PCL injury (posterior cruciate ligament): symptoms, grades and recovery

The knee is held together by four main ligaments. The posterior cruciate ligament runs inside the joint. Royal Cornwall Hospitals NHS Trust describes it as one of the ligaments in the knee that keeps the joint stable.

The trust says a PCL injury might happen during direct contact while playing sports, for example to the shin when falling on a bent knee, by twisting the knee, or when the knees hit the dashboard in a car accident. The trust also notes that other areas inside the knee, such as cartilage, may be damaged, so the whole knee is assessed.

The NHS describes a sprain as a torn or twisted ligament and notes that sprains are most common in the wrists, ankles, thumbs and knees. A PCL injury is a sprain or tear of this kind, with the severity described by the grade.

The Royal Cornwall trust grades soft tissue knee injuries by severity, and the grade influences treatment.

The trust says that you may have a few symptoms or none, and you may be able to walk normally. You might have some pain and mild swelling. If the injury is not treated you may feel more generalised knee pain and discomfort when running, walking distances and going down stairs.

The trust notes that swelling is normal after injury and is often worse at the end of the day, which is why elevation matters in the first days.

• Pain and mild swelling in the knee after a knock or fall.

• Generalised knee pain that builds over time if the injury is not managed.

• Discomfort when running, walking distances or going downstairs.

• A feeling of instability if the ligament is completely torn.

The NHS says to get advice from NHS 111 now if your knee is very painful, you cannot move it or put weight on it, it is badly swollen or has changed shape, it locks, gives way or painfully clicks, or you have a very high temperature with redness or heat around the knee. For an injury that is very painful or getting worse, the NHS sprains page also lists a large amount of swelling or bruising, being unable to put weight on it or walk more than a few steps, and no improvement after treating it yourself.

If you have had an injury to the knee in sport or an accident and you suspect a ligament injury, a fracture clinic, urgent treatment centre or minor injuries unit can assess it, and the NHS says in many areas you can refer yourself to community musculoskeletal services for physiotherapy without a GP referral.

The Royal Cornwall leaflet describes the PRICER approach for the first 72 hours: protect, rest, ice, compression, elevation and rehabilitation. It advises resting the leg, elevating it above hip level, applying a cold pack regularly and using crutches or a support bandage. Ice packs or a bag of frozen peas wrapped in a wet thin towel can be used for up to 15 minutes every few hours, never directly on the skin and not for more than 20 minutes at a time in one hour.

The NHS adds that after 2 weeks most sprains and strains feel better and that strenuous exercise such as running should be avoided for up to 8 weeks to reduce the risk of further damage, with severe injuries taking months. A pharmacist can suggest painkillers such as paracetamol and ibuprofen gel.

For mild injuries, PRICER plus time allows healing, the trust says, while more severe injuries may need imaging such as an MRI scan. It describes the aims of treatment as managing pain, minimising swelling, maintaining range of movement, keeping the quadriceps working and stopping the hamstrings from taking over too much.

Physiotherapy is an integral part of managing knee injuries, whether or not an operation is planned. The trust's care plan includes static quadriceps exercises, inner range quadriceps exercises, knee bending and straightening within the brace, straight leg raises and mini squats, done several times a day as guided by pain and swelling.

The trust's leaflet describes a PCL brace worn for 12 to 16 weeks, kept on at all times except for washing, with exercises done in the brace for at least 6 weeks. This reflects one NHS trust's protocol, so follow the plan you are given. It says the injury may heal on its own over time with the brace, and that an operation may be needed if the knee remains unstable once the brace is removed.

If surgery is an option, the trust says a knee surgeon will discuss the risks and benefits so you can make an informed decision, and exercises before the operation (prehabilitation) help you prepare for and recover from it. For comparison, the NHS describes ligament reconstruction in the ACL as replacing the ligament with a graft, with physiotherapy afterwards and a recovery that usually takes several months or more.

While the leg is braced and you are moving less, the trust says you are at higher risk of a blood clot (deep vein thrombosis). Symptoms to watch for are throbbing or cramping pain in one leg, usually in the calf or thigh, swelling in one leg, warm skin and red or darkened skin around the painful area, and swollen veins that are hard or sore to touch. Seek urgent medical advice if these appear.