Convert to ICD-10-CM: 
726.64 converts approximately to:
- 2015/16 ICD-10-CM M76.50 Patellar tendinitis, unspecified knee
 ICD-9-CM Volume 2 Index entries containing back-references to 
726.64:
- Tendinitis, tendonitis (see also Tenosynovitis) 726.90  patellar 726.64 patellar 726.64