Anterior cruciate ligament (ACL) - controls rotational movement and prevents forward movement of the tibia in relation to the femur. Runs between attachments on the front (hence anterior cruciate) of the tibial plateau and the posterolateral aspect of the intercondylar notch of the femur
Posterior cruciate ligament (PCL) - prevents forward sliding of the femur in relation to the tibial plateau. Runs between attachments on the posterior part (hence posterior cruciate) of the tibial plateau and the medial aspect of the intercondylar notch of the femur.
Medial collateral ligament - prevents lateral movement of the tibia on the femur when valgus (away from the midline) stress is placed on the knee. Runs between medial epicondyle of the femur and the anteromedial aspect of the tibia. Also has a deep attachment to the medial meniscus
Lateral collateral ligament - prevents medial movement of the tibia on the femur when varus (towards the midline) stress is placed on the knee. Runs between lateral epicondyle of the femur and head of the fibula.
Menisci: the medial and lateral menisci are located within the knee joint, attached to the tibial plateau. They help to protect the articular surfaces by absorbing some of the forces transmitted through the knee. They also help to stabilise and lubricate the knee.
If there was trauma, what exactly happened? If injury occurred in sport or an accident get a precise history of the mechanism. Was there a direct blow causing vulgus or varus stress? Was there a twisting motion?
Was there any sound? A 'popping' or 'snapping' sound may suggest rupture of a ligament.
Did the knee swell immediately, gradually, or not at all? Rapid swelling (0-2 hours) suggests haemarthrosis which may be due to e.g. ACL or PCL rupture, patellar dislocation. Gradual swelling (6-24 hours) suggests an effusion which may be due to meniscal injury.
The medial and lateral collateral ligaments (MCL and LCL)
are tested by stressing the knee into valgus and varus: this is best done by tucking the patient’s foot under your arm and holding the extended knee firmly with one hand on each side of the joint; the leg is then angulated alternatively towards abduction and adduction. This is called valgus and varus stress tests.
are tested by examining for abnormal gliding movements in the antero-posterior plane. With both knees flexed 90 degrees and the feet resting on the couch, the upper tibia is inspected from the side; if its upper end has dropped back, or can be gently pushed back, this indicates a tear of the posterior cruciate ligament (the 'sag sign').
With the knee in the same position, the foot is anchored by the examiner sitting on it (provided this is not painful): then, using both hands, the upper end of the tibia is grasped firmly and rocked backwards and frontward to see if there is any antero-posterior glide ( the drawer test )
Lachman test- is more sensitive but this is difficult if the patient has big thighs (or the examiner has small hands). The patient’s knee is flexed 30 degrees; with one hand grasping the lower thigh and the other the upper part of the leg, the joint surfaces are shifted backwards and forwards upon each other. If the knee is stable, there should be no gliding.
This is the classic test for a torn meniscus and is based on the fact that the loose tag can sometimes be trapped between the articular surfaces and then induced to snap free with a palpable and audible click. The knee is flexed as far as possible; one hand steadies the joint and the other rotates the leg medially and laterally while the knee is slowly extended. The test is repeated several times with the knee stressed in valgus or varus feeling and listening for the click.
The patellofemoral joint is examined separately: The size, shape and position of the patella are noted. The bone is felt first on its anterior surface and then along is edges and at the attachments of the quadriceps tendon and the patellar ligament. Much of the posterior surface is accessible to palpation if the patella is pushed first to one side and then to the other: tenderness suggests synovial irritation or articular cartilage softening moving the patella up and down while pressing it lightly against the femur (the friction test') causes painful grating if the central portion of the articular cartilage is damaged.
Antero-posterior, lateral and sometimes patello-femoral (or skyline) and intercondylar or tunnel views are needed. The antero-posterior view should be taken with the patient standing. Stress films in valgus and varus are essential for diagnosing collateral ligament tears. Loose bodies also can e detected.