The knee joint • Made up of two joints: • Tibiofemoral joint: • Hinge joint • Collateral ligaments • Cruciate ligaments • Menisci • Patellofemoral joint: • Medial retinaculum • Patellar tendon
Anatomy-ligaments • ACL • PCL • MCL • LCL • Popliteal ligaments • Meniscofemoral ligament • Transverse ligament
Movements of the knee • Flexion • Extension • Accessory movements in certain positions can take place with external forces: • Valgus • Varus • External rotation • Internal rotation
Patient walks in c/o knee pain • What is the mechanism of injury? • A planted foot with a valgus force and/ or twisting movement is a serious position of danger for the knee • Was there a noise? • Did the knee swell up immediately? • Is there any bruising? • Was the patient able to play on? • Is the patient able to weightbear? • Is there any clicking/ giving way/ locking now?
Patient walks in c/o knee pain • Acute, chronic or sub-acute? • Does pain increase or decrease with activity? • Patient’s job and leisure activities and any possible contributing factors? • Gait? Limping or normal walking? Able to cope with stairs? • Does the patient have any hip pain? • Any back pain? Leg pain? Could this be an L3 Nerve root compression?
Causes of haemarthrosis • ACL tear • PCL tear • Patella dislocation • Osteochondral fracture • Peripheral tear of the meniscus (more commonly medial) • Hoffa’s syndrome (acute fat pad impingement)
More clinical pearls • There is little effusion with collateral ligament tears • An effusion that develops after a few hours or the next day is a feature of meniscal and chondral injuries • Assume everything with a pop or a snap is an ACL tear • Assume all clicking and locking is meniscal... Especially loss of extension • If the knee locks in extension and flexion is difficult it is likely to be patellofemoral pain • Giving way can be indicative of ACL or meniscal injury, but if this is longstanding with no injury, it may be muscle weakness
Ottawa Knee rules • Age 55> or <18 • Tenderness at head of fibula • Isolated patella tenderness • Inability to flex to 90° • Inability to bear weight both immediately and in the emergency department (4 steps) • High suspicion are: • High speed injuries • Children or adolescents • Clinical suspicion of loose bodies 90% of knee X-rays are normal.
Assessment • Observe active range: ability to squat if appropriate, control through the knee. • Observe position of patella in standing • Passive range of movement in supine: loss of particularly extension will cause long term problems • Palpate the patella for differences from side to side
ACL assessment • Anterior Drawer test: • Knee at 90° flexion, foot kept stable • Tibia drawn anteriorly • Assess for degree of movement and end point • Lachman’s Test • Knee at 15° flexion • Draw tibia forward • Assess for degree of movement and end point
ACL assessment • Pivot Shift Test: • Tibia internally rotated • Knee in full extension • Apply a valgus force • In a knee with ACL deficiency the condyles will sublux. The knee is then flexed, looking for the clunk of a reduction, a positive Pivot shift. Extending the knee again, if the knee clicks, this is a positive ‘jerk test’. • Loss of ROM, especially extension • Lateral joint line tenderness due to lateral joint capsule stretching due to subluxation • Medial joint line tenderness if associated meniscal injury
ACL injury • Relatively common in sport • Over 10 000 ACL reconstructions performed in the USA every year • Generally sports that involve pivoting... Football, netball, rugby, gymnastics, downhill skiing etc. • 2-10 x higher risk in females • Can occur in isolation or with meniscal, articular cartilage and MCL injury
ACL injury • 75% rupture chance if there was a twist, a pop and a click! • Extremely painful, particularly at first • Athletes are initially unable to continue their activity, and further activity is limited by significant haemarthrosis. Very occasionally this can be delayed. • Some athletes ‘try’ to play again when knee has settled and report incidences of acute instability • Examination of the knee when swollen is very difficult. Diagnosis should be based on subjective report, and appropriate referral made. • MRI is the imaging of choice, but X-ray is needed to check for an avulsion fracture (‘Segond’). • 80% of ACL tears have a bone bruise over the lateral femoral condyle.
PCL assessment • Posterior sag: • Both knees flexed to 90° and patient relaxed • Observe tibia position relative to femur • Reverse Lachman’s Test • Lachman’s prone! • Posterior drawer test • Knee at 90°, push tibia posteriorly • Also assess in internal and external rotation • Assess range and quality of end point • X-ray to ensure no bony avulsion • MRI is the gold standard for PCL tear assessment
PCL injury • PCL is a primary restraint to posterior drawer and secondary restraint to external rotation. • Less common than ACL (thicker ligament), usually associated with meniscal and chondral injury as well as lateral meniscus injury. • Usually results from a blow to the anterior tibia with the knee flexed. • Hyperextension may also result in injury to the PCL and posterior capsule. • Pain is poorly defined, posterior pain, sometimes in the calf.
