A 49-year-old Caucasian man presented with a six-month history of progressively worsening right knee pain with associated swelling. The pain was present when the patient was at rest, and worsened when the leg was bearing weight, thus restricting his walking to short distances. His knee had become increasingly swollen. He denied any symptomatic night pain, locking, or a giving way of his knee. The patient was otherwise fit and well. His medical history was unremarkable and he was only taking ibuprofen for the pain.
Upon examination, the patient was seen to have marked quadriceps wasting of his right lower limb and a visibly swollen popliteal fossa. On palpation the swelling was hard, non-mobile, well defined, and measured 4 × 8 cm. The swelling was non-tender and there were no associated skin changes. Conversely, the patient had tenderness over the medial joint line. He could fully extend his knee, but flexion was restricted to only 115 degrees. There was no ligamentous instability and a McMurray test proved equivocal. An examination of the patient's hip revealed no abnormality.
A plain radiograph of the patient's knee revealed multiple calcific densities within the soft tissues surrounding it (Figure ). Although some of these appeared to lie within the capsule, the majority appeared to be outside of it. These appearances were thought to be consistent with idiopathic tumoral calcinosis. However, to further scrutinize these calcifications, a magnetic resonance imaging (MRI) scan was recommended. It showed an extensive thickening of the patient's synovium, multiple intra-articular calcific and ossific loose bodies, and large calcified bursal extensions. The bursal component extended into the patient's posterior distal thigh and his proximal calf. These findings were thought to be consistent with very extensive synovial chondromatosis (Figure ).
Plain radiograph and magnetic resonance imaging scans showing multiple soft tissue calcifications within and outside the joint capsule of the right knee.
The patient's blood tests were normal: corrected calcium was 2.24 mmol/l, parathyroid hormone 2.5 pmol/l, inorganic phosphate 1.17 mmol/l, serum urate 296 μmol/l, white cell count 7.2 × 109/l, and C-reactive protein 4 mg/l.
A two-stage procedure was planned following the findings of the MRI scan. The first stage was arthroscopy, which was able to note Grade IV osteoarthritis alongside florid synovial chondromatosis in the medial compartment (Figure ). There were multiple loose bodies within this compartment and nodules were fixed to the synovium. A synovectomy with debridement and excision of these bodies was thus performed.
An arthroscopic photograph showing nodules of chondromatosis fixed to the synovium.
The second stage involved an open exploration of the patient's popliteal fossa. Three large calcified masses were found, all enclosed in bursal sacs (Figure ). The first was just medial to the posterior tibial nerve; the second was deep into the medial head of the gastrocnemius muscle; and the third was lateral to the semimembranosus at the level of the oblique popliteal ligament. All three masses were excised and the sacs were closed with purse string sutures. A histological review at the Royal National Orthopaedic Hospital in Stanmore, UK confirmed our diagnosis of synovial chondromatosis. The sections showed nests of chondrocytes with focal ossification and focally attenuated synovium overlying the nodules.
An intraoperative photograph showing the extent of the popliteal disease.
After the operation, the patient underwent weekly physiotherapy sessions focusing on quadriceps strengthening, with a daily exercise regime to supplement this. He recovered well and three months after the operation, has regained his right knee's full range of movement with flexion increased to 130 degrees, which is equal to that of his left knee. He has residual medial joint line tenderness, undoubtedly due to osteoarthritis.