The knee is stabilized by 4 main ligaments. The 2 central ligaments are in the form of a cross and are called the cruciate ligaments. The ligament in front that stabilizes the knee from slipping to the front is called the anterior cruciate ligament or ACL. The one at the back of the knee that stabilizes the knee from slipping backwards is the posterior cruciate ligament or PCL. Injury to these ligaments can involve either in stretching, partial tears of 1 of 2 bundles of the ligament, complete tear of the tendon either in the centre or either end near its attachment to the thigh bone (femoral attachment) or to the leg bone (tibial attachment). The ligament may also sometimes pull off with a spike of bone. It is one of the most common causes of knee pain and instability in young or middle-aged adults more so those involved in contact sports.
Causes
ACL tears result from a posteriorly directed impact force onto the front of the knee over the leg bone. It may occur while playing sports such as football, soccer, basketball and volleyball or during motor accidents. Tears of the ACL can also occur from a fall, knee dislocation or heavy lifting. Rarely deposits of calcium or uric acid on the ACL can also predispose to tears.
Symptoms
ACL tears often cause severe pain, swelling, instability and weakness of the knee, and crackling sensation on moving the knee in certain positions. There may be stiffness, swelling, loss of movements, and tenderness in the front of the knee. If you have an ACL tear you may find climbing stairs difficult or even difficulty when running or making sharp turns when playing active sport
Diagnosis
An ACL insufficiency / tear diagnosis is based on the physical examination, X-rays, and imaging studies, such as MRI. ACL tears are best viewed on magnetic resonance imaging (MRI). A tear involving less than 50% of thickness or one that is not causing instability may be treated conservatively. A tear greater than 50% of the thickness causing disability with work or activities of daily living may need surgery. The tears cannot be repaired as the ligament has no intrinsic blood supply. In old tears where early arthritis has set in due to old tears, an MRI scan and weight bearing comparative knee Xrays may be required to assess the degree of arthritis.
Conservative Treatment Options
- Rest
- Knee brace
- Non-steroidal anti-inflammatory medication
- Certain exercises to help strengthen the muscles of the knee
- In rare instances Dr Bala may opt to use cells from your own blood that are rich in undifferentiated cells. This preparation is called Platelet Rich Plasma or PRP. This injection may aid healing of minor tears of the ACL.
Surgery
ACL reconstruction may be performed by either an open surgery or arthroscopic procedure. But almost always nowadays through the arthroscopic (keyhole) procedure. There are many graft options but the commonest graft used will be of the 2 tendons from the inner side of the knee (hamstring tendons) to replace the old torn ACL. In instances where a previous ACL surgery has failed a PTB graft (tendon of the front of the knee with a piece of bone on either side) can be used to reconstruct the ACL. Other sources of graft in revision scenarios will be from the tendon in the front of the knee (quadriceps graft) or tendon from the outer ankle (peroneus longus graft). The graft tendons are prepared to atleast 8 mm diameter and 120 mm in length.
The first step in ACL reconstruction, is to inspect the knee through a camera. Associated damage to the cartilage of the knee is addressed (chondroplasty) and inflamed lining of the joint is removed (synovectomy). Then the 2 cartilage washers of the knee (menisci) are inspected and either trimmed or repaired (meniscectomy). Then the space for ACL will be created by indentifying the attachments on the thigh bone and leg bone (debridement and footprint identification) and performing a motchplasty to avoid the new graft from impingining onto the thigh bone. The tunnels for the new ligament are prepared in the thigh bone and leg bone. In adolescents and children special techniques to avoid the growing ends of the long bones are used to perform this surgery.
The prepared graft is then passed through the tunnels. Many different implants are available to fix the new ACL graft including buttons, screws and staples. Dr Bala prefers to use a button at the top called an endobutton and a screw at the bottom which incorporates into the bone. He prefers a device called the tight rope with which the graft maybe adequately tensioned to ensure optimal function, as in his hands, the repair is much more robust and he can start moving your knee straight away without restrictions.
On rare occasions if knee arthritis has set in, Dr Bala may decide in your best interests that along with an ACL reconstruction he may perform an alignment altering surgery involving realigning the leg bone and fixing with a plate.
Following surgery, recovery is slow, a knee brace and crutches maybe required for a week to 10 days and you may be advised to practice motion and strengthening exercises.
Dr Bala specializes in salvage of complications of ACL reconstruction, failed ACL surgery or of neglected ACL tears.