## Knee Joint Stability Structures ### Menisci Anatomy **Key Point:** The medial meniscus is **C-shaped** (or O-shaped) and covers a larger surface area of the tibial plateau compared to the lateral meniscus, which is more **O-shaped** (or comma-shaped). The medial meniscus is more firmly attached to the joint capsule and MCL, making it more prone to entrapment injuries. ### Popliteus Muscle **High-Yield:** The popliteus is the only muscle that **internally rotates the tibia** on a fixed femur (or externally rotates the femur on a fixed tibia). It originates from the lateral femoral condyle and inserts on the posterior tibial surface. This action is crucial for "unlocking" the knee from full extension. **Clinical Pearl:** The popliteus is innervated by the tibial nerve and is tested clinically with the popliteal sign. ### Iliotibial Band and Tensor Fasciae Latae **Warning:** The iliotibial (IT) band inserts on the **lateral tibial condyle** (Gerdy's tubercle), **NOT** on the tibial tuberosity. The tibial tuberosity is the insertion point of the patellar ligament (quadriceps tendon). This is a common anatomical confusion point. | Structure | Origin | Insertion | Function | |-----------|--------|-----------|----------| | Tensor fasciae latae | ASIS, iliac crest | Gerdy's tubercle (lateral tibia) | Hip flexion, abduction, knee extension | | Patellar ligament | Patella | Tibial tuberosity | Knee extension | ### Pes Anserinus **Mnemonic:** **SGS** = Sartorius, Gracilis, Semitendinosus (the three muscles forming the pes anserinus on the medial tibia). The gracilis inserts on the medial tibial condyle as part of this structure. ### Why the Correct Answer is Wrong The IT band inserts on **Gerdy's tubercle** (lateral tibial condyle), not the tibial tuberosity. The tibial tuberosity is the insertion of the patellar ligament, not the IT band. This is the only false statement.
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