Malalignment arthritis is joint arthritis that is strongly influenced by “off-axis” limb or joint alignment. It most commonly refers to knee osteoarthritis that progresses faster in one compartment because load is unevenly distributed. Clinicians use the term when alignment is a meaningful driver of pain, function limits, and cartilage wear. It is discussed in orthopedics, sports medicine, and physical therapy when planning evaluation and management.

Post-traumatic arthritis is arthritis that develops after a joint injury. It commonly affects the knee, ankle, hip, and shoulder after fractures, ligament tears, or cartilage damage. It is used in orthopedic and sports medicine settings to describe joint pain, stiffness, and function loss linked to prior trauma. It can appear months to years after an injury, and its course varies by person and injury type.

Knee arthrofibrosis is an abnormal buildup of scar-like tissue in and around the knee joint. It can make the knee feel stiff, painful, or difficult to fully bend or straighten. It is most commonly discussed after knee surgery or significant knee injury. Clinicians use the term to describe a stiffness problem that is more than routine post-injury tightness.

A Popliteal cyst is a fluid-filled swelling that forms behind the knee. It is commonly called a Baker’s cyst. It usually relates to extra joint fluid from inflammation or injury inside the knee. The term is used in orthopedics, sports medicine, radiology, and physical therapy documentation.

A Baker cyst is a fluid-filled swelling that forms behind the knee. It is also called a popliteal cyst. It often develops when the knee joint produces extra fluid due to irritation inside the joint. The term is commonly used in orthopedics, sports medicine, physical therapy, and imaging reports.

Pigmented villonodular synovitis is a joint lining disorder that can cause pain, swelling, and stiffness. It involves abnormal overgrowth of synovium, the tissue that lines joints, bursae, and tendon sheaths. It most often affects large joints like the knee and can mimic more common causes of knee pain. The term is used in orthopedics, sports medicine, radiology, and pathology to describe this specific synovial condition.

PVNS knee refers to pigmented villonodular synovitis affecting the knee joint. It is a condition where the synovium (the joint lining) grows abnormally and can become inflamed and thickened. It is commonly discussed in orthopedics, sports medicine, rheumatology, radiology, and physical therapy when evaluating persistent knee swelling and pain. Many clinicians also group PVNS under the broader term **tenosynovial giant cell tumor (TGCT)**.

Synovial chondromatosis is a joint disorder where the synovium (the joint lining) forms small cartilage nodules. These nodules can break loose and become “loose bodies” that move inside the joint. It is most often discussed in orthopedic care when evaluating joint pain, swelling, catching, or locking. The knee is a common location, but other joints can be affected.

OCD knee usually refers to **osteochondritis dissecans (OCD) of the knee**. It describes a problem where **bone just under the knee cartilage** becomes injured and may affect the overlying cartilage. It is commonly discussed in **sports medicine, orthopedics, and physical therapy** when evaluating knee pain in active people. It can involve monitoring, rehabilitation, and sometimes surgery, depending on the lesion.

Osteochondritis dissecans is a joint condition where a patch of bone just under the cartilage becomes injured. It can affect the overlying cartilage, sometimes leading to a partially detached or fully loose fragment. It is most often discussed in sports medicine and orthopedics in relation to the knee. It can also occur in other joints, such as the ankle or elbow.