Pathogenesis (development of disease)
Meniscal Injuries
Meniscal contusion is usually due to mild knee rotation.
Acute meniscal tear with or without extension/flexion inhibition may be due to torsional trauma (knee twisting). Degenerative change of the meniscus is often present.
Ligament injuries
Knee joint injuries involving collateral/cruciate ligaments are usually due to trauma.
Collateral ligament strain is usually due to varus stress or valgus stress:
- Varus stress (O-B adjustment): forces in the direction of the joint axis from the inside to the outside → compression of the medial parts of the joint (“oriented toward the center of the body”) and stretching or tearing of the lateral ligament structures.
- Valgus stress (X-B setting): forces in the direction of the joint axis from the outside to the inside → compression of the lateral joint components (“facing away from the center of the body”) as well as stretching or tearing of the medial ligament structures.
A rupture of the lateral ligament is usually due to varus stress or valgus stress, or even to an opponent’s impact.
Cruciate ligament injuries are most often caused by valgus stress, which means the knee gets into the X-B position: it rotates inward while the body’s center of gravity is behind the knees and the legs are loaded unevenly. This typically happens when landing after a jump, abruptly changing running direction, stopping suddenly, or turning.
An anterior and posterior cruciate ligament rupture is due to a torsional injury – in fact, there is usually no opponent action.
Cartilage injuries
A cartilage contusion (cartilage bruise) is usually the result of a crush or impact; typically, deterioration occurs with continued loading.
Cartilage damage or flake fracture (osteochondral lesions; avulsion fracture or shear fracture) is usually the result of more severe compression or impact.
Acute rupture of articular cartilage usually results from trauma, especially impact trauma.Chronic degenerative loading results.
Combination injuries
Complex mediolateral joint injuries (“Unhappy Triad”) due to massive knee rotational trauma.In an Unhappy Triad injury, a medial meniscal lesion, anterior cruciate ligament rupture, and tear of the medial collateral ligament are present.
Luxations
In patellar luxation (knee joint injury in which the kneecap (patella) jumps out of its guide (luxation)), the following forms can be distinguished:
- Acute traumatic patellar luxation
- Acute habitual patella (sub)luxation – favored by various predisposing factors such as changes in the shape of the patella or joint, knock knees or hyperextensibility of the knee joint
- Recurrent patella (sub)luxation
- Congenital patella luxation
Knee dislocation occurs due to the counteracting strong force on the lower leg and thigh.
Chronic knee joint injuries are mainly due to overuse and repetitive (micro) trauma.
Etiology (causes)
Biographical causes
- Occupations – occupations with persistent or frequently recurring activities that place above-average stress on the knee joints (e.g., tile setters; soccer players) [meniscus damage].
Behavioral causes
- Physical activity
- Sports that put a strain on the knees, such as soccer, handball, basketball, field hockey, or skiing
- Ski bindings set too hard! Knee injuries are twice as common in women as in men; experts call for the introduction of a corresponding correction factor for women, which reduces the binding standard
Other causes
- Accidents