Collaterals • MCL: Valgus force • LCL: Varus force • Test at full extension and also 30° flexion • Grade 1: hurts on testing with no laxity visible • Grade 2: hurts and gaps with laxity but with end point • Grade 3 isn’t that painful on testing, LARGE amount of movement. Feels ‘wobbly’. Frequently associated with ACL injuries, often capsular tearing with this grade, swelling therefore present • Always local tenderness at insertion point
Collateral ligament injury • MCL is a result of a valgus force • LCL tear is less common and due to a high-energy direct varus stress on the knee and often associated with PCL tear • Treatment is generally conservative, although bracing is required for more severe injuries.
Menisci • Pain on palpation of the joint line • Positive McMurray’s test: • The knee is flexed and at various stages of flexion the tibia is internally and externally rotated • Pain and a ‘clunk’ make this test positive • Joint effusion • Pain on squatting (especially if posterior horn is involved) • Restricted ROM • MRI is investigation of choice
Meniscal injury • Generally a twisting injury • Doesn’t have to be a quick injury • Degree of pain associated with an acute injury can vary dramatically. • Sometimes a tearing sensation will be felt • Sometimes pain is of late onset... Up to 24 hours later • Small tears may also occur with minimal trauma in the older athlete as a result of degenerative changes • Surgical indications include: • Inability to continue playing • Locked knee or severe lack of ROM, particularly EOR flexion • Palpable clunk on McMurray’s Test • Associated ACL tear • No change after 3 weeks post-injury
Patella and tendon • Assess the patella in 30° knee flexion, push the patella laterally, if the patient has apprehension, consider a dislocating patella • Pain infrapatella is usually the tendon (or can be bursal) • Fractured patella can occur due to direct trauma or through quadriceps avulsion. • In adolescents consider Osgood Schlatter’s Disease, particularly if a prominent tibial tubercle. This is a growth plate osteochondritis
Articular cartilage damage • Chondral damage can be a major cause of symptoms in the knee • Can be primary or secondary (ligamentous instability... ACL has high incidence of medial & lateral femoral condyle and tibial plateau chondral damage)
Anterior knee pain • 20-40% of all MSK consultations in general practice • Generally AKP is due to: • Patellofemoral pain • Patella tendinopathy • Other causes can include: • Synovial plica • Pre-patella/ infrapatella bursitis • Fat pad impingement • Quadriceps tendinopathy • Patellofemoral instability
Patellofemoral pain • Generally insidious onset, vague pain • Often secondary to an acute incidence • A diffuse ache exacerbated by loading eg stairs or running... Doesnt tend to have to be eccentric loading only. • Prolonged sitting can be painful • Worsening pain while exercising tends to be PFPS, while pain at start of exercise, and ceasing of exercise tends to be Patella tendinopathy • Previous injury to the knee predisposes one to PFPS • Any effusion around the knee >15ml of fluid will switch off VMO (major stabiliser of the knee) increasing the risk of adverse knee mechanics and therefore PFPS • Assess the patella position relative to the painfree side
Patella tendinopathy • Mostly involves jumping/ multidirectional sports • Significantly more painful with eccentric loading rather than any other type of loading • Pain is inferior pole of the patella, or the tendon • Pain is always bad in the morning • Chronic tendinopathy can take 3-6 months to settle • Surgery is only indicated after a considered and lengthy conservative programme has failed
Lateral knee pain • Mostly due to Ilitobial band friction syndrome (ITBFS) • Repeated flexion/ extension at the knee causes ITB to rub on the lateral epicondyle • Training errors and biomechanical problems are the major causes of ITBFS • Occasionally biceps femoris tendon can become inflamed and tender • Superior tib-fib joint can also give lateral knee pain • OA of the lateral compartment • Nerve root irritation/ entrapment
Medial knee pain • PFPS • Medial meniscal injury • OA of the medial compartment • Pesanserinus bursitis • Referred pain
Posterior knee pain • Biceps femoris, gastrocnemius or popliteus tendinopathy • Referred pain • Baker’s cyst • Posterolateral corner injury • DVT • Claudication
Advice to you as GPs • If it’s swollen, refer to orthopaedics • If it’s anterior knee pain, always refer to physio • If it’s giving way, refer to orthopaedics • A painless click is not a problem, as long as no locking or giving way is associated. • Kids with Osgood’s should rest when sore, and try to get strong when condition is stable • Rest will NEVER fix an injury. • Cycling (not standing on the pedals) is generally a knee friendly sport. Running is not.