Meniscal Tear: A meniscal tear is a common injury that can occur when the knee is twisted or bent, resulting in a popping sound. The meniscus is a cartilage structure in the knee that can become damaged, leading to pain and discomfort when bearing weight.

Ligament Sprain: A ligament sprain, such as an MCL or LCL sprain, can occur when the knee is twisted or bent, resulting in a popping sound and discomfort when bearing weight.
Patellofemoral Pain Syndrome: This condition occurs when the cartilage under the kneecap becomes irritated, leading to pain and discomfort when bearing weight, especially when going up or down stairs.
Tendinitis: Tendinitis, such as quadriceps or patellar tendinitis, can cause pain and discomfort in the knee, especially when bearing weight.

Fracture: A fracture, such as a tibial plateau fracture, can occur when the knee is twisted or bent, resulting in a popping sound and severe pain. This diagnosis is critical to rule out, as a missed fracture can lead to long-term complications.
Septic Arthritis: Septic arthritis is a serious infection that can occur in the knee joint, leading to severe pain, swelling, and discomfort. This diagnosis is critical to rule out, as delayed treatment can lead to serious complications.
Osteonecrosis: Osteonecrosis, also known as avascular necrosis, is a condition where the bone tissue dies due to lack of blood supply. This diagnosis is critical to rule out, as it can lead to collapse of the bone and long-term disability.

Osgood-Schlatter Disease: This condition occurs when the patellar tendon pulls away from the tibia, leading to pain and discomfort in the knee.
Discoid Meniscus: A discoid meniscus is a rare condition where the meniscus is thicker and more prone to tearing, leading to pain and discomfort in the knee.
Plica Syndrome: Plica syndrome is a rare condition where the synovial tissue in the knee becomes inflamed, leading to pain and discomfort.