Intra-articular lesions caused by fat pad hypertrophy

INTRA~ARTICULAR LESIONS CAUSED BY FAT PAD HYPERTROPHY JAMES K. STACK, M.D. AND STEPHEN CHASTEN, M.D. Chicago, Illinois

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IBLIOGRAPHIC research is extremely disappointing with regard to the subject of fat pad hypertrophy (Hoffa’s disease) and its reIationship to interna derangements of the knee. From the year 1905 to the present time IittIe mention is made of this disease in the Iiterature; although some references use the name in their titIe, in discussion they fail to be very cIear as to the nature of the essentiat Iesion and its compIications. From the year 1905 to 1948 there have been approximately thirteen papers devoted to this subject, mostly case reports, indicating either the extinct state of the condition or unwillingness on the part of the surgeon to recognize it in the differential diagnosis of interna derangement of the knee. It may be of course that the condition is so wideIy known and generaIIy accepted that its introduction at this time is not necessary. This is a controversia1 subject and some of our colteagues white denying the fat pad any roIe in knee joint derangement will agree that on many occasions they have performed arthrotomies and not found the torn meniscus listed as the preoperative diagnosis. After inspection of the joint it was closed and for some reason or other the patient was thereafter relieved of his symptoms. The point is that adequate inspection of the knee cannot be made through the usual menisectomy incision without excising the greater part of the fat pad. One cannot see a11 the intercondyIar notch and anterior crucial ligament and certainly one wouId not be in a position to rule out a “bucket-handle” tear of the IateraI meniscus which as we know may at times simuIate very cIoseIy a media1 Iesion. These patients got we11 because they were sustaining intermittent intrusion of tongue-like projections into the working surface of the joint and excision of the fat pad was the answer. On January 4, 1904, Albert Hoffa presented his paper on “The Influence of Adipose Tissue with Regard to the PathoIogy of the Knee Joint” in Berlin, after which his name was 570

associated with enlargement of the subpatellar fat pad and the concomitant synovitis and effusion that so frequently accompany it. This same paper was Iater read at the Fifty-fifth AnnuaI Meeting of the American MedicaI Association, September I 7, 1904. OriginaIIy the first description of disturbance of fatty tissue of the knee was made by Johannes MiiIIer and received the term “Arborescent Lipoma.” It was at that time depicted aS an exuberant growth of fatty viIIi sometimes to such an extent that it compIeteIy fiIIed the knee joint and caused stretching of the joint capsuIe. In these earIy descriptions the Iipomas found in the joint varied in size from that of a cherry to a waInut and were generaIIy Iocated on the media1 aspect of the knee, with or without a pedicIe permitting it to intrude into the working joint surfaces. It was thought that trauma pIayed an important role when eIements of the fat pad became impinged. The trauma was responsible for spIitting thin synovial Iayers thus causing escape of subsynovia1 fatty tissue into the free joint area. Hoffa’s first experience with fat pad hypertrophy occurred during an arthrotomy for meniscus detachment. The meniscus was found to be intact and the fat pad to be responsibIe for the patient’s symptoms. We believe from a study of many microscopic sections of this tissue that fatty hypertrophy is in most instances not a true Iipoma but rather an inflammatory hyperpIasia. Repeated Iowgrade traumas wiI1 bring it about; and when the thin synovial membrane is ruptured by a single vioIence or eroded by repeated minor pinchings, the subsynovia1 fat may exude and thus set the stage for subsequent intrusion and damage to the cartiraginous surfaces. There is nothing to add to the origina description of this pad. Its presence is constant in the human knee but its size and contour are not. Like the cruciaI Iigaments it is infra-articuIar but normaIIy extrasynovia1. It is covered by a thin synovial refIection on its inner surface and is attached on the other side to the deeper sur-

