Knee sprains
Knee sprains refer to injuries in any of the ligaments of the knee. The most commonly injured are medial collateral ligament (MCL) running along the inner side of the knee, lateral collateral ligament (LCL) running along the outer side of the knee and anterior cruciate ligament (ACL) that connects the femur and tibia inside the joint (Fig. 1). For more about knee joint anatomy click here.
Fig. 1: Common types of knee sprain. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Commonly, injury happens after a direct blow to the knee. When the knee is hit from outside it moves inwards and the ligament on the inside (the MCL) is overstretched and injured. Inversely, when the blow comes from the inside of the knee it’s the outside ligament (the LCL) that is hurt. ACL injuries, on the other hand, are caused by twisting movement of the knee and are most common among athletes in sports that involve sudden rotation movement of lower leg.
Fig. 2: Completely torn ACL. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
Mild sprains (stretched ligament but no tear or small tears) can be treated with rest, knee exercises and physical therapy. Complete tears require surgical repair or reconstruction.
ACL reconstruction surgery
Below is a narrated animation of ACL reconstruction surgery. Click here to license this video and/or other orthopedic videos on Alila Medical Media website.
This procedure is used to replace a severely damaged or completely torn anterior cruciate ligament (ACL) with a graft. The graft is a piece of healthy ligament taken from the same person or a donor. Graft from the same person is called autograft and usually works best. The procedure is detailed in Fig. 3. Autograft is commonly taken from the patellar ligament (one that connects the kneecap to the tibia), but hamstring tendon may also be used. See the figure legends for details of procedure, step 1 is done through open surgery, the rest are done through an arthroscope.
Fig. 3: Steps of arthroscopic knee surgery for reconstruction of anterior cruciate ligament injury: 1. Graft taken from kneecap and patellar ligament; 2. Torn ACL shown; 3. Damaged ACL removed and a channel is drilled through tibia and femur; 4. graft inserted and secured with screws; 5. graft in place. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.
