Your knees are complicated joints that move a bit like door hinges. Each joint contains three bones, your thigh bone (femur), shinbone (tibia) and kneecap (patella). The ends of the femur and tibia, as well as the back surface of the patella, are covered in smooth, slippery cartilage to allow for smooth movements. Four ligaments hold these bones together to stabilise your knee joint, while tendons connect them to your muscles to allow movement. Any of these tissues can be injured while playing sports.
Any of the bones in your knee joint — the patella, femur or tibia — can be fractured from a fall or direct impact. If the bone breaks in such a way that one part is displaced relative to the other or if the break involves the joint surface, surgery is needed to stabilise the bone.
The most common ligament damaged in the knee is the anterior cruciate ligament (ACL). However, the three other ligaments in your knee — posterior cruciate ligament, medial collateral ligament and lateral collateral ligament — can also be injured.
Ligament injuries are classified into three grades. Grade 1 refers to a sprain, where the ligament is overstretched but not torn. Grade 2 is a partial tear and grade 3 is a complete tear of the ligament.
The ACL is usually injured while pivoting (ie when the foot is stationary and you twist or turn it) or suddenly stopping. These injuries often occur when playing sports such as football or netball.
A complete tear of the ACL will cause instability in your knee when pivoting. However, as the ACL isn’t necessarily needed for movements in day-to-day life, surgery isn’t always needed.
If you want to continue playing sports that involve pivoting, reconstructive surgery is usually the preferred option. However, if this isn’t the case, physiotherapy to rehabilitate your knee may be sufficient, followed by avoiding physical activities that don’t involve pivoting and switching to others, such as running in a straight line or swimming.
Surgical reconstruction of the ACL usually involves grafting tendons from elsewhere onto the damaged ligament, such as a hamstring tendon, patellar tendon or quadriceps tendon. This is a minimally invasive procedure as it is performed as a keyhole surgery. You can usually return home on the same day as your surgery or the day after.
The initial phase of your recovery will take several weeks and you will need to perform daily rehabilitation exercises to restore movement and strengthen your knee. Depending on the progress of your recovery, it will take at least six to nine months before you can return to sports that involve pivoting.
A collateral knee ligament sprain is usually treated with rest, applying ice packs and performing exercises to restore range of movement. However, if one of your collateral ligaments is completely torn, you will need to wear a brace to support and stabilise your knee while it heals, or alternatively, you will need surgical reconstruction.
Isolated tears to the posterior cruciate ligament can usually be effectively treated with physiotherapy to rehabilitate your knee and improve balance. However, if you are having symptoms of instability, you may need surgical reconstruction.
Sitting on top of your tibia inside your knee joint are two C-shaped pieces of cartilage called menisci. They act as shock absorbers and are usually injured during twisting motions, or in older people, due to degeneration over the years that causes the menisci to become less elastic. The result is a meniscus tear, which can be felt as a pop and with large tears, can cause your knee to become stuck or locked.
Small meniscus tears often heal on their own with rest. However, larger tears can cause problems in the movement of your knee and need keyhole surgery.
Surgery to repair a meniscus tear focuses on preserving the meniscus as much as possible. Tears can occur in either of two zones of the meniscus — the red zone, which is the outer third of the meniscus and has some blood supply, and the white zone, which is the remaining inner two thirds of the meniscus and has little to no blood supply. Red zone tears can be repaired with surgery, while white zone tears usually can’t be repaired and instead the torn, unstable portion of the meniscus is trimmed off to prevent it catching between the bones of the knee joint.
Meniscus tears caused by degeneration don’t usually need surgery but can take two to six months to heal on their own. If you continue to have mechanical problems after this time, your doctor may suggest you have a type of keyhole surgery called an arthroscopy, where the damage can be investigated and if needed, repaired.
As with ligaments, tendons in the knee can also be torn. In younger people, the most common knee tendon injury is a patellar tendon tear, while in older people, it is more likely to be a quadriceps tendon tear. Partial tendon tears can be treated with rest and wearing a brace. Complete tears always need surgery to repair the torn tendon.
Dislocation occurs when a bone slips out of place and in the knee, particularly in younger people, this most commonly occurs with the patella. In most cases, this is due to a biomechanical abnormality eg when the patella sits too high, the groove of the femur in which the patella sits is too shallow or there is a muscle imbalance. Any of these biomechanical problems can cause recurrent patellar dislocations. Surgery is needed to prevent further dislocations.
Less commonly, the tibiofemoral joint can become dislocated ie the joint connecting the tibia to the femur. This most often occurs due to a major impact and can cause damage to nerves and blood vessels around the knee — this is a surgical emergency. An MRI scan will usually be needed to assess the damage to ligaments before surgery to reconstruct them.
Mr Ahmad Mobeen Ismail is a Consultant Orthopaedic Surgeon at Spire Manchester Hospital, specialising in sports injuries, knee injuries, knee arthroscopy, hip and knee arthritis, and hip and knee replacement. He has further advanced his expertise by visiting centres of excellence in orthopaedic surgery in the US and Europe to learn new techniques. His current interests lie in promoting short-stay hip and knee replacements via minimally-invasive surgery and new techniques for pain control and rehabilitation.