Meniscal tears are a common form of knee injury. They involve damage to the meniscus, which is cartilage in the knee joint. It is sometimes described to patients as damage to the cartilage.
Basic Knee Anatomy
The knee is a hinge joint. Between the femur and the tibia are the menisci. There is a medial and lateral meniscus. The rounded bones at the end of the femur (condyles) do not match the slightly convex areas (also called condyles) at the top of the tibia. Therefore, the menisci help the femur and tibia fit together and move smoothly across each other. They act as a shock absorber, distribute weight throughout the joint and help stabilise the joint.
Also in the knee is a joint between the anterior femur and the patella (patellofemoral joint). The patella sits in a groove on the femur called the trochlea (or patellofemoral groove). The quadriceps tendon attaches to the patella, which is attached to the tibia by the patellar ligament. Contraction of the quadriceps muscles causes knee extension by pulling through the patella.
There are four ligaments in the knee:
- Anterior cruciate ligament
- Posterior cruciate ligament
- Lateral collateral ligament
- Medial collateral ligament
Meniscal tears often occur during twisting movements in the knee. In young patients, this often happens when playing sports.
With increasing age, the meniscus becomes more prone to injury. Tears can occur with minor twisting movements in older patients (e.g., standing from seated with an awkward twist in the knee).
The initial injury can be accompanied by a “pop” sound or sensation.
- Restricted range of motion
- Locking of the knee
- Instability or the knee “giving way”
Pain may be referred to the hip or lower back.
Examination findings are:
- Localised tenderness on the joint line
- Restricted range of motion
Traditionally, the two key special tests for meniscal tears are McMurray’s test and Apley grind test. These are generally not used or recommended in clinical practice as they can cause pain and may worsen the meniscal injury.
McMurray’s test involves the patient lying supine. The examiner takes the leg and flexes the knee.
While internally rotating the tibia (by turning the foot inwards) and applying varus pressure to the knee (applying outward pressure to the inside of the knee), carefully extend the knee. Pain or restriction indicates lateral meniscal damage.
Repeating the flexed to extended movement with external rotation of the tibia and valgus (inward) pressure on the knee tests for medial meniscal damage.
Apley Grind Test
The Apley grind test involves the patient lying prone and flexing the knee to 90 degrees with the thigh flat on the couch. Downward pressure is applied through the leg into the knee, and the tibia is internally and externally rotated at the same time. Pain indicates a positive result, suggesting meniscal damage. The pain is localised to the area of damage (e.g., medial or lateral meniscus).
Ottawa Knee Rules
Bone fractures are worth considering as a differential diagnosis in patients presenting with acute knee injuries. The Ottawa knee rules can be used to determine whether a patient requires an x-ray of the knee after an acute knee injury to look for a fracture.
The Ottawa knee rules state that a patient requires a knee x-ray if any of the following are present:
- Age 55 or above
- Patella tenderness (with no tenderness elsewhere)
- Fibular head tenderness
- Cannot flex the knee to 90 degrees
- Cannot weight bear (cannot take 4 steps – limping steps still count)
MRI scan is usually the first-line imaging investigation for establishing the diagnosis.
Arthroscopy can be used to visualise the meniscus within the joint and is the gold-standard investigation for diagnosing a meniscal tear. Arthroscopy can also be used to repair or remove damaged sections of the meniscus.
The NICE clinical knowledge summaries on knee pain (updated 2017) recommend urgent referral in patients with an acute onset of knee pain associated with symptoms suggestive of an acute meniscal tear. Local pathways vary, and this may involve sending the patient to A&E or the fracture clinic. Key symptoms include:
- A “pop”
- Rapid onset swelling
- Instability or giving way
Conservative management of most acute soft tissue injuries, including meniscal tears, is with the RICE mnemonic:
- R – Rest
- I – Ice
- C – Compression
- E – Elevation
NSAIDs are usually used first-line for analgesia in MSK injuries.
Physiotherapy can be used for rehabilitation after the initial pain and swelling have settled.
Surgery may be required. This involves arthroscopy (keyhole surgery) of the knee joint. The main options are:
- Repair of the meniscus if possible
- Resection of the affected portion of the meniscus (this often results in osteoarthritis)
Last updated August 2021