Knee ligament injuries are very common and range from a minor twisting sprain which will get better in a few days to a complete rupture of one of the major ligaments and even knee dislocation which occurs most commonly in road traffic accidents.
What are the main ligaments?
The knee has four major ligaments, one running along the inner side of the knee, one on the outer side and two crossed “cruciate” ligaments in the middle between the two sides of the knee. The anterior cruciate ligament is the commonest major ligament injury in the knee and has reached almost epidemic proportions in football. The typical history of the injury is of a non contact twisting where the player and often other players will hear a pop or a crack. He will be immediately aware that something serious has happened and the player will often say he thought he broke his leg. It will swell within a hour because the anterior cruciate ligament is full of blood vessels and they will bleed into the joint. There is no question of him playing on. It also occurs quite commonly in skiing where the tip of the ski gets caught in the snow leading to a twisting injury. Again the story we hear routinely is that the skier is unable to ski down and has to go down in the “blood wagon”.
Because of the severity of the injury the patients almost invariably goes to hospital within a few days and is reassured by the Accident and Emergency Department that it is no more than a sprain. They are given a big bandage and often sent for some physiotherapy. Overall, of patients attending a specialist sports knee clinic with a complete tear of the anterior cruciate ligament only about one in ten has had the diagnosis made before they get there. This is because the examination of the injured knee is quite difficult and the signs of a torn cruciate ligament are often quite subtle and take considerable experience to pick up.
The anterior cruciate ligament will not heal on its own and although people have tried over many years in many unfortunate patients it is not really possible to repair it or stitch it back. What we have to do in order to reconstruct the anterior cruciate ligament is to replace it with a graft see the ACL page. An artificial ligament is nice and easy to do, but because it is not a biological structure it does tend to fatigue and wear out within five to ten years. A better option is to produce a living ligament and the best graft source of all is part of the patient’s own body. There are a number of options for this, but essentially the choice is between using hamstring tendons from the back of the knee and the patella tendon from the front. These are effectively equivalent. The patella tendon is technically easier to use for the surgeon since it has a chunk of bone on each end which makes it easier to fix in theatre. The hamstrings are a little bit more technically difficult to remove through a rather smaller incision and they are also a bit more difficult to fix onto either side of the knee. The results of the procedures are almost exactly the same, but taking the graft from the front of the knee tends to give a little bit more discomfort while kneeling. For this reason I use the hamstring tendons most frequently.
“Partly Torn” Anterior Cruciate
Just occasionally if the cruciate has been stretched out, but not completely torn, we can tighten it using a new and rather experimental technique on which we recently published our results. This was the first major report of this procedure and the largest in the world literature. In suitable cases our results are extremely good (about three out of four success) and this is a simple day-case keyhole procedure with really little or no down sides. It this is not possible and surgery is required then a full blown reconstruction with a graft is needed.
Does it need an operation?
Whilst in young high demand sportsmen most surgeons now would recommend getting on and doing the reconstruction rather than waiting to see. It is certainly possible for individuals, particularly older sportsmen with relatively low demands in non twisting sports to get by without having any surgery at all. We have no way of predicting which individuals can manage well without a cruciate ligament, but individuals who are not going to give up sport, have high demand and a great degree of laxity are most likely to do badly without surgery. There is no evidence as yet that cruciate reconstruction prevents osteoarthritis occurring in the medium to long term, but certainly allowing the knee to continue to give way is doing damage and will very likely lead to cartilage tears sooner rather than later.
For this reason my advice is if the knee is giving way you should either give up doing the things which you are doing to make it give way or else have a surgeon reconstruct it to allow you to do these things. There is nothing in between and if you continue to do sport and allow the knee to collapse underneath you then you are undoubtedly going to do irreparable damage to your knee.
Does the operation always work?
The operation is absolutely routine and has probably a 90% success rate. There are small down sides and risks, but the tendons we take to reconstruct the cruciate grow back surprisingly well. In fact there are reports of surgeons going back and re-harvesting the grafts after they have filled in with scar tissue to do further surgery elsewhere. You can build up the muscles which are removed to form the graft, but it takes quite a bit of rehabilitation. Again we have a routine protocol for rehabilitation following ACL reconstruction, but it usually involves having two days in hospital followed by fairly intensive physiotherapy decreasing in frequency over a period of six months. You can start jogging by 12 weeks and sometimes a little earlier followed by sports specific training.
Overall it takes about six to twelve weeks for the graft to bed into the tunnel and then another twelve weeks or so to get back to full fitness. Under ideal circumstances in professional sportsmen it is sometimes possible to get back at four to five months, but this is not really recommended and you would be better planning on leaving it eight to nine months or a full season. I also routinely tell patients that they will be better in the second season they get rather than the first after they have re-co-ordinated the muscles around the knee and got their confidence back. It is not just the strength of the muscles around the knee which need rehabilitation, although this is important, it is the co-ordination and balance of the muscles which support the injured ligament as it heals.
The Other Ligaments
Surgery to the other ligaments around the knee is much less common. The medial ligament, the ligament that runs up and down the inner side of the knee is very commonly injured. Incomplete injuries heal very well indeed and it is increasingly recognised that even complete tears of the medial collateral ligament will heal with a careful rehabilitation programme and actually better without an operation than with one. For this reason it is quite uncommon for us to repair the medial ligament, just very occasionally we have to come back later if healing has failed.
It is a similar story with the posterior cruciate ligament. This is injured much less frequently than the anterior cruciate ligament, but perhaps surprisingly it does heal well without surgery to reconstruct it. For this reason the vast majority of even high level sportsmen who have a complete injury of the posterior cruciate ligament do not require a reconstruction and return to high level sports. This is most commonly seen in professional rugby league forwards, but I have also seen several goal keepers, including premiership players, who have complete ruptures of the posterior cruciate ligament and yet have returned to full function without needing an operation to repair or replace it.
The lateral or outer side of the knee is a different story and fresh injuries are better repaired than left to heal naturally. This is because the ligaments on the outer side of the knee are really discrete cord-like structures rather than sheets of tissue and they need putting back and stitching back when nature intended. If this is not done then it is likely that the knee will continue to be loose and unstable and require late reconstructive surgery.
Overall the anterior cruciate ligament is the common injury which gives us most trouble requiring surgery. The medial collateral is rarely operated on, but we have very good operations to reconstruct it if necessary. The posterior cruciate rarely require reconstruction on its own, but more commonly requires reconstruction if it is part of a complex knee problem, in combination with multiple ligament repairs. This is a major procedure with significant risks since the posterior cruciate ligament runs from the back of the tibia to the front of the femur and it runs very close to the major arteries and nerves to the lower leg. It is a very big ligament and for this reason the graft which I use to reconstruct it is usually one from a dead body donor so as not to take too much tissue from the patient themselves.
We also now have good procedures for reconstructing the lateral side of the knee, but this again is an open procedure which leaves a scar along the outer side of the knee rather than a keyhole operation.