Digital Radiography sometimes is not enough!

The radiograph posted below corresponds to a 20yo thoroughbred gelding that presented for chronic lameness in the left hind limb. Physical exam revealed moderate effusion (swelling) within the left stifle (specifically, the medial femorotibial and femoro-patellar joint spaces). The gelding was a grade 4/5 lame at the trot and resented flexion of the left stifle/hock. Radiographic exam (3 standard views ) of the left stifle revealed mild to moderate arthritis of the medial femorotibial joint space, however, these findings did not explain the severity of the lameness and the degree of swelling associated with the stifle joint.

Due to the lack of findings in the radiographic exam, the left stifle joint was examined via ultrasound. Several significant findings were noted (below image). These included significant fluid within the stifle joint (medial femorotibial joint), bulging medial meniscus, and a smoothly-defined bone fragmment/protuberance of unknown origin. The "bulging" meniscus  was consistent with significant inflammation of the meniscus which could explain the accumulation of fluid within the joint and the degree of lameness recorded during the exam.

The bone fragment/protuberance that was first visualized with the ultrasound required additional radiographic views that are not typically taken of the stifle joint. An osteochondroma was diagnosed based on the ultrasound and the additional radiographic views. Also called osteocartilaginous exostoses, osteochondromas are overgrowths of cartilage and bone near the end of the bone and near the growth plate. The stifle was treated with a cortisone derivative and sodium hyaluronate. Two weeks post-injections, the effusion was significantly diminished and the gelding's lameness was reduced from a grade 4 to a 1 out of 5. This case is a good example of the benefit of digital radiography and ultrasound when evaluating a complex anatomical structure such as the equine stifle.