IT band friction syndrome is a common cause of pain on the outside (lateral side) of the knee. It involves irritation where the iliotibial (IT) band passes near the outer end of the thigh bone (femur). It is most often discussed in sports medicine and physical therapy, especially for running and cycling knee pain. Clinicians use the term to describe a pattern of symptoms, exam findings, and contributing mechanics.

Semimembranosus bursitis is inflammation of a small fluid-filled sac (a bursa) near the back-inner (posteromedial) side of the knee. A bursa normally reduces friction where tendons and muscles glide over bone and other tissues. When inflamed, it can cause localized pain, swelling, or a feeling of fullness behind the knee. The term is commonly used in orthopedics, sports medicine, radiology, and physical therapy when evaluating posteromedial knee pain or a popliteal-area lump.

Infrapatellar bursitis is inflammation of a small fluid-filled sac (a bursa) located below the kneecap. It typically causes pain, swelling, or tenderness at the front of the knee near the patellar tendon. It is commonly discussed in sports medicine, orthopedics, and physical therapy when evaluating anterior knee pain. It may be related to repetitive kneeling, overuse, direct pressure, or less commonly infection or inflammatory disease.

Prepatellar bursitis is inflammation of the small fluid-filled sac in front of the kneecap. It commonly causes swelling and tenderness over the front of the knee. It is often discussed in orthopedics and sports medicine when knee pain is linked to kneeling, a direct blow, or infection. Clinicians use the term to describe a specific, surface-level source of anterior (front) knee symptoms.

Pes anserine tendinopathy is irritation or degeneration of tendons on the inner (medial) side of the knee. It involves the “pes anserinus,” where three thigh muscles attach to the upper shinbone (tibia). It commonly shows up as localized pain below the knee joint line, especially with activity. The term is used in orthopedics, sports medicine, and physical therapy when evaluating medial knee pain.

Pes anserine bursitis is inflammation of a small fluid-filled sac (a bursa) on the inner side of the knee. It typically causes tenderness and aching pain below the medial (inner) joint line on the shinbone (tibia). The bursa sits under the “pes anserinus” tendons, where three thigh muscles attach near the knee. The term is commonly used in orthopedics, sports medicine, and physical therapy when evaluating inner-knee pain.

Patellar crepitus is a crackling, grinding, or “crunching” sensation felt or heard around the kneecap during knee movement. It is a clinical finding that can be painless or associated with discomfort. The term is commonly used in orthopedic, sports medicine, and physical therapy exams. It usually refers to friction or irregular motion in the patellofemoral joint (kneecap and thigh bone).

Patellofemoral chondrosis is a term for wear, softening, or damage of the joint cartilage in the patellofemoral joint. The patellofemoral joint is where the kneecap (patella) glides on the groove at the end of the thigh bone (femur). Clinicians use this term in imaging reports, arthroscopy findings, and clinical discussions of front-of-knee pain. It helps describe cartilage condition, not a single treatment or procedure.

Patellofemoral arthritis is arthritis that affects the joint between the kneecap (patella) and the thigh bone (femur). It involves wear, damage, or degeneration of the cartilage in the front compartment of the knee. It is commonly discussed in orthopedics, sports medicine, and physical therapy when evaluating “front of knee” pain. It can occur on its own or alongside arthritis in other parts of the knee.

Patellar fracture means a break in the patella, also called the kneecap. It is a knee injury that can affect walking, straightening the leg, and kneeling. It is commonly discussed in emergency care, orthopedics, sports medicine, and physical therapy settings. Clinicians use the term to describe the diagnosis and to guide imaging, treatment planning, and rehabilitation.