ACL injury: symptoms, treatment and recovery

A knee surgeon at Leeds Teaching Hospitals NHS Trust describes the typical story. A significant force goes through the joint and it feels like a pop in the knee. The knee swells up soon after, and people often limp for a few days to two weeks. It can occur with contact from someone else or when you twist without any contact.

Leeds Teaching Hospitals NHS Trust says an injury can result in the knee giving way. The NHS lists a knee that is unstable, gives way when you try to stand, is unable to straighten, or where you may hear a popping sound during the injury, as a pattern that can mean a torn ligament, tendon or meniscus, or cartilage damage.

The Leeds surgeon says that if you have injured your knee and it is significantly swollen and you are struggling to work, you should seek medical attention from a GP or an urgent service, which can direct you to the appropriate pathway.

The anterior cruciate ligament is one of the main ligaments inside the knee. Leeds Teaching Hospitals NHS Trust says it provides the knee with stability, and the Leeds surgeon explains that it keeps the knee together, especially in twisting movements.

It is a common injury, usually occurring in sports that involve pivoting or twisting. The surgeon notes that clinicians also assess the structures around the knee, such as other ligaments, because damage to them influences management.

The Leeds surgeon says it is usually caused while doing sports which involve mostly pivoting or twisting, and can happen from a contact injury with someone or a twist without contact. The NHS notes that pain after overstretching, overusing or twisting, often during exercise, can be a sprain or strain, while an unstable knee that gives way, cannot straighten or made a popping sound at injury can be a torn ligament, tendon or meniscus.

Leeds Teaching Hospitals NHS Trust says your clinician will examine the knee. The Leeds surgeon says that good clinical assessment can often identify an injury to the ligament, and that the doctor may ask for imaging, either X-rays or an MRI scan, to see whether other structures besides the ACL have been damaged, because that can influence management.

NICE Clinical Knowledge Summaries (CKS) on knee pain says that if there is a history of trauma, an assessment for fracture, tendon rupture and ligament tears is required, along with a neurovascular assessment. It recommends immediate referral for severe pain, swelling, instability or inability to bear weight in association with an acute injury.

Most hospitals have an acute knee service where these injuries can be assessed, says the Leeds surgeon.

Treatment depends on what you need your knee to do and on damage to other structures. The Leeds surgeon says options are surgery or a trial of physiotherapy. Some people can manage without a reconstruction, especially if their sport mostly involves running in a straight line, and may be given the option of trying physiotherapy first. If there are other injuries to the knee, a surgeon may sometimes advise surgery directly.

The Leeds physiotherapists emphasise the period between injury and any surgery. Early on, swelling is managed by elevating the knee, using ice if allowed and starting very gentle exercises. As movement improves, early strengthening follows. They say there is a successful conservative path that people can take without surgery and get excellent outcomes if they do the correct exercise and manage things well. Equalising the strength in the two legs is a key aim, with early work on straightening the knee.

If surgery is chosen, the Leeds leaflet says a reconstruction involves removing the torn ends and replacing the ligament with a graft, usually taken through a small incision from the hamstring tendons. Keyhole incisions are used to make tunnels in the shin bone and thigh bone, and the graft is secured with buttons and/or screws. If meniscal or cartilage surgery is needed it can usually be done at the same time. The leaflet says surgery is best done once you have recovered your full movement, which is why prehabilitation matters: the stronger and more functional the knee before surgery, the better the outcomes after it.

The Leeds leaflet says rehabilitation after reconstruction requires dedication, and the process can take up to 1 year to complete successfully, and may be delayed if complications arise or rehabilitation is not followed. You are usually discharged after physiotherapy review and when pain is under control, and crutches are generally required for up to three weeks.

The leaflet describes three stages: an early stage with one-to-one physiotherapy for pain, swelling and range of movement; a mid stage with classes to build strength, mobility, stability and some dynamic tasks such as running; and an advanced return-to-sport stage with vigorous strengthening and a gradual introduction of hopping, jumping, sprinting, cutting and pivoting drills. Evidence-based criteria must be met before returning to sport.

The leaflet lists the risks of surgery, including infection, stiffness, swelling, scarring, pain, graft re-rupture, nerve injury and sensory loss, loss of muscle strength and bruising. It says the risk of deep vein thrombosis is very low.

Not every knee injury is an ACL tear. The NHS says knee pain can be a symptom of many conditions and that you should not self-diagnose.

The NHS says to get advice from NHS 111 now if any of the following apply. 111 will tell you what to do and where to go, and you can also go to an urgent treatment centre.

• Your knee is very painful.

• You cannot move your knee or put any weight on it.

• Your knee is badly swollen or has changed shape.

• Your knee locks, gives way or painfully clicks (painless clicking is normal).

• You have a very high temperature, or feel hot, cold or shivery, with redness or heat around the knee, which can be a sign of infection.

The NHS says knee pain that does not improve within a few weeks should be seen by a GP, and that in many areas you can refer yourself to a community musculoskeletal (MSK) service for physiotherapy without a GP referral. Many hospitals have an acute knee service for significant injuries.

Some people choose a private knee surgeon or physiotherapist, particularly for an MRI scan or to speed up a decision about surgery. In general terms the same options and rehabilitation apply, so it is worth asking who will provide the structured physiotherapy before and after any operation, and what the criteria are for returning to sport.