Anterior Cruciate Ligament rupture
The anterior cruciate ligament stops your shin moving forward compared to your thigh bone. Normally when you twist on the knee everything turns together. When the ligament is torn the knee buckles as you try and pivot or twist, so that you no longer trust it.
Following the injury your knee may have been painful and swollen immediately, and afterwards your knee may give way again and feel less trustworthy.
When examining there may be excessive movement found in the knee. The two main tests are called the Lachman test and the Pivot Shift test.
Posterior Cruciate Ligament rupture
The posterior cruciate ligament stops your shin bone moving backwards in relation to your thigh bone. When examined with your knee at a right angle, your shin bone will sag backwards compared to your other side or the surgeon can move it excessively.
Medial or Lateral Collateral Ligament rupture or partial tear
The medial and lateral collateral ligaments lie on either side of the knee and stop it moving too much sideways. If the medial collateral ligament is damaged there may be pain on the inner side of your knee, following the line of the ligament. The knee may feel wobbly and when examined it is painful as the surgeon pulls your leg sideways. If the lateral collateral ligament is damaged there may be pain on the outer surface of your knee, with some giving way and again when examined you may feel pain as the lower leg is moved inwards.
The meniscus or ‘footballer’s cartilage’ lies between your thigh and shin bone and acts as a shock absorber when you bear weight. You have two – one on the outer lateral side and one on the inner medial side. When the knee is examined there is specific tenderness on the joint line between the bones. There may be swelling found in the knee and sometimes the knee can transiently lock as the torn fragment gets caught.
The patella or kneecap acts to increase the leverage of your knee when straightening your leg and it slides over your thigh bone as you bend and straighten.
Your kneecap may dislocate or feel unstable following an injury, or you may describe the feeling of your kneecap dislocating repeatedly. Usually, specialist help from casualty is needed to put it back in its place if it doesn’t reduce spontaneously. When being examined your patella will feel unstable as if it might dislocate again. This is called the ‘apprehension test’.