury risk by over 50%.
Key Terms & Definitions
- ACL (Anterior Cruciate Ligament) — ligament inside the knee that prevents the tibia from sliding forward.
- PCL (Posterior Cruciate Ligament) — ligament preventing the tibia from sliding backward.
- MCL (Medial Collateral Ligament) — ligament on the inner knee.
- LCL (Lateral Collateral Ligament) — ligament on the outer knee.
- Autograft — tissue graft from the patient’s own body.
- Allograft — tissue graft from a donor body.
- Plyometrics — exercises involving rapid, powerful movements.
Action Items / Next Steps
- Review knee ligament anatomy and their functions.
- Practice or observe the anterior drawer test.
- Incorporate neuromuscular training and balanced strength exercises into workout routines.