- See:
Subluxation of the Patella
- Fulkerson Classification:
- type I,
subluxation alone;
- type II, subluxation and tilt;
- type III, tilt alone;
- type IV, no malalignment;
- Clinical Presentation:
- anterior knee pain with a tight, tender lateral retinaculum;
- patients also demonstrate decreased passive medial patellar excursion
(normal is 15 deg) and may be associated w/ a
bipartite patella;
- Examination:
- retinacular tenderness;
- pain on patellar compression
-
instability;
- passive patellar tilt test and the patellar glide test assess tightness/laxity of
lateral and medal retinacula, respectively;
- patellar tracking is assessed during knee flexion & extension, & presences/
absence of J sign;
-
Q angle:
- Radiographs:
-
Axial View
- because increased flexion results in reduction of subluxated patella,
x-rays be obtained w/ in 20 and 45 degrees of flexion;
-
merchant angle of congruence:
- used to evaluate
subluxation;
- Laurin technique:
- lateral patellofemoral angle is index of tilt but not of subluxation;
- patellar alignment assessed using lateral patellofemoral angle on axial
views, made w/ knee in 20 deg of flexion;
- angle formed by lateral patellar facet & line drawn across most
prominent aspects of anterior portion of femoral trochlea should
be open laterally in normal patellofemoral joint;
- CT scan:
- may reproduce patellofemoral relationships including normal alignment, lateral
patellar tilt, and patellar
subluxation;
- CT scanning should be reserved for those difficult cases in which plain
radiographs are indeterminate;
- CT images are taken thru the first 45 deg of knee flexion;
- taken at 0 deg, 15 deg, 30 deg, and 45 deg of flexion;
- use the posterior condyles as a reference line for determining tilt;
- patellar tilt is present if a line drawn along the lateral patellar facet and a line drawn along
the posterior femoral condyles is less than 12 deg;
- references:
Computerized tomography of the patellofemoral joint before and after lateral release or realignment.
Fulkerson JP, Schutzer SF, Ramsby GR. Arthroscopy 3: 19-24, 1987.
CT determination of tibial tubercle lateralization in patients presenting with anterior knee pain.
Skeletal Radiology.
24: 505-509. 1995.
- Surgical Treatment:
-
Distal Realignment Procedures:
- as noted by Morshuis et al, distal realignment procedures result in satisfactory
results in about 2/3 patients who have patellofemoral pain and x-ray
evidence of arthrosis but nearly all patients w/ patellofemoral pain w/o
x-ray evidence of arthrosis had good or excellent results;
-
Lateral Retinacular Release:
- release detaches lateral retinaculum, fibers from
tensa fascia lata &
joint capsule;
- indications:
- pts demonstrating tightness of lateral retinaculum (patella tilt test);
-
Patella Alta,
chondromalacia, increased
Q angle, & an
atrophic trochlear groove are not indications for lateral release;
- post op:
- aggressive ROM is needed to prevent scarring and tightening along
released
lateral structures;
Clinical prognosticators for the efficacy of retinacular release surgery
to treat patellofemoral pain.
Biomechanical effects of different surgical procedures on the extensor
mechanism of the patellofemoral joint.
Pathomechanics of the femoropatellar joint following total knee arthroplasty.
Treatment of patellofemoral instability in Down's syndrome.
The early diagnosis and treatment of developmental patella infera syndrome.
Patellofemoral contact pressures. The influence of q-angle and
tendofemoral contact.
Elevation of the insertion of the patellar ligament for patellofemoral pain.
Patellar pain and incongruence. I: Measurements of incongruence.
Patellar pain and incongruence. II: Clinical application.
Anatomy of the junction
of the vastus lateralis tendon and the patella.
Disorders of patellofemoral alignment.
JP Fulkerson and KP Shea.
JBJS. Vol 72-A. 1990. p 1424-1429.
