**Core Concept**
The stability of the knee joint is primarily maintained by a combination of static and dynamic stabilizers. The static stabilizers include the ligaments, such as the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL), while the dynamic stabilizers include the surrounding muscles and their tendons.

**Why the Correct Answer is Right**
The correct answer is **C. Ligaments**. The ligaments play a crucial role in maintaining the stability of the knee joint by providing resistance to various forces, such as valgus, varus, and rotational stresses. The ACL and PCL are particularly important, as they prevent excessive forward and backward movement of the tibia relative to the femur. The MCL and LCL provide stability against valgus and varus stresses, respectively.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the joint capsule, although it provides some degree of stability, is not the primary stabilizer of the knee joint.
* **Option B:** This option is incorrect because the muscles and tendons do contribute to the stability of the knee joint, but they are not the main stabilizers.
* **Option D:** This option is incorrect because the bones themselves do not provide significant stability to the knee joint; rather, it is the ligaments and other soft tissues that maintain joint stability.

**Clinical Pearl / High-Yield Fact**
The knee joint is often described as a "hinge joint" due to its limited rotational movement, but it also allows for some degree of flexion and extension. The ACL and PCL are often injured in sports that involve sudden stops, changes in direction, or landing from jumps, making knee ligament injuries a common concern in orthopedic medicine.

**Correct Answer:** C. Ligaments