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face of the patellar tendon. There is no relationship apparent between the size of the fat pad and the amount of genera1 body fat in an individua1. The tongue-Iike projections on the articular side will vary in size and enjoy a considerabIe range of freedom. (Fig. I.) This is a report of fourteen patients with knee joint derangement in which the essential lesion was in the fat pad. The condition varied as foIlows : I. Aborescent Lipoma-Two. In both cases the amount of fat was great enough to produce severe changes in the articuIar surface of the patella and underlying femur. In one a pateIIectomy was necessary and in the other a dkbridement of the articular cartiIaginous surfaces 2. Anterior Bulge of Hypertrophic Fat-One. The preoperative diagnosis in this instance was that of ganglion arising from the sheath of the patellar tendon. On inspection of the anterior aspect of the tendon it was found to be normal and was being displaced by a mass beneath it. The tendon was then spIit IongitudinalIy and the fatty mass exuded. Excision of the greater part of the pad could be accomplished through this exposure. 3. Femoral .Tibial Intrusion of Fat Pad with Cartilaginous Lesions on the Femur or Tibia, or Both-Nine. These were the patients who had intermittent recurrence of pain, Iocking and effusion. 4. Femoral Tibia1 Intrusion without An>, Articular Surface Lesion-Two. These were the acute cases occurring after torsion violence which could not be distinguished clinically from rupture of the media1 meniscus. Trauma is certainly a factor in the production of this cIinica1 picture aIthough in the case of true aborescent Iipoma it probably couId not be assigned a role in the production of symptoms. Trauma may be a fal1 on the knee, sudden jerking or torsion of the knee, producing stranguIation of the irreguIar surfaces between the femur and the tibia. The pain is usuaIIy located mediaIly over the joint surface and in acute cases both flexion and extension wiII be restricted by pain, effusion or hemorrhage. CompIete extension wiI1 not be obtained even after the acute signs have subsided if a tongue-Iike projection remains impinged. In oIder patients quadriceps atrophy wiI1 be noted as in many other types of internal derangement. There may be visibIe sweIIing in the chronic cases on both November,

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FIG. I. A, sagittaI view of knee showing extension of fat pad between the pateIla and femur and between the tibia and femur; B, front view showing area of chondromaIacia produced by recurrent intrusion of fat pad between articuIar surfaces.

sides of the patellar ligament. This swelling will be more prominent nearer the insertion of the tendon on the tibia than its origin on the pateIIa. A pseudofluctuance may be created. The tenderness may not be an important sign after acute inflammation has subsided. When the knee is opened, using the usual meniscotomy incision, the fat pad immediately comes into view. If the joint is inspected before the normaI relation of the pad is disturbed by retractors, it will be noted that a tongue-like projection intrudes usuaIIy between the femoral condyIe and the media1 portion of the tibia1 pIateau. In recurring cases this tissue may be flattened, grayish white, firmer than normal and at the point of impingement with the knee in complete extension, signs of erosion wiI1 be evident on the femora1 condyIe. This cartiIage u-i11 be excavated with some undermining of the edges and frequentIy radiaI cracks extending from the center. It wiI1 be less glistening and duIIer in coIor and a dkbridement of this area can be accomplished through this approach. In acute cases the offending portion of fat may be hyperemic or dark enough to be considered hemorrhagic or even gangrenous as the case may be.

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FIG. 2. Increase in papilIary formation of synovial surface of fat pad. The subsynovial fat and connective tissue is the site of chronic inffammatory change with increased fibrosis and chromotropic degeneration.

FoIIowing are typica exampIes of acute and chronic Iesions of the fat pad seen in this series: CASE I. L. G., a fifty-five year oId white’female, 5 feet 4 inches taI1, weighing 130 pounds, was admitted to Passavant MemoriaI HospitaI compIaining of a painfur right knee of three years’ duration. The history described an acute onset when the knee “gave way” whiIe she was descending a staircase. No previous troubIe with the knee had been experienced. The remainder of the history and genera1 physica examination did not contribute to the diagnosis. On walking she had a definite Iimp due to inabihty to straighten the knee compIeteIy and her desire to shorten the stance phase of gait as much as possibIe. Theie was a sIight diffuse effusion throughout the joint and quadriceps bursa but not enough to make the pateIIa baIIotabIe. There was definite tenderness over the media1 aspect of the joint surface more anteriorIy than IateraIIy. FIexion was Iimited sIightIy, probabIy by effusion of the joint, but extension couId not be compIeted through the fina 15 degrees. Arthrotomy was performed through a menisectomy incision and a moderate amount of bIoodtinged ffuid exuded. The synovia1 membrane covering the fat pad was injected everywhere and a tongue-Eke projection of fat, goIden orange in coIor, with many smaI1 areas of hemorrhage and cIots scattered over its surface, was found impinged between the media1 femora1 condyIe and tibia. A sub-tota excision of the fat pad was done and the media1 and centraI compartments of the knee investigated. No other abnormahty couId be found. Her postoperative course was uneventful and she has remained welI. (Fig. 2,) CASE II. W. K., a twenty-nine year oId white maIe, 6 feet 2 inches in height, weighing 210 pounds, was admitted to Passavant MemoriaI HospitaI in March, 1947. He told of having injured his Ieft knee twelve years before when he tripped and feII

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while running a hurdle race. Apparently the injury was a combination of direct vioIence to the knee on the hurdIe and a torsion vioIence during the faI1. He recovered from the episode without any specific treatment but since that time folIowing sIight trauma to the knee it wouId react by pain, swelling and subsequent disability which he believed was out of all proportion to the vioIence. Two weeks prior to his admission the above triad of symptoms reappeared folIowing a minor twist and the swelling, pain and Iocking faiIed to subside following home treatment of rest, heat and protected weight-bearing. When examined he had a definite Iimp due to maintenance of the knee in partiaI flexion. A moderate effusion was present and tenderness was ehcited over the medial margin of the patelIar tendon and over the anterior aspect of the joint surface. FIexion was limited to go degrees and extension to 160 degrees. Neither the x-rays nor remainder of the history and physica examination were heIpfu1. Arthrotomy of the left knee was performed through the usual menisectomy incision and two tongue-Iike projections were immediateIy seen extending from a fat pad which fiIIed the entire intercondyIar space to the joint surface between the media1 femora1 condyIe and the tibia. FoIlowing removal of the projections and remainder of the fat pad a defect the size of a quarter was seen on the femora1 condyle which correspopded exactIy to the point of intrusion. Inspection of the joint reveaIed no other abnormaIity, his postoperative course was uneventful and he has remained weII. In both these instances the gross and microscopic appearance of the fat and underIying synovial Iayer corresponded to that described earIier in the paper. We think this condition of fat pad hypertrophy and intrusion is a definite entity and shouId be considered in the differential diagnosis of interna derangements of the knee. It is not simpIy a convenient wastebasket to be used when arthrotomy faiIs to reveal other causes of derangement. Since the size and shape of the pad varies in individuaIs, so too the trauma that it sustains wiI1 vary as will its response to this trauma. It is of course not easy to make a cIearcut diagnosis of this condition preoperatively unIess pneumoarthrograms are avaiIabIe, but we have had IittIe experience with this diagnostic measure. There are occasions when this condition may be treated conservativeIy as minor impingements wiII respond to rest and heat. The sweIIing at the point of intrusion wiI1 recede and the fat pad wil1 return to norma with minor fibrotic change foIIowing.

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We have had severa such instances; but since they have not been proven at operation, they are not included in this group.

REFERENCES I. HOFFA, A. Sclerosis

of the anterior fat pad x-ray diagnosis. Fortschr. a. d. Geh. d Rontgenstrablen, 36: 646-651, 1927. 2. ESTELLA Y BERMUDEX DE CASTRO, J. and L. Traumatic Hoffa’s disease Roentgen and histologic study; three cases. Arch. de Med. ciry especia!id., 35: 204-16, 1932. 3. DEL VALLE, D. and SATANOWSKY, S. Two cases Hoffa’s disease. Bol. y trab., Sot. de cir. de Biienos Aires, 16: 576-589, 1932. JEAN, G. One case: painfu1 traumatic hypertrophy of subpatellar fatty tissue. Rev. d’ ortbop., ‘9: 548-552, 1932. 4. ESTELLA, J. and RUIX, A. SurgicaI therapy of Hoffa’s disease: one case. Arch. FAC de Med. de Zurapoza, I: 37-43, 1932.

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5. HIPS, H. E. Hoffa’s disease and ext. cart. injury in same knee. Am. J. Surg., 19: 545-548, 1933. 6. HOLLDOCK, F. Surgical findings and results of surgical therapy of injuries of the knee-meniscal injuries-Hoffa’s disease. Zentralbl. Cbir., 65: 126. 139, 1938. 7. BASSET, A. and LE BREGAUD, H. One case abrorescent Iipoma likened to Hoffa’s discnsc. M&n. Acad. de cbir., 68: 210-2I5, ,942. 8. NORSK, M. F. A case of Hoffa’s disease (fibrous inff ammation-like hyperplasia of fatty tissue under the fig. patella). Laegevidensk Kristiana, 1905-5R. 9. SENN, N. Lipoma arborescens of the knee. Ann. Surg., 40: 605, 1904. 10. STEINDLER, A. Synovectomy and fat pad removal in the knee joint. J. A. M. A., 84: 16, ,925. II. RYERSON, E. Lipoma of the prevertebral triangle of the knee. J. A. M. A., 46: 1905. 12. HOFFA, A. The influence of the adipose tissue with regard to the pathology of the knee joint. Berl. klin. Wcbnscbr., 1904. 13. Hoffa’s original paper translation. J. A. %I. A., 43: 793-797,

1904.