Knee orthopaedics and trauma Flashcards
What could predispose to early OA in the knee?
Previous meniscal tears
Ligament injuries (especially ACL deficiency)
Malalignment (genu varum > medial OA, genu valgum > lateral OA)
What treatment may benefit a young patient with isolated medial compartment OA?
Osteotomy of the proximal tibia, to shift load onto the lateral compartment
In which patients might knee replacement be considered?
Patients with substantial pain and disability where conservative management is no longer effective
What kind of knee replacements are there?
Total knee replacement - all three surfaces of the knee replaced
Partial knee replacement - unicompartmental replacement or patellofemoral replacement
What is the usual mechanism of injury in a meniscal tear?
Twisting force on a loaded knee
Usually sporting injury in younger patients or atraumatic spontaneous degenerate tears in older patients (over 40)
How should a suspected meniscal tear be investigated?
MRI
What would indicate a meniscal tear on examination of the knee?
Patient reports pain to the medial (majority) or lateral joint line
Effusion develops the next day
Pain on tibial rotation
Catching sensation or “locking” where they have difficulty straightening the knee with a 15° or so block to full extension
Patients knees may feel about to give way if a loose meniscal fragment is caught in the knee when walking
What is the definition of true knee locking?
Mechanical block to full extension caused by a completely torn meniscus flipping over and becoming stuck in the joint line
Which kind of meniscal tear will not heal?
Radial
What is ‘pseudo-locking’ in the knee?
Difficulty in straigtening the joint e.g. in arthritis
This is not a full block to extension i.e. this is not a clinical sign of a meniscal tear
What other injury occurs in up to 25% of anterior cruciate ligament injuries?
Meniscal tear
Which kind of meniscal tear can cause true knee locking?
Bucket handle tear
What is the likely cause of a meniscal tear in an older patient?
Degenerative meniscal tear
How can a degenerative meniscal tear be distinguished from an acute injury?
A degenerative meniscal tear will be Steinmanns negative
Degenerative tears associated with early signs of OA
Why do meniscal tears have limited healing potential?
Only has blood supply to the peripheral 1/3
What are the only meniscal tears that should be considered for meniscal repair?
Relatively fresh longitudinal tears involving the outer 1/3 of the meniscus in a younger patient
What treatment may help the early symtpoms of degenerative meniscal tears?
Steriod injections
Which meniscal tears should be referred for arthroscopic meniscectomy?
Radial tears
Chronic tears
Irrepairable tears
Failed meniscal repair
What is the principal complaint in ACL rupture?
Rotationary instability with giving way on turning
What would indicate an ACL rupture on examination of the knee?
Knee swelling
Excessive anterior translation of the tibia on the anterior drawer test and Lachman test
What is the rule of thirds in ACL?
1/3 people compensate and are able to function well
1/3 can avoid instability by avoiding certain activities or manoevres
1/3 do not compensate and have frequent instability or can’t get back to high impact sport
What percentage of ACL ruptures end up having reconstruction?
40%
What does an ACL reconstruction involve?
A tendon graft (usually patellar tendon or semitendinosis & gracilis autograft) being passed through tibial and femoral tunnels at the usual location of the ACL in the knee and secured to the bone
Intesive rehab - 3/12 - 1 year
What is the mechanism of injury in PCL rupture?
Direct blow to anterior tibia (dashboard/motorbike)
Hyperextension injury
What are the three grades of knee ligament injury?
Grade 1: sprain - some fibres torn but macrostructure intact
Grade 2: partial tear - some fascicles disrupted
Grade 3: complete tear
What is the healing prognosis for a medial collateral ligament tear?
Usually heals well even if complete tear
Unless combined with ACL/PCL rupture
How are acute MCL tears usually treated?
Hinged knee brace
What treatment is avaliable for chronic MCL instability?
MCL tightening
Reconstruction with tendon graft
Damage to which nerve is associated with LCL rupture?
Common peroneal nerve
What is the usual treatment for LCL rupture?
Early repair or late reconstruction with a tendon graft
What are the complications associated with total knee dislocation?
Popliteal artery injury (tear, intimal tera & thrombosis)
Nerve injury – common peroneal nerve
Compartment syndrome
Tear of all four ligaments
Why must regular foot examinations be undertaken following a total knee dislocation?
Intimal tears may occur causing thrombosis
Vascular status of foot must be monitored
What is the treatment for total knee dislocation?
Emergency reduction
External fixation for stabilisation
Mulitple ligament reconstruction
What can cause an osteochondral injury?
Impaction or shear of the articular surfaces or due to a direct blow
What investigations should be done for suspected osteochondral injury?
Xray
MRI
Arthroscopy
How should acute injuries with large oestochondral fragments and substantial amounts of bone be managed?
Fixation with pins
What management option is availiable If a defect due to osteochondral injury has bare bone at its base?
Microfracture - holes can be drilled into the defect to induce bleeding and encourage formation of fibrocartilidge, scar type hyaline cartilidge, to repair the defect
What are the components of the extensor mechanism of the knee?
Tibial tuberosity
Patellar tendon,
Patella
Quadriceps tendon
Quadriceps muscles
What are some predisposing factors to development of extensor mechanism rupture?
History of tendonitis
Chronic steroid use or abuse (body builders)
Diabetes
Rheumatoid arthritis
Chronic renal failure
What kind of injuries can cause ruputre of the patellar tendon or the quadriceps tendon?
Rapid contractile force which can occur after lifting a heavy weight, after a fall or spontaneously in a severely degenerate tendon
Which patients are more likely to have patellar or quadriceps tendon rupture?
Younger - patellar tendon (<40)
Older - quadriceps tendon (>40)
Why should steroid injections for tendonitis of extensor mechanism be avoided?
High predisposition to tendon rupture
What signs might extensor mechanism rupture show on examination?
Difficulty with straight leg raise test
Palpable gap in extensor mechanism
How might extensor mechanism rupture show on Xray?
Low lying patella (quadriceps tendon rupture)
High lying patella (patellar tendon rupture)
What is patellofemoral dysfunction?
It describes disorders of the patellofemoral articulation resulting in anterior knee pain
What are some of the symptoms of patellofemoral dysfuncton?
Anterior knee pain - worse going downhill
‘Clicking’ or grinding sensation at front of knee
Stiffness after prologned sitting causing psuedolocking
What are some predisposing factors to patellofemoral dysfunction?
Female
Adolescence
Femoral neck anteversion
Genu valgum
Joint hypermobility
What can cause the anterior knee pain in patellofemoral dysfunction?
The pull of the quadriceps muscle tends to pull the patella in a slight lateral direction: in some people, excessive lateral force produces anterior knee pain and the lateral facet of the patella is compressed against the lateral wall of the distal femoral trochlea
Chondromalacia patellae (softening of the hyaline cartilage)
What is the treatment for patellofemoral dysfunction?
Physiotherapy
Surgery as a last resort - either releasing a tight lateral retinaculum or if there is a relatively lateralized tibial tubercle, a tibial tubercle transfer to aid patellar trackin
Which way does the patella tend to dislocate?
Laterally
