The stitches on the back and left side of Howard Cadle's head were removed last week. Bruises and welts on the shoulders and back of the 16-year-old Fairfax County runaway are starting to fade. What has not faded is the question of whether three Fairfax County policemen used excessive force in arresting the youth on Jan. 6.

Witnesses to the arrest in the backroom of the Franconia Roller Rink said they saw policemen hit Cadle repeatedly on the head and shoulders with their billy clubs.

As a result, the youth's father, Lacy Cadle, has filed brutality charges against the officers involved, and the internal affairs division of the Fairfax County Police Department has begun an investigation of the incident. Because the police department considers the investigation confidential, Cpl. Edward Mould of the internal affairs division has refused to give a police account of what happened after the policeman went to the roller rink Jan. 6 with an order to arrest Cadle and take him to a county detention home.

The youth had violated his probation for a house burglary by running away from home earlier in the week, police said. Cadle has run away from home "9 or 10 times," according to his father.

At the roller rink, an officer asked Pat Currence, a rink employee, if she knew where Cadle was, Mrs. Currence said yesterday. She said she located the youth and turned him over to the policeman, who took him into the rink's storeroom.

Mrs. Currence said a few minutes later her daughter, also a rink employee came running to her, yelling that the police were beating up Cadle.

Mrs. Currence said she ran to the storeroom and found two policemen beating Cadle, who is 5 feet 11 and weighs 155 pounds, on the head with their billy clubs. She screamed at the policemen, she recalled, "What the hell do you think you're doing? Don't beat that kid."

Cadle said he was taken to the storeroom, told to "spread-eagle" against the wall and then was kneed in the groin when he tried to turn away from the wall.

"Then, when I bent over, they started beating me with the clubs," Cadle said. He was wearing roller skates at the time, and he had to struggle to keep on his feet two witnesses said.

The commotion attracted a crowd of about 50 teen-agers on roller skates to the storeroom door. Mike Stinnett, a floor guard at the rink, said he and another floor guard had to struggle to keep the teen-agers from rushing into the storeroom. Stinnett said the crowd was angry and teen-agers were yelling at the policemen to "stop hitting" Cadle.

After Mrs. Currence yelled at the policemen, she said, they handcuffed Cadle and led him outside. She said the police ignored Cadle's request to take off his skates.

Outside the rink, according to Stinnett, Cadle slipped on his skates and fell. Cadle says a policeman kicked him in the left side after he fell to the asphalt.

Stinnett said that with the policemen's permission he picked Cadle up, sat him down a nearby block of wood and helped him change from skates to his street shoes. Stinnett said Cadle was bleeding heavily from the back and left side of his head.

Police took Cadle to the nearby Franconia substation for about 15 minutes, then an ambulance took him to Mount Vernon Hospital. He was treated there for scalp cuts and multiple bruises around the shoulders and back. Three stitches were taken to close the cut on the back of his head and two to close the cut on the side. Skull X-rays disclosed no fractures, but Cadle was referred to a neurologist for further tests, a hospital spokesman said.

None of the policemen involved in the alleged beating is permitted by the police department to comment on the incident.

Cadle gave a statement Friday to internal affairs officers about the incident. He said last week he is suffering from headaches and has lost some sight in his left eye and some hearing in his left ear. His father said Friday that his son has not yet seen a neurologist.

A police department source said witnesses to the incident are being interviewed and that a determination on whether the three officers used excessive force in the arrest should be made within two weeks. Department policy requires officers to use only the "degree of force necessary to overcome any resistance."

No action has been taken against the three police officers involved. Deputy Chief Kenneth Wilson said that police regulations require the internal affairs division to investigate all allegations of police brutality.