Medial Meniscus Tear: This is a common injury that occurs when the knee is twisted, especially in a weight-bearing position. The meniscus is a cartilage structure in the knee joint that can be damaged by a sudden twisting motion, leading to pain, swelling, and limited mobility.

Ligament Sprain (MCL or ACL): The medial collateral ligament (MCL) and anterior cruciate ligament (ACL) are commonly injured in twisting knee injuries. These sprains can cause pain, instability, and swelling in the knee.
Knee Contusion or Bruise: A fall down the steps can cause a direct blow to the knee, resulting in a contusion or bruise. This can lead to pain, swelling, and limited mobility.
Patellofemoral Pain Syndrome: This condition is characterized by pain in the front of the knee, usually around the kneecap. It can be caused by a twisting injury or a fall onto the knee.

Fracture (e.g., Tibial Plateau or Patella): Although less common, a fracture of the tibial plateau or patella can occur with a twisting injury, especially if there is a high-energy mechanism of injury. Missing this diagnosis can lead to serious complications, such as arthritis or chronic pain.
Vascular Injury: A twisting injury can cause damage to the blood vessels in the knee, leading to ischemia or compartment syndrome. This is a medical emergency that requires prompt attention.
Neurological Injury (e.g., Peroneal Nerve Damage): The peroneal nerve runs down the outside of the knee and can be damaged in a twisting injury. This can cause numbness, tingling, or weakness in the foot or ankle.

Osteochondritis Dissecans: This is a rare condition where a piece of cartilage and bone in the knee joint becomes damaged, leading to pain and limited mobility.
Knee Dislocation: Although rare, a knee dislocation can occur with a high-energy twisting injury. This is a medical emergency that requires prompt attention to prevent serious complications.