Cases of fibrofatty replacement of the quadriceps muscles following
repeated intramuscular injections into the thighs of infants and young
children are being reported with increasing frequency. In such cases, the
knee shows progressive painless limitation of flexion, habitual dislocation
of the patella, or both. The recommended treatment is surgical release,
done early before secondary adaptive changes occur in the soft tissues,
cartilage, and bones comprising the joint. Full flexion should be obtained
at the time of surgery. In children, the lag in extension that follows
extensive release will usually disappear spontaneously.