Quadriceps myofibrosis. A complication of intramuscular injections.

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.