MENISCAL KNEE INJURIES. Acute meniscal (or semilunar cartilage) injuries are common. The majority will settle with conservative treatment.

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1 MENISCAL KNEE INJURIES Introduction Acute meniscal (or semilunar cartilage) injuries are common. The majority will settle with conservative treatment. The most immediate complication will be a locked knee due to a detached or displaced meniscal segment. Anatomy Head of right tibia seen from above, showing menisci and attachments of ligaments, (Gray s Anatomy, 1918) Structural attachments in the midline from anterior to posterior, ( my aunt Laura loves MPs ) include: Medial meniscus, anterior horn attachment Anterior cruciate ligament

2 Lateral meniscus, anterior horn attachment Lateral meniscus, posterior horn attachment Medial meniscus, posterior horn attachment Posterior cruciate ligament. The menisci consist of fibro-cartilage. Both are C shaped in plan and triangular in cross section with the thicker section peripherally placed and the thinner section directed medially. They rest on the tibial condyles. The upper surfaces of the menisci are concave, and in contact with the condyles of the femur; their lower surfaces are flat, and rest upon the head of the tibia. Medial meniscus: The medial meniscus is larger and more semi-circular in shape. The medial meniscus is relatively more attached than the lateral meniscus. It is attached to the capsule and medial collateral ligament. Lateral meniscus: The lateral meniscus is smaller and more circular in shape. The lateral ligament is separated from the lateral collateral ligament by the popliteus muscle. The lateral meniscus is therefore relatively less attached than the medial meniscus and is actually pulled backwards at the beginning of knee flexion. Functions of the menisci: Add structural stability (along with the ligaments and surrounding muscles) to the knee joint. The cross sectional area deepens the articulation laterally for the femur on the tibia. Acts as shock absorbers by reducing and spreading the load transmitted from the femur to the articular cartilage of the tibia. Helps control the complex functional gliding and rolling actions of the knee joint. Mechanism of Injury Meniscal injuries are more common in males. Medial meniscal injuries are more common than lateral meniscal injuries, because: 1

3 The medial compartment of the knee carries about 90% of weight bearing of the knee joint It is much less mobile than the lateral meniscus. In young people meniscal injuries are usually the result of a forceful twisting movement whilst the knee is flexed and weight bearing In older age groups meniscal injury may be due to degenerative changes predisposing to damage from more minor injuries Classification of meniscal tears: I II III IV V The majority of tears commence as vertical (or longitudinal) splits (I). When the free edge is significantly displaced (II) it is known as a bucket-handle tear. When the displaced split is confined within the anterior horn (III) or posterior horn it is known as a racket tear. The central edge may rupture forming a parrot-beak tear (IV). In middle age horizontal tears may occur (V) within the substance of the meniscus, sometimes without obvious trauma. 2 Complications 1. Immediate: 2. Late: Locked knee Secondary degenerative changes with chronic pain

4 Impaired knee joint function. Clinical Features Symptoms: 1. Pain is exacerbated by weight bearing. 2. Typical features of a detached or semi-detached intra-articular fragment include: Signs: Clicking sensation. Sudden giving way of the knee. Locking of the knee. Here the knee is not able to be fully extended and there is a restricted range of movement. 1. Pain and tenderness is localized to the medial or lateral joint line. 2. Swelling may be seen, but may also be minimal. 3. McMurray s test: This is the classic test for a torn meniscus. It is based on the fact that a loose segment can sometimes be trapped between the articular surfaces and then induced to snap free with a palpable or audible click or pain. The patient lies supine The knee is flexed as far as possible. Palpate the medial joint line, whilst the foot is everted. The knee is then extended. A medial meniscal injury is indicated if there is an audible or palpable click or significant pain. After the knee is flexed again palpate the lateral joint line, whilst the foot is inverted. A lateral meniscal injury is indicated if there is an audible or palpable click or significant pain. 4. Apley s grinding test: The patient lies prone The knee is flexed to 90 degrees.

5 A compression force is applied to the foot. The foot is rotated internally and externally Pain is experienced if there is a meniscal injury. Also: The foot may then be rotated internally and externally with a distraction force applied, whilst keeping the thigh on the bed (thus taking pressure off the meniscus). If there is pain on rotation this tends to indicate a ligamentous injury (as opposed to a meniscal one). 5. Quadriceps wasting: Investigation This may be a feature of longer term chronic injury. Plain radiography: Plain x-rays do not directly assist in assessing meniscal injuries of the knee, however they should still be done in cases of acute injury to rule out other nonmeniscal injuries, such as unsuspected tibial plateau fracture or patella fracture. MRI: This is the best imaging investigation, short of arthroscopy. It can preclude the need for arthroscopy in many cases. Arthroscopy: This is the gold standard investigation for the assessment of meniscal knee injuries and also allows for some therapeutic interventions. It is however invasive and requires a general anaesthetic and so symptoms should be of enough significance to warrant the procedure. Management 1. Initial management will be RICE, (rest, ice, compress and elevate) as for any soft tissue injury. 2. Locked knee:

6 This will be most immediate complication. Many will unlock spontaneously over hours Gentle manipulation with appropriate analgesia may be attempted in the ED. Flexion/ extension and internal/ external rotation movements may be tried. If unsuccessful refer to the orthopedics unit. EUA or even arthroscopy may be required. 3. Conservative management: If the knee is not locked, most injuries can be managed conservatively at least in the first instance. Arrange for: Analgesia, (NSAIDS are best if there are no contra-indications to these.) Physiotherapy assessment in the ED or referral to physiotherapy if the ED physiotherapist is not available. Tubigrip Crutches Referral to sports injury clinic. If conservative measures fail, then an orthopaedic opinion will be required regarding the need for an MRI and/ or an arthroscopy. 4. Orthopaedic referral for possible admission from the ED: This will be needed for patients with severe symptoms and/ or significant functional disability such as locked knee.

7 References 1. Meniscal Lesions in Apply s System of Orthopaedics and Fractures 7 th ed Meniscal Injuries in McRae R. Practical Fracture Treatment. 3 rd ed 1994 Dr J. Hayes October 2007