The anterior cruciate ligament (ACL) is one of the two strong cords that stabilise the interior of the knee. The ACL stops the tibia moving forwards on the femur and also preventing some twisting movements of the knee. Injury classically happens when the knee is twisted suddenly when changing direction.

Symptoms and Signs

People will classically mention that the foot was fixed on the floor / landed awkwardly and then felt a pop or snap in the knee. This is often accompanied with large rapid swelling to the knee and an inability to continue the activity they are playing. Given time the swelling and pain will settle and the knee may continue to misbehave when changing direction. If the knee gives way then the knee may suffer a further irrecoverable injury – hence the need for early diagnosis and advice.


The acute pain and swelling of the knee should be managed according to the P.R.I.C.E regime (link to first aid section). Once the knee has recovered from this painful phase then there are two options available that may suit one patient more than the other.

Non-operative Rehabilitation

If the patient participates in activities that don’t involve the need to rapidly twist their knee then they may be rehabilitated with our physiotherapy team and return to activity. Sports involving running in straight lines, swimming or cycling may thus wish to not have surgery. Unfortunately there does remain a risk of the knee giving way in planned or unplanned activity that may cause further knee injury.


Once the ACL is torn at present current evidence does not suggest it can be repaired (hopefully research can answer this question soon) and so it needs to be replaced or reconstructed with a ‘graft’. The majority of grafts come from either the hamstring tendons (semi-tendinosus and gracilis) or the knee cap tendon (patella tendon) but can also some from the quadriceps tendon. The graft is placed into the knee using keyhole surgery techniques. The graft takes 9 months to incorporate and become strong enough to return to sport. Physiotherapy will take place during this period of time and concentrate not just movement and strength but also balance / feedback and activity specific rehabilitation with injury prevention.

Posterior Cruciate Ligament


The posterior cruciate ligament (PCL) is the largest ligament inside the knee. It is also helped by two smaller variable meniscofemoral ligaments that are about 1/5th the size of the PCL. The PCL is injured much less frequently than the ACL. Would you like to know more / click for more… The PCL stops your tibia from moving backwards on your femur. The classic mechanism is when your tibia is thrust forcibly backward such as a direct blow on the front of your tibia near the knee joint. Injury to the PCL can be accompanied by injury to another supporting ligament of the knee. Goalkeepers are an example of a sport position with a high risk for PCL injury.

Symptoms and signs

The knee pain may well be much milder than one would expect. This is because most internal knee injuries cause your knee to swell up impressively with blood. If this balloon (capsule) around your knee joint bursts, as frequently occurs with PCL injury, then the blood leaks out taking the pressure and therefore the pain off the knee. The blood that has escaped from your knee joint forms bruising that may be seen in and around your knee but may also go into the calf / thigh and heel areas. Bruising around your knee after an injury can be indicative of a significant disruption to your knee and we would recommend you make urgent clinic appointment.

Patients with chronic problems to the PCL may complain of vague symptoms of instability (but not as bad as ACL injuries), pain on the front of their knee and medial knee (due to the new ‘tracking’ of their knee without a PCL). People who participate in ‘explosive’ sports requiring rapid acceleration and deceleration may notice a lack of control.


The acute pain and swelling of the knee should be managed according to the P.R.I.C.E regime (link to first aid section). Important to get an urgent referral and appointment because the PCL has a good blood supply and so has potential to heal if diagnosed early.

Non-operative rehabilitation

Early splinting or bracing of the PCL injury may well mean that the PCL heals to give good functional stability. Isolated PCL injuries will tend to be splinted initially and reassessed frequently in the brace with ongoing specialist physiotherapy rehabilitation. Similarly the use of a brace in a chronic PCL injury may help to identify patients who may benefit from surgical treatment. The vast majority of patients with an acute PCL injury are managed in a brace for several months.

Operative treatment

The PCL needs to be replaced with a graft. The tissue used for this large ligament tends to be either from the patients’ own hamstrings or from donor Achilles tendon tissue to produce a very strong graft. The graft needs protection after it has been fixed into the knee and will need a specialist support brace to be worn for at least 4 months. Surgery may be advocated early in professional athletes and in a knee that has been severely injured and needs several ligaments rebuilding.