Case Study

Glimpses on Cystic Swellings around the Knee

Thulasivasudevaiah Narayan*, Harish kumar P, Deepak Naik , Pankaja SS and Rohith Muddasetty

Associate professor, Department of surgery, JSS hospital, India
Assistant Professors, Department of surgery, JSS hospital, India
Senior Resident, Department of surgery, JSS hospital, India

Published Date: 05/04/2021

*Corresponding author: Thulasivasudevaiah Narayan, Department of surgery, JSS hospital - JSSAHER, MG road, Mysore-04, India

DOI: 10.51931/OAJCS.2021.02.000023


The most common presenting complaints in the orthopaedic Out-patient department are knee pain due to osteoarthritis. Many patients present with swelling around the knee due to benign disorders. The majority of the swellings are cystic in nature and the differential diagnosis depends on the anatomical location of the cystic swelling and the radiological findings. We made an attempt to discuss the presenting clinical features, investigations, and operative findings among the few knee swellings presented in the surgical wards. The most common cyst in relation to the knee is Baker’s cyst, semi- membranous bursa, ganglion cysts. In our discussion we are excluding the acute inflammatory diseases of knee namely septic arthritis, cellulitis/abscess around the knee. A case of Ganglion cyst of the peroneal nerve and other cystic swellings were presented in this article.

Keywords: Ganglion cyst; Peroneal nerve; Baker’s cyst; Epidermoid, Bursa; UGAFI


Cystic swellings around the knee are benign in nature; some of them are due to chronic inflammatory pathology. To understand the diagnostic criteria, we present different types of cysts around the knee. All patients were evaluated pre-operatively by taking detailed history and clinical findings were recorded and subjected for surgical excision. The patients were followed up for a minimum period of 4 weeks and the Biopsy findings were noted.

 Case Summary-1

A 54-year-old male presented with history of swelling over the front of right knee for 6 months. He has noticed the swelling following injury over the right knee, which was gradually increased in size over a period of 6 months. He has noticed pain and skin changes (scaling) for 15 days. On admission his vitals were stable with BP-130/80 mm of Hg. Local examination of right knee showed an irregular well-defined swelling of ,8cm X 6 cm with bosselated surface and thinning of overlying skin due to stretching (Figure 1). It was tender with variable consistency. The knee joint mobility was normal.

There was free mobility over the underlying patella (Figure 1). The inguinal lymph nodes were not enlarged. A clinical diagnosis of pre patellar Implantation dermoid cyst was made. The Cystic lesion was excised through an elliptical incision under spinal anaesthesia. There was pultaceous material drained from the ruptured thin wall of the cyst. The resulting wound closed primarily. The Histopathology revealed features of chronic granulomatous lesion. The sutures were removed on 14th day, with good scar.

Figure 1: Implatation dermoid.

Figure 2: Pre patellar Bursa.

Figure 3a: Ganglion of peroneal Nerve.

Figure 3b: Peroperative image of Ganglion of peroneal N.

Figure 4: Baker’s Cyst - right knee.

Figure 5: Varicose veins -SSV

Case Summary-2

A 40-year-old male presented with a swelling over the right knee for 1 year duration. It was painless, with no history of trauma. On clinical examination it was 5cmX4cm in size, cystic in nature , non-tender, freely mobile over the patella (Figure 2). A clinical diagnosis of pre-patellar bursa was made. The lesion was excised under local anaesthesia. The cyst was containing gelatinous fluid. Post operatively patient was treated with oral Antibiotics and analgesics. Following suture removal on 10th day, the scar was healthy. There were no complications in the post-operative period. Histopathology was not performed as operative findings were suggestive of benign lesion (bursa).

Case Summary-3

A 50-year-old female presented with history of swelling over left lower limb for 6 weeks. She also complained of tingling sensation in the left lower limb since 1 month. She has noticed a swelling over the side of left leg insidiously, with mild pain. She was not a diabetic or hypertensive, and there was no history of trauma. Her blood investigations - Hb%-12.6 g. TC-7000cells/cumm, DC-N-57%,L-37%. Local examination of the left leg showed an elongated slightly tender cystic swelling over the lateral aspect lying about 3 cm below the left knee joint (Figure 3). There was no free mobility of the swelling. It was transilluminant. Ultra sound (surface scan) of the swelling was suggestive of Ganglion cyst of the Common peroneal nerve.Under spinal anaesthesia by a vertical incision along the cyst was dissected from surrounding structures (Figure 2). The cyst wall was very thin and it has ruptured during dissection and gelatinous fluid evacuated from cyst. The cyst wall separated from the peroneal nerve trunk and excised. Wound closed in layers. Post-operative period was uneventful. There was no neurological deficit noted during follow up period.

Case summary – 4

A male patient aged 55 years, who is agriculturist by occupation presented with a swelling over the lateral aspect of right knee for 8 months. There was history of thorn prick while working in the field, following which 2 months later he has noticed a swelling at the site of prick. The clinical examination of the swelling was suggestive of implantation dermoid cyst. It was excised successfully under local anaesthesia. Patient was followed up on OPD basis. HPE was suggestive of dermoid cyst.

Case summary-5

An adult male aged 50 years was admitted with history of swelling over the back of knee for 1 year. There was no history of pain in the swelling; patient says the swelling is more obvious on standing posture. There is no history of knee pain or knee joint swelling. On examination there was a soft cystic swelling in the right popliteal area, measuring 5X4 cm with smooth surface, ill-defined borders. It was less obvious on flexion of the knee. The movements of the right knee were normal. A clinical diagnosis of Baker’s cyst was made (Figure 4). The surface scanning was showing features of infected Baker’s Cyst . The cyst was excised under spinal anaesthesia, and patient was discharged after 3rd day with oral antibiotics. All sutures were removed on 10th day, scar was healthy.


Clinician must be aware of differential diagnosis of the cystic swellings around the knee before requesting for a radiological investigation. The Baker’s cyst is known to all medical students as it is commonly seen in the surgical or orthopaedics OPD. But In our surgical practice many pathological conditions can occur around the knee starting from cellulitis, to osteoarthritis. Patients can present with a pain less swelling around the knee, and most of them are cystic in nature. We made an attempt to describe the cystic swellings presented to our surgical wards with different clinical features. The Clinical diagnosis depends on the anatomical location, and associated history.

The cystic swellings around the knee [1] can be Classified as:

  1. True Cysts.
  2. synovial cysts- Baker’s cyst, Proximal tibiofibular joint.
  3. Ganglia- Gastrocnemius, Popliteus, Peroneal nerve ganglion (Figures 3a & 3b).
  4. Bursa- Prepatellar, Infrapatellar,Pes anseinus,
  5. Meniscal Cyst- Intrameniscal, parameniscal, Synovial
  6. Lesions that mimic cysts

- Haematoma, seroma, Abscess,

-Vascular lesions- Popliteal artery Aneurysm, Varices (Figure 5), Haemangioma

Neoplasms- Synovial sarcoma, peripheral nerve sheath tumor. Myxomatous neoplasms.

The pre-patellar bursa is located anterior to the patella, deep to the subcutaneous soft tissue. Direct trauma to the patella can lead to inflammation of the bursa. This is an example of Housemaid’s knee where the patient will have repetitive injury to bursa.

Ganglion cyst of the peroneal nerve: The common peroneal nerve (CPN) arises from the L4-S1 nerve roots. It gives rise to lateral cutaneous nerve of calf. The CPN provides sensory innervations to the antero-lateral and dorsal aspect of the foot, as well as motor innervations to the anterior and lateral compartment muscles. The CPN divides into superficial and deep peroneal nerve in the fibular tunnel. It can be affected by extra neural compression from the habitual leg crossing, anorexia, previous regional limb surgery with immobilization cast, ganglion or Baker’s cyst.

Intraneural ganglion cysts are benign mucinous lesions in the peroneal nerve [2]. The cause for the development of this cyst is due to tracking of fluid from the joint through a small tear in the joint capsule (Superior tibiofibular joint). They can present with a swelling over the lateral aspect of knee with neuropathy symptoms. Patient can present with parasthesia over the dorsum of foot and foot drop due to intraneural ganglion cyst following trauma [3-6].

There may be associated muscle atrophy in the nerve distribution. Ultrasound examination of the cyst showed multiloculated fluid collection in close relation with common peroneal nerve [4]. The differential diagnosis of the peroneal nerve cyst is Neurilemmoma, Neurofibroma, neuroma. Early diagnosis and appropriate surgical treatment of this condition is a key to good outcome. Delayed diagnosis can lead to partial relief of symptoms [5]. In our case of Ganglion cyst of peroneal nerve left leg, the patient noticed improvement in the movement of foot with disappearance of numbness over the dorsum of foot in 2 weeks after the excision of the cyst.

The Popliteal (Baker’s) cyst is common cystic swelling in the popliteal region due to communication between the posterior joint capsule and the normally occurring gastrocnemius-semimembranosus bursa. They are lined by synovium, may be simple or septated and contain haemorrhage, debris or loose bodies. Many are asymptomatic, they can cause limitation of flexion of knee, and they can rupture with symptoms similar to Deep vein thrombosis of leg. UGAFI- (Ultrasound guided aspiration fenestration and injection) is an effective and safe treatment option for symptomatic popliteal cyst. This is accomplished by aspiration and fenestration by spinal needle followed by injection of 1 ml triamcinolone&2ml of 0.5% Bupivacaine into the decompressed remnant [7].

Implantation dermoid occurs most commonly in the Foot or hand among agriculturist /tailors due to thorn Prick. The swelling is cystic in consistency, fixed to skin, freely mobile over the deeper structures. In our patient the dermoid was over the pre- patellar region with thinning of skin with impending rupture. During surgical excision, the sac was ruptured at thinnest point to drain the pultaceous material. This epidermal inclusion cyst over the pre patellar area can mimic chronic pre-patellar bursitis [8]. The cystic lesions around the knee should be radiologically investigated (Ultrasound /MRI) to know the character of the content. Routine MR Imaging of the cystic swellings in the soft tissues exhibit high signal intensity on T2 –weighted images because of their high content of free water [9].


Acute painful conditions in the knee can be due to infective lesions like cellulitis, pyogenic abscess like in other parts of the lower limb. Cystic swellings in the soft tissues of knee can be provisionally diagnosed due to their anatomical location and clinical findings. Most of the cystic lesions are superficial and they require MRI imaging studies to know the character of contents. These cystic lesions are amenable to excision with good post-operative results. Careful dissection is necessary in case of peroneal nerve ganglion cyst.


Informed consent has been taken from the above patients for utilizing the images for the purpose of publication in medical journals.


Dr Rohith Muddasetty – Senior Resident JSSMC, Dr Thrishuli PB -Associate Prof JSSMC.

Conflicts of interest


Funding sources

No financial support/No sponsorship


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