#treatment - Knee
- The most commonly torn ligament inside the knee is the anterior cruciate ligament (ACL)
- The ACL normally stops the top of the shin bone from slipping forwards
- An ACL rupture can lead to knee instability causing the knee to feel wobbly and give way
- ACL rupture can be treated with physiotherapy to compensate for the missing ligament by strengthening the muscles that support the knee
- Patients with continuing instability should have the ligament surgically reconstructed
- After ACL reconstruction intensive physiotherapist supervised rehabilitation is essential
- The results of ACL reconstruction are excellent, with up to 90% of patients returning to full or nearly full sporting activities
Unfortunately, when the ACL tears it is like a bungee rope snapping, and the ends of the ligament ‘ping’ apart. It is impossible to simply stitch the torn ends of the ligament together, and reconstruction with a ligament graft is required.
Occasionally (normally in children and adolescents) the ligament may pull a chunk of bone off the tibia (an ACL avulsion fracture). In this situation it may be possible to repair the ligament damage by fixing the bone fragment back in place, with the ligament still attached to it.
In the large majority of cases, surgical treatment of an ACL rupture involves:
- The procedure is carried out under general anaesthetic
- The knee is examined arthroscopically to assess concomitant injuries
- A ligament graft is obtained by harvesting a section of either the hamstring tendons of the same knee (the gracilis and semitendinosus tendons) or else a portion of the patellar tendon (with small bone blocks at either end).
- Tunnels are drilled through the bones of the tibia and the femur into the knee joint.
- The tendon graft is threaded through into the knee, and the ends are fixed firmly using either screws or other specialised fixation devices which hold the graft in place under tension.
- Patients are normally able to be discharged the day after their surgery.
Post-operative rehab is an absolutely key part of the overall treatment of an ACL rupture. Surgical reconstruction without appropriate rehabilitation is probably a pointless exercise.
Patients may require one crutch post-operatively, just for a few days, until the pain from the procedure begins to settle. However, knee braces are not required and the graft strength and fixation should be firm immediately post-operatively.
Rehab regimes may vary considerably depending on whether other concomitant procedures are carried out at the same time as the ACL reconstruction. However, the basic standard ACL rehab regime involves:
- Day 1 – Week 6: Full weight bearing ASAP. Range of motion treatment. Muscle strengthening. Training of the reflexes (proprioception). Closed chain exercises only, ie the foot remains in contact with something (such as the floor), so that there is no hopping, skipping, jumping or running.
- Week 6 – Week 12: Commencement of open chain exercises (where the foot can leave the floor) eg running, but no sport
- Up to 9 months: Intensive focussing on muscle strengthening, proprioception and performance of sport-specific training exercises
- From 9 months: Careful return to competitive sport
When tendon tissue is first harvested for a graft, as soon as the tissue is harvested it loses its blood supply. The cells within the tissue, responsible for constantly repairing the fibres of the tissue, thus die and the graft becomes little more than a biological scaffold, in which the fibres will begin to degrade and gradually rupture with time, thereby weakening the tissue.
When the graft tissue is inserted into the knee, it begins to grow a new blood supply. New cells migrate into the tissue and begin to repair and remodel the graft. Therefore, an ACL graft is nice and strong when it is first surgically implanted. However, initially the knee is weak and the reflexes impaired. As knee function improves and the patient’s confidence increases, the graft begins to degenerate and actually becomes weaker. The ‘danger zone’ is between 3 to 9 months. As the graft develops a new blood supply within the knee after surgical reconstruction, the new cells remodel the graft and it becomes stronger. By 9 months, the graft will look and function like a new ligament and should be strong enough to cope with a full return to sports.
Graph showing how the strength of the ACL graft initially drops and then gradually returns to normal as the graft grows a new blood supply and slowly remodels. The graft is at its weakest at 3 to 6 months – just when the patient is beginning to regain confidence. It is therefore essential that return to proper sport is delayed until 9 months post-op.