Musculoskeletal system and connective tissue (M00-M99).
- Arthritis (inflammation of a joint), unspecified.
- Gonarthrosis (knee joint arthrosis)
- Hypertrophic (enlarged) Hoffa fat body (corpus adiposum infrapatellare) – this is located in the knee joint between condyle tibiae (tibial plateau), ligamentum patellae (patellar ligament) and the lower edge of the patella (kneecap).
- Meniscus cyst – encapsulated cavity in the area of the meniscus.
- Osteochondrosis dissecans – disease more common in adolescents leading to circumscribed aseptic bone necrosis below the articular cartilage, which may end with rejection of the affected bone area with the overlying cartilage as a free joint body (joint mouse); this often causes irritation
- Retropatellar osteoarthritis – osteoarthritis (degenerative joint disease) in the femoropatellar joint (consists of the kneecap (patella) and the lower portion of the thigh bone (femur)) between the patella and trochlea femoris (articulation surface of the femur with the patella).
Injuries, poisoning, and other consequences of external causes (S00-T98).
- Acute traumatic patellar dislocation
- Acute habitual patella (sub)luxation
- Ligament injuries
- Fractures (fractures) in the knee joint, unspecified.
- Free joint bodies
- Hypertrophied plica mediopatellaris (a fold of synovium (inner synovial membrane) in the knee joint that protrudes into the interior of the knee joint)
- Bone/cartilage injuries in the area of the knee joint, unspecified.
- Congenital patellar luxation – luxation caused by genetic malformations.
- Lesion of the medial collateral ligament
- Meniscal injuries
- Recurrent patella (sub)luxation
- Unhappy triad injury – medial meniscal lesion, anterior cruciate ligament rupture, and medial collateral ligament tear